unit 4: atomic structure
TRANSCRIPT
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Unit 4:
Atomic Structure (Chapter 4)
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Millikan Oil Drop Experiment
In 1909, the American physicist Robert Millikan measured the charge of an electron using the apparatus below. He introduced a fine mist of oil into the closed chamber. The drops of oil passed between two electrically charged plates through which he was able to influence their rates of descent by varying the voltage between the plates. He observed the drops through a microscope and adjusted the electrical force (voltage) so that drops moved away from the plate which had the same charge as the oil drops. He timed the drops’ rate of movement. From this information he was able to determine the charge of an electron and suggest a value for its mass.
oil bath
x-ray
charged plates
microscope
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The Rutherford Experiment
Our modern view of atomic structure is based on the work of Ernest Rutherford. In his experiment, alpha particles bombarded a sheet of gold foil. The apparatus and the paths followed by those particles are illustrated below.
Pictorial Representations of the Models
John Dalton Billiard Ball Model
J.J. Thomson Plum Pudding Model
Ernest Rutherford Nuclear Model
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History of the Atom
DIRECTIONS: Read pages 101-108 in the Academic Chemistry Textbook, including all sidebars, to garner the information to answer the following questions. 1. What three words did Democritus use to describe the atom? ______________________,
______________________, and _______________________.
2. The word atom, which is derived from the Greek word atomos, means _______________________.
3. What was lacking in Democritus’’ theory? ___________________________________________________
_________________________________________________________________________________________
4. Who transformed Democritus’ ideas into a scientific theory based on experiments? ________________
5. Like Democritus, John Dalton believed that atoms were _______________________ and
_______________________.
6. Dalton’s model of the atom was called the ___________________ ___________________ model.
7. Although much of Dalton’s atomic theory is still accepted today, he could not explain what held the
atoms together in a _______________________.
8. Using a cathode tube that was developed around 1860, J. J. Thomson discovered the
_______________________, which he called corpuscles.
9. How did Thomson know that his particle was negatively charged? _____________________________
________________________________________________________________________________________
10. Since matter is electrically neutral, Thomson realized that something _______________________ also
had to be inside the atom along with the electron. Thomson was the first scientist to describe the
_______________________ nature of the atom.
11. Describe Thomson’s model of the atom. What was it called? ___________________________________
_________________________________________________________________________________________
_______________________________________________________________________________________
12. What ratio did Thomson calculate? _______________________________________________________
13. T/F: All electrons, no matter where they come from are identical? __________________
14. What was the name of the famous experiment that Robert Millikan performed? ___________________
15. Millikan determined the _______________________ carried by an electron. Combining his work with
Thomson’s charge-to-mass ratio, Millikan easily calculated the _______________________ of an
electron.
16. Who designed the Gold Foil Experiment? ________________________________________________
17. What kind of particles did Rutherford shoot at the gold foil? __________________________________.
These particles are _______________________ nuclei.
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18. If the plum pudding model was correct, then the particles should pass straight through the atom with
just a slight deflection. What Rutherford found however, was that _______________________ of the
alpha particles passed ______________ _______________ the gold atoms without deflection and a
few particles were greatly _______________________; but the Nobel Prize recipient was astonished
when he found that one in 20 000 bounced ______________ _______________.
19. Rutherford explained this result by stating that the atom must be mostly __________ ______________
with something very small, extremely _______________________ and _______________________
charged in its center. He called this the _______________________.
20. Rutherford’s model of the atom is referred to as the ______________ _______________.
21. According to Rutherford’s theory, explain the location of the protons, electrons, and neutrons.
_________________________________________________________________________________________
_________________________________________________________________________________________
_________________________________________________________________________________________
22. The three subatomic particles had been discovered by what year? _______________
23. . Millikan found that the electron carries one unit of _______________________ charge with a mass
_______________________ that of a hydrogen atom. The proton carries _______________________
unit of _______________________ charge with a mass _______________________ times that of an
_______________________. The neutron carries _______________________ charge and its mass is
about the same as that of a _______________________.
Properties of Subatomic Particles
Particle
Symbol
Relative Charge
Relative Mass (mass of p
+ = 1)
Actual Mass (g)
Electron
Proton
Neutron
Label each picture with the appropriate scientist and model name.
_____________________ ______________________ ______________________
_____________________ ______________________ ______________________
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Structure of the Atom
The Development of Modern Atomic Theory
I. The earliest models
A. Greeks 1. Approximately 400 BC the Greeks classified matter into four substances — earth, fire, air, and water 2. DEMOCRITUS
a. Greek philosopher who first suggested that matter consisted of small indivisible particles called atoms.
b. Believed that matter could be divided into smaller and smaller particles until a basic particle of matter was reached.
c. Performed no experiments to test his ideas, arrived at conclusion by thinking. B. ALCHEMISTS (400 BC to 1600 AD)
1. Mystics and fakes claiming they could turn cheap metals into silver and gold — called transmutation.
2. Dominated the next two thousand years of chemical history 3. Performed experiments and kept journals but did not openly share their results
C. ROBERT BOYLE – Father of Chemistry 1. first person to perform quantitative physical experiments 2. published a book of his findings, The Skeptical Chemist, in 1661
II. Fundamental Chemical Laws
A. JOSEPH PRIESTLY (1773 – 1804) 1. English clergyman and scientist 2. discovered oxygen in 1774 by hearing mercuric oxide 3. By the late 1700’s, combustion had been studied extensively; the gases carbon dioxide, nitrogen,
hydrogen, and oxygen had been discovered. B. ANTOINE LAVOISIER (1743 — 1794)
1. performed experiments that showed that combustion involved oxygen (which he named) and not phlogiston
2. discovered that life was supported by a process that involved oxygen and was similar to combustion
3. formulated the Law of Conservation of Mass a. performed quantitative experiments and weighed the reactants and products b. found that mass of reactants always equaled the mass of products c. concluded that matter cannot be created or destroyed d. called the Father of Modern Chemistry
e. having been associated with collecting taxes for the government, he was executed on the guillotine as an enemy of the people in 1794
C. JOSEPH PROUST (1754 — 1826) 1. French chemist 2. demonstrated the Law of Definite Proportions
a. a given compound always contains exactly the same proportion of elements by mass. III. First Experimental Atomic Theory
A. JOHN DALTON (1766 — 1844) 1. Dalton’s Atomic Theory – The Billiard Ball Theory
a. Each element is made up of tiny particles called atoms which are indivisible b. The atoms of a given element are identical; the atoms of different elements are different c. Chemical compounds are formed when atoms combine or rearrange with each other. d. Chemical reactions involve reorganization of atoms — changes in the way they are bound
to each other. The atoms themselves are not changed in a chemical reaction. IV. Early experiments to characterize the atom
A. The Electron 1. MICHAEL FARADAY (1791 — 1867)
a. investigated the electrical nature of matter b. disagreed with Dalton’s model of the atom — something had to hold atoms together
c. claimed electricity was the “glue” that held atoms together d. discovered cathode rays
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2. SIR WILLIAM CROOKE
a. developed the Crooke’s tube that produced cathode rays b. noticed that the rays always moved from the cathode to the anode c. found that the rays traveled in straight lines and possessed energy d. conclude that a stream of light was made up of particles
3. J. J. THOMSON (1856 — 1940) a. further studied cathode rays and found that they were repelled by the negative pole of an
electric field — thus, negatively charged. b. credited with the discovery of the electron c. determined the charge to mass ratio of an electron: e/m = —1.76 x 10
8 coulombs/gram
d. concluded that all atoms of all substances contain the same kind of negative particles, and all electrons are identical
e. Thomson’s Model of the Atom — The Plum Pudding Model i. the atom consisted of a positive material with electrons embedded randomly in it ii. called Plum Pudding Model because the electrons were dispersed like raisins in a
pudding (the positive material), as in plum pudding, his favorite English dessert.
f. awarded the Nobel Prize in physics in 1906 (Subsequently, at least seven of his assistants were awarded Nobel Prizes)
4. ROBERT MILLIKAN (1868 — 1953) a. performed the oil-drop experiment to determine the numerical charge on an electron:
-1.60 x 10-19
coulombs b. combined with Thomson’s ratio, calculated the mass of an electron — 9.11 x 10
-28 grams
c. won the Nobel Prize in physics in 1923, first American to do so.
B. The Nuclear Atom 1. EUGENE GOLDSTEIN (1850 — 1930)
a. credited with the discovery of the proton in 1885. Called them “canal rays 2. WILLIAM ROENTGEN (1845 – 1923)
a. discovered penetrating rays given off by cathode ray tubes, which he called x-rays 3. HENRI BEQUEREL (1852 — 1919)
a. discovered radioactivity – the spontaneous decay of an unstable atom nucleus with the release of x-rays, gamma rays, alpha particles, and/or beta particles
b. awarded the Nobel Prize in physics in 1903 4. ERNEST RUTHERFORD (1871 — 1937)
a. 1908 — carried out the gold foil experiment to test Thomson’s model of the atom i. used alpha particles as bullets to probe the atom
(alpha particle = helium nucleus, although Rutherford did not know this)
ii. shot the alpha particles at a thin sheet of gold foil b. based on Thomson’s model, Rutherford predicted the alpha particles would be able to pass
right through the foil. c. Actual results
i. most particles passed straight through ii. some were deflected iii. 1 out of 20 000 were deflected straight back!!!
d. Rutherford’s Model of the Atom — Nuclear Model (1911) i. Atom contains a very dense, very small center of concentrated positive charge,
which he called the nucleus. ii. Atoms are mostly empty space
iii. Electrons must be present in the empty space about the nucleus e. calculated the entire diameter of the atom to be about 10 000 times the diameter of the
nucleus f. won the Nobel Prize in chemistry in 1908
5. JAMES CHADWICK (1891 — 1974) a. discovered the neutron in 1932 b. awarded the Nobel Prize in physics in 1935
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Structure of the Atom Video
1. The word atom comes from the Greek word “atomos,” which means ____________________.
2. Who came up with the very first theory of the atom? ___________________________
3. The alchemists brought about an important change to the field of science because they
began to do __________________________.
4. The Law of Conservation of Mass states that __________________________________________
_________________________________________________________________________________
5. T/F: Dalton believed the atom was indivisible. _______________
6. Dalton and Democritus shared similar ideas about the atom. However, Dalton based his
theory on __________________________.
7. Faraday did not believe that Dalton’s atomic theory was correct because he could not
explain what held atoms together. According to Faraday,
_____________________________ held atoms together in compounds.
8. What subatomic particle did Thomson discover? _________________________
9. According to the video, what is the name of J.J. Thomson’s model of the atom?
______________________________________
10. Who performed the oil drop experiment? ___________________________
11. The charge to mass ratio of an _____________________ was determined from the oil drop
experiment.
12. The alpha particle is suitable for probing the atom because it is ____________________.
13. Why did Rutherford conclude that most of the atom is empty space?
_________________________________________________________________________________
_________________________________________________________________________________
14. What did Ernest Rutherford discover about the atom? _________________________________
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Who Am I? Democritus, Dalton, Thomson, Rutherford, & Millikan
ACROSS
2. Thomson compared his model to ________________, (two words) his favorite dessert 5. Discovered the nucleus 9. Rutherford designed the ________________ (two words) experiment to study the interior of the
atom 11. Thomson studied ________________ (two words) to try to determine what held atoms together 12. Rutherford's model is called the ________________ model 13. his theory could not explain what held the atoms together in a compound 14. Designed the oil drop experiment
DOWN
1. Dalton transformed Democritus’ ideas into a scientific theory based on ______________ 3. Dalton said that the atom is an ________________ sphere of solid material throughout 4. First recorded person to observe and think about the atom, 400 B.C. 6. Dalton compared his atom to a ________________ (two words) 7. Thomson proposed the atom to be positive material with ________________ material embedded
in it 8. Millikan calculated the numerical charge of an ________________ 10. Discovered the electron
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Subatomic Particle Review
Atom - ______________________________________________________________
______________________________________________________________
are _______________________ neutral – have no ________ electrical charge
electrical charges are carried by _________________ particles of matter.
Atoms can be broken down into ________________, fundamental parts called
_____________________ _______________________.
Electrons, _____ : (_____) charge
discovered by ____________________________ in 1897
Protons, ______: (_____) charge
discovered by ____________________________ in 1885
found in the _______________ of the atom
Neutrons, _____: (_____) charge
discovered by ________________________ in 1932
found in the _______________ of the atom
So…..what makes elements different?
___________________________________________________________________
Atomic Number, ______:
the number of _____________ in the nucleus of the atom
_________________ an element
the ________________ _______________ for each element on the PT!
the number of ____________ in a ______________ atom
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EXAMPLE: 1. What is the atomic number of tin? ______________
2. How many protons are in the nucleus of a tin atom? ___________
3. How many electrons are in a neutral tin atom? __________
Mass Number, ______:
counts ________________________
the total number of _______ and ______ in an atom
__________________ be found on the PT!
Shorthand Notation
# p+ = ________________
# e
- = _________________
# n
0 = _________________
gold – 197
*You will need to look up
the __________ # on the PT
atomic # = __________________ = _________________
mass # = __________________ # n
0 = __________________________
Au _____________________
_______________________
197
79
__________________
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Example: Determine the number of p+, e
-, and n
0 of each atom.
14C p
+ ____________________
7Li p
+ ____________________
e- ____________________ e
- ____________________
n0 ____________________ n
0 ____________________
Example: Identify each atom:
16 X _____________________________
108 X _____________________________
Remember……atoms are, “ ________________________ _____________________.” Can they ever have a charge?
YES!! They can become __________! What is an ion?
an atom or group of atoms that has a (____) or (____) charge. How are ions formed?
when ______ are ___________________ between atoms Remember there are two types of ions: 1. Cations: (______) charged
formed by ______________ 1 or more ______________
lose (____) charge = become more (____)
______________ lose e- to form ___________
2. Anions: (______) charged
formed by __________________ 1 or more ________________
gain (_____) charge = become more (_____)
______________ gain e- to form ____________
6 6
8
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Example: Complete the following table.
Symbol
# p
+
# n
0
#e
-
e
- change
54Fe
+3 23
38 50 lose 2
6 8 6
Example: Complete the following table.
Symbol
electron change
formula of ion
cation or anion?
Na loses 1 e-
Cl gains 1 e-
Ca+2
S-2
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Counting Subatomic Particles
1. What is the distinction between atomic number and mass number? Between mass number and
atomic mass? ____________________________________________________________________________
_________________________________________________________________________________________ 2. Give the number of protons and neutrons in the nucleus of each of the following atoms:
a. 238 p+
___________ e. 52 p+ ___________
Pu Cr 94 n0 _______ 24 n0 _______
b. copper—65 p+ ___________ f. helium—4 p+
___________
n0 _______ n0 _______
c. 15 p+ ___________ g. 207 p+
___________ N Pb n0 _______ n0 _______
d. 3 p+ ___________ h. 151 p+
___________ H Eu n0 _______ n0 _______ 3. Identify each of the following elements: a. 31 b. 39 c. 127 d. 173 X __________ X ___________ X _____________ X ____________ 15 19 53 70 4. How many protons, neutrons, and electrons are in each of the following atoms or ions? a. p+ _______ c. p+ _______ e. p+ ______ g. p+ ______
Mg n0 _______ S-2 n0 _______ Co+3 n0 ______ Al+3 n0 ______
e- _______ e- _______ e- ______ e_ ______
b. p+ _______ d. p+ _______ f. p+ ______ h. p+ ______
Mg+2 n0 _______ F-1 n0 _______ Co+2 n0 ______ Ne n0 ______
e- _______ e- _______ e- ______ e- _______
5. Complete the following chart.
Symbol
# protons # neutrons # electrons electron charge
33 42 lose 3
128Te-2
54
16 16 16
81 123 lose 1
195Pt
24
12
24
12
33
16
19
59
27
59
27
27
20
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Who Am I?
Practice Quiz
A. Thomson B. Rutherford C. Millikan D. Democritus E. Dalton
1. Billiard Ball Model _______
2. Discovered the electron _______
3. Gold Foil Experiment _______
4. Nuclear Model _______
5. 400 B.C. _______
6. Transformed Democritus’ ideas into scientific theory based on experimentation _______
7. Atom is an indivisible sphere of solid material throughout _______
8. First recorded person to observe and think about the atom _______
9. His theory could not explain what held atoms together in a compound _______
10. Studied cathode rays _______
11. Oil Drop Experiment _______
12. Calculated the numerical charge on an electron _______
13. Discovered the nucleus _______
14. Plum Pudding Model _______
15. Proposed the atom to be positive material with negative particles embedded in it _______
Label each picture with the appropriate scientist and model name.
_____________________ ______________________ ______________________ _____________________ ______________________ ______________________
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Atomic Mass & Isotopes
Atomic mass
a ___________________ _________________ mass of the atoms in a naturally
occurring _______________ of an element
is NOT a _______________ number
a weighted average that takes into account both the _________ and relative
_________________ of all the existing _________________.
What is an isotope?
atoms of an element that are ______________ alike but differ in the number
of ________________.
What does this change in the atom?
__________________________________________________________________
Are their atomic numbers the same?
__________________________________________________________________
Isotope Example: OXYGEN
p+
e-
n0 relative atomic
mass
oxygen – 16 15.995 amu
oxygen – 17 16.995 amu
oxygen - 18 17.999 amu
Isotopes
HOW ARE THEY DIFFERENT??
___________________________________
___________________________________
___________________________________
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Atomic Mass:
The unit for atomic mass is called the __________ _________ _______ (amu)
1 amu = exactly 1/12 the mass of a ____________-12 atom
1 amu =
How is atomic mass, or the weighted
average calculated?
atomic = ∑ (mass x relative abundance) mass
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Isotope Example The element silicon has three naturally occurring isotopes. Use the following information to calculate the average atomic mass for silicon. Report the answer to 4 sig figs.
SILICON
Isotope Relative Atomic Mass (amu) % abundance relative abundance 28
Si 27.976926533 92.2297 29
Si 28.97649472 4.6832 30
Si 29.9737022 3.0872
Isotope Example The element nitrogen has two naturally occurring isotopes. The isotope with a mass of 14.00307 amu occurs 99.632% of the time. If the average atomic mass of nitrogen is 14.01 amu, what is the mass of the other isotope? Report the answer to 4 sig figs.
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Isotopes
1. Two isotopes of oxygen are oxygen-16 and oxygen-18. Write the chemical symbol for each isotope.
2. Using the periodic table, determine the number of neutrons in these atoms. a. 12C ___________ b. 15N ___________ c. 226Ra ___________ d. 264Bh ___________ 3. Explain why the atomic masses of most elements are not whole numbers. 4. How are the three isotopes of hydrogen alike? How are they different? 5. The element lead has 4 naturally occurring isotopes. Use the following information to
calculate the average atomic mass for lead. Report the answer to 4 sig figs.
Isotope Relative Atomic Mass (amu) % abundance relative abundance 204Pb 203.973020 1.4 206Pb 205.974440 24.1
207Pb 206.975872 22.1 208Pb 207.976627 52.4
6. The element boron has two naturally occurring isotopes. The isotope with a mass of 10.012
amu occurs 19.91% of the time. What is the mass of the other isotope? The average atomic mass of boron is 10.811 amu. Report your answer to 3 sig figs.
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History and Atomic Structure Review 1. Write at least three statements to describe the scientific works of these historical men.
a. Democritus
____________________________________________________________________
____________________________________________________________________
____________________________________________________________________
____________________________________________________________________
b. Dalton
____________________________________________________________________
____________________________________________________________________
____________________________________________________________________
____________________________________________________________________
c. Thomson
____________________________________________________________________
____________________________________________________________________
____________________________________________________________________
____________________________________________________________________
d. Millikan
____________________________________________________________________
___________________________________________________________________
____________________________________________________________________
e. Rutherford
____________________________________________________________________
____________________________________________________________________
____________________________________________________________________
____________________________________________________________________
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2. List three differences between isotopes of the same element.
a. ________________________________________________________
b. ________________________________________________________
c. ________________________________________________________
3. Oxygen and hydrogen react to form water through the following reaction:
2H2 + O2 2H2O In one reaction, 4 grams of hydrogen combines with oxygen to form 36 grams of water. How much oxygen was used? (HINT: Remember Lavoisier and the Law of Conservation of Mass)
4. Iron has three isotopes with the following abundances: 54Fe (5.8%), 56Fe (91.7%), 57Fe (2.5%).
a. Without doing any math, what do you expect the average atomic mass of iron to be? Why?
b. Use the following information to calculate the average atomic mass of iron. Compare your answer to the assumption you made in letter a.
Isotope Relative atomic mass (amu) % Abundance 54Fe 53.9396105 5.8% 56Fe 55.9349375 91.7% 57Fe 56.9353940 2.5%
5. Provide the missing information for the isotope, 88Sr
a. Atomic number ________ d. Number of protons ________
b. Number of neutrons ________ e. Number of electrons ________
c. Mass number ________ f. Net charge ________
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6. Identify the following elements. Write the symbol and name:
a. 39X ____________ ___________________________
b. 56X ____________ ___________________________
c. 79X ____________ ___________________________ 7. Supply the missing information:
27Al+3 Ra-226 127I- 31P-3 Cr-52 Li-7 115In+3 133Cs+ 40Ca
# e- _____ _______ _______ _______ ______ _______ _______ _______ _______ # p+
_____
_______
_______
_______
_______
_______
_______
_______
_______
# n0
_____
_______
_______
_______
_______
_______
_______
_______
_______
8. Supply the missing information.
Isotope Symbol Z Mass # # p+ # n0 # e- a. hydrogen-2
2H
__________
__________
__________
__________
__________ b. _______________
24Mg
__________
__________
__________
__________
__________ c. _______________
_______
__________
__________
31
39
28
d. _______________
81Br-1
__________
__________
__________
__________
__________ e. _______________
_______
__________
201
80
__________
__________
9. True or false.
a. Dalton believed in subatomic particles. _______ b. On the periodic table, elements are arranged in order of increasing atomic mass. _______ c. An atomic mass unit is defined as 1/12 the mass of a carbon-12 atom. _______ d. Electrons and neutrons are found in the nucleus of an atom. _______ e. A vertical column of elements on the periodic table is called a group. _______ f. The proton and electron have similar masses. _______
19
26
35
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10. Supply the missing information. Symbol of element Change in electrons Formula of Ion Cation or Anion? a. Ba
loses 2 e-
____________________
___________________
b. Li
__________________
Li+
____________________
c. P
gains 3 e-
____________________
____________________
d. Se
____________________
Se-2
____________________
11. Consider the data: Ga+3, K+, Se-2, Ca+2, Sn+2, P-3, I-
a. According to the data, there is pattern in how metals and nonmetals form ions. What is the pattern?
12. What is the difference between an atom and an ion? _______________________________________
__________________________________________________________________________________
13. Give the correct symbol or name for the following elements.
a. calcium ___________ h. sodium ___________ b. cadmium ___________ i. F __________________
c. Fe ______________________ j. lead ___________
d. antimony ___________ k. Cs ___________________
e. potassium ___________ l. arsenic ___________
f. P ______________________ m. silver ___________
g. S ______________________ n. gold ___________
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History and Subatomic Particle Review: Take Two DIRECTIONS: Answer the following questions using complete sentences where needed. 1. Compare and contrast Thomson’s plum pudding atomic model with Rutherford’s nuclear atomic
model. ___________________________________________________________________________________________________________________________________ ___________________________________________________________________________________________________________________________________ ___________________________________________________________________________________________________________________________________
2. Which subatomic particle was discovered by researchers working with a cathode ray tube?
___________________________________________________________________________________________________________________________________
3. Which statement is consistent with the results of Rutherford’s gold foil experiment? a. All atoms have a positive charge b. Atoms are mostly empty space c. The nucleus of an atom contains protons and electrons. d. Mass is spread uniformly throughout the atom.
4. Describe the structure of a typical atom. Identify where each subatomic particle is located.
___________________________________________________________________________________________________________________________________ ___________________________________________________________________________________________________________________________________ ___________________________________________________________________________________________________________________________________
5. Which subatomic particles are charged? ______________________________________________________________________ 6. Which subatomic particle identifies an atom as that of a particular element? How is this particle
related to the atom’s atomic number? ___________________________________________________________________________________________________________________________________ ___________________________________________________________________________________________________________________________________ ___________________________________________________________________________________________________________________________________
7. How does the mass of a neutron compare to that of a proton? An electron? ___________________________________________________________________________________________________________________________________ ___________________________________________________________________________________________________________________________________
8. Which subatomic particles account for most of the atom’s mass? ___________________________________
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9. How are isotopes of the same element alike? How are they different? ___________________________________________________________________________________________________________________________________ ___________________________________________________________________________________________________________________________________ ___________________________________________________________________________________________________________________________________
10. Nitrogen has two naturally occurring isotopes, N-14 and N-15. The atomic mass of nitrogen is
14.007 amu. Which isotope is more abundant in nature? Explain your answer. ___________________________________________________________________________________________________________________________________ ___________________________________________________________________________________________________________________________________ ___________________________________________________________________________________________________________________________________
11. Use the data from the four isotopes below to calculate the transition metal’s average atomic
mass. Then, identify the element. (Show your work). 49.946 amu (4.35%) 51. 941 amu (83.79%) 52.941 amu (9.50%) 53.939 amu (2.36%)
12. 67.26 g of mercury (II) oxide, a red powder, is heated to produce 62.28 grams of mercury, a silver
liquid. In this process, oxygen gas is also produced. According to the Law of Conservation of Mass, how many grams of oxygen gas are produced when this sample is heated?
13. How can one calculate the number of neutrons in the nucleus of an atom?
___________________________________________________________________________________________________________________________________
14. What is the net charge on an element that has 55 p+, 78 n0, and 54 e-? ____________________________ 15. What could be calculated by combining Thomson’s work with Millikan’s experiment?
___________________________________________________________________________________________________________________________________
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DIRECTIONS: Complete the following chart.
Name of Element
Symbol of Element
Atomic Number
Mass Number
Number of Protons
Number of Neutrons
Number of Electrons
Copper 29 35 29 Tin 69 50
I 53 127 Uranium 238 92
K 19 20 Lithium 7 3
O 8 8 Gold 79 197
32 16 Silver 47 108
Chromium 28 24 Co 59 32 27 Ni 28 30
Zinc 30 35 Al 14 13 Hg 80 201
Platinum 195 Fe 56 30 H 1 1 He 2 4 9 4 4 Mg 12 12 12 C 6 6
Silicon 14 14 Cl 17 18 Bi 209 83
Boron 5 11 Ca 20 20 20 55 25
Lead 207 82 Sodium 23 Fluorine 9 10 9
P 15 31
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Name ____________________________________________________ Period ___________________
ATOMIC STRUCTURE - Vocabulary Review Match the correct vocabulary term to each numbered statement. Write the letter of the correct term on the line. Each answer can only be used once. a. isotope f. indivisible k. mass number
b. proton g. neutron l. gold foil
c. atomic number h. cation m. atom
d. nucleus i. anion n. atomic mass
e. oil drop j. atomic mass unit o. electron ___________ 1. Defined as 1/12 the mass of a carbon-12 atom.
___________ 2. A negatively charged subatomic particle.
___________ 3. The number of protons in the nucleus of an atom of an element.
___________ 4. Millikan’s famous experiment.
___________ 5. A negatively charged ion form by gaining one or more electrons.
___________ 6. The smallest particle of an element that retains its identity in a chemical
reaction.
___________ 7. The meaning of the Greek work, “atomos.”
___________ 8. Rutherford’s famous experiment.
___________ 9. The total number of protons and neutrons in an atom.
__________10. A positively charged subatomic particle that is found in the nucleus of an atom.
__________11. A weighted average mass of all the atoms in a naturally occurring sample of
an element.
__________12. The tiny, dense central portion of an atom, composed of protons and
neutrons.
__________13. A subatomic particle with no charge and is found in the nucleus of an atom.
__________14. A positively charged ion formed by the loss of one or more electrons.
__________15. Atoms of an element that are chemically alike but differ in the number of
neutrons.
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Name_____________________________________________________ Period ______________
IT’S WHAT’S ON THE INSIDE THAT COUNTS Improve your understanding of subatomic particles and the structure of the atom while you work to reveal a letter very important to atomic structure. _______________________ 1. The number of protons in the element with atomic number 23.
_______________________ 2. The number of electrons in hydrogen—3.
_______________________ 3. The number of neutrons in boron—11.
_______________________ 4. The total number of subatomic particles in 15
N.
_______________________ 5. The number of electrons in a phosphorus atom.
_______________________ 6. The mass number of uranium—238.
_______________________ 7. The atomic number of 26
Mg.
_______________________ 8. For deuterium, 2H, A = ?
_______________________ 9. The number of neutrons in the most common isotope of fluorine.
_______________________ 10. The number of electrons in the most common isotope of
chromium.
_______________________ 11. The total number of subatomic particles in the most common
isotope of Sc.
_______________________ 12. The number of neutrons in 234
U.
_______________________ 13. The number of neutrons in copper—65.
_______________________ 14. The total number of subatomic particles in the most common
form of carbon.
_______________________ 15. The value of Z for 17
O.
_______________________ 16. The value of Z for cesium.
_______________________ 17. The value of A for carbon—14.
_______________________ 18. The value of (A - Z) for magnesium—28.
_______________________ 19. The atomic number for calcium.
_______________________ 20. The value of Z for bismuth.
_______________________ 21. The number of electrons in a gold atom.
_______________________ 22. The number of electrons in a scandium atom.
_______________________ 23. The atomic number of manganese.
_______________________ 24. The mass number for iodine—127.
_______________________ 25. The total number of subatomic particles in 80
Br.
_______________________ 26. The number of electrons in a tin atom.
30
IT’S WHAT’S ON THE INSIDE THAT COUNTS For each clue, shade in the box below that contains the answer to the clues found on the front of this paper. When complete, connect the unshaded boxes with one continuous line.
The letter _______________, which means __________________________.
1 23 12 142 83 24
19 22 71 288 44 8
2 18 10 58 16 79
66 20 99 127 55 14
40 25 86 106 15 212
50 21 36 115 6 238
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Turning Copper Into Gold A study of Alloys
DISCUSSION: In the early history of chemistry, the alchemists dreamed of being able to change cheap metals into precious ones by simply adding or subtracting elements in the proper proportions. For example, lead might be turned into gold by adding the right amount of mercury (the element they thought imparted metallic properties to substances). This search for the proper technique of changing “base metals” into gold lasted for centuries. During the search, the alchemists discovered mineral acids — hydrochloric, nitric, and sulfuric — and phosphorus, which were far more important to the world of science than the creation of gold. However, they could not be deterred from the main quest, and some became so unscrupulous at their craft that they brought the profession into such disrepute that the word “alchemy” had to be abandoned. By the seventeenth century, alchemy graduated to a more sophisticated science called “chemistry,” and alchemists were called “chemists.” Today we know that this process of changing one metal into another is impossible through ordinary chemical means, and can only be accomplished by a nuclear reaction in which the number of protons in an atom’s nucleus is altered in some way. Since an atom’s identity is determined by the number of protons in the nucleus, changing this will change the identity of the element. The transuranium elements (elements beyond uranium) are all man-made by bombarding the nucleus of another element. In this experiment we will produce an alloy, and in the process, create the illusion of changing copper into gold. An alloy, a solid solution of two or more metals, is usually produced by solidification of its molten parts; this is the method used in this experiment. MATERIALS a penny zinc dust 6M HCl 3M NaOH Bunsen burner beakers crucible tongs watch glass wood splint iron ring stand apparatus PROCEDURE: 1. Obtain a penny, preferably fairly clean and
shiny. 2. Clean the penny with a piece of steel wool until
it resembles a shiny new penny.
3. Weigh about 1.5 grams of zinc dust in a 250-mL beaker that has been placed on a balance and tared.
4. Pour 50 mL of 3M NaOH into the beaker containing the zinc dust.
5. Heat the Zn and NaOH solution until it is hot but not boiling.
6. Submerge the shiny, clean penny in a hot solution of zinc dust and 3.0 M NaOH for at least one minute or until both sides are completely coated with zinc (make sure no copper is showing).
7. After the penny is thoroughly coated with zinc on both sides, remove it from the solution with your crucible tongs. Rinse thoroughly with tap water to remove any excess zinc.
8. After the penny has been rinsed, hold it with your fingertips under running water and rub any large clumps of zinc off the penny. (NOTE: If you leave any loose zinc on your penny, it will not turn into a nice shiny gold penny.)
9. After all the loose grains of zinc have been washed off, dry the penny with a SMALL PIECE of paper towel, removing any clumps of zinc that may have adhered to the penny. It should look like a nickel. When you are finished polishing your penny, place this paper towel in a container located in the fume hood. DO NOT PLACE THIS PAPER TOWEL IN THE WASTE CAN!!!
10. Hold the penny by its edges with crucible tongs. Place it into the flame of a Bunsen burner. When you detect a change in color (toward a shade of bronze), flip the coin over and heat it for two to three more seconds.
11. Quickly remove the penny from the flame and plunge it into a beaker of cold water. You should now be the owner of a “gold” medallion.
12. Decant the NaOH solution from the leftover zinc in your beaker.
13. Pour 20 mL of HCl acid into the beaker containing the zinc. Cover with a watch glass.
14. After the reaction has proceeded for one minute, place a flaming splint in the beaker to determine what gas is given off in the reaction.
15. Clean your equipment and return to the cabinets; wipe your lab station.
The Alchemist’s Dream
32
Name __________________________________________________________ Period _____________
The Alchemists’ Dream
CONCLUSION: Answer the following questions, legibly and neatly, in full sentences in the spaces provided below. 1. Who were the alchemists and what did they claim to do? 2. How does the penny turn silver? 3. Why did the penny need to be heated in order to turn “gold”? 4. Does the formation of the “gold” represent the formation of an element, a compound, or
mixture? Explain your answer. 5. What gas is produced from the reaction of Zn and HCl? How do you know? MATCH THE FOLLOWING ALLOYS WITH THEIR CHEMICAL COMPOSITION. _____ 6. bronze a. iron, carbon, and manganese _____ 7. sterling silver b. copper and tin _____ 8. white gold c. bismuth, tin, lead, and cadmium _____ 9. yellow gold d. tin, antimony, and copper _____ 10. pewter e. gold and platinum _____ 11. steel f. copper and zinc _____ 12. brass g. gold and copper _____ 13. Wood’s metal h. silver and copper
14. From the choices above, what is the name of the alloy that formed on your penny? _______
33
Investigating Average Atomic Mass
INTRODUCTION:
The mass of a single oxygen-16 atom is
2.657 x 10-23 grams. Since this is an
extremely small mass, it would be very
impractical to mass individual atoms.
Instead, atoms are assigned relative masses
using carbon-12 as the standard.
The concept of relative mass is based on
the comparison of one substance to another
that is accepted as the standard. On the
atomic scale, all atoms are compared to the
carbon-12 isotope. An atomic mass unit
(amu) is defined as exactly one-twelfth the
mass of a carbon-12 atom.
In nature, most elements are found as a
mixture of two or more isotopes. For
example, copper consists of 69.17 percent
copper-63 and 30.83 percent copper-65.
Copper-63 has a relative atomic mass of
62.94 amu and copper-65 has a relative
mass of 64.93 amu. To find the average
relative atomic mass (the mass that appears
on the periodic table), multiply the
abundance of each isotope by its relative
mass tive mass and then add the results:
0.6917 x 62.94 amu + 0.3083 x 64.93 amu
= 63.55 amu
OBJECTIVE: To analyze the isotopes of “candium” and to calculate its average atomic mass. PROCEDURE: 1. Obtain a sample of the element
“candium.” 2. Treat each color as an isotope of the
element. Separate the isotopes into groups by color.
3. Count the number of atoms in each sample; record in the data table.
4. Put the cup on the balance; tare. Place each isotope in the cup and measure its mass; record in the data table.
5. You may now eat your candium atoms.
Candium Atoms
34
35
Name ___________________________________________________________ Period _____________
Candium Calculations and Questions
DIRECTIONS: Perform the following calculations for each isotope, pay attention to significant figures. Record your answers in the data table. You do not have to show your work for numbers 1 – 3.
1. Calculate the mass of an individual isotope atom by dividing the total mass of the isotope by the number of particles of that isotope.
2. Calculate the relative abundance of each isotope by dividing its number of particles by the
total number of particles. 3. Calculate the percent abundance of each isotope by multiplying the relative abundance by
100. (report your answer to 3 significant figures) 4. Calculate the average atomic mass of candium. (Hint: use the “mass of isotope” data in your
calculation) SHOW YOUR WORK!!! This is the number that would appear on the periodic table for candium. (report your answer to three significant figures)
ANSWER: ____________________
Red
Blue
Yellow
Green
Orange
Brown
Number
Total Mass (g)
Mass of Isotope (g)
Relative Abundance
Percent Abundance
36
1. Determine the average atomic mass of a magnesium atom: 78.99 % of the atoms have a relative mass of 23.985amu, 10.00 % have a relative mass of 24.986 amu and 11.01 % of the atoms have a relative mass of 25.982 amu. Record your answer to 5 significant figures.
2. The element silver has two naturally occurring isotopes. The isotope with a mass of 106.905
amu occurs 51.82 % of the time. If the average atomic mass of silver is 107.868 amu, what is the mass of the other isotope? Record your answer to 5 significant figures.
3. BONUS: The element europium exists in nature as two naturally occurring isotopes: one has
a mass of 150.9196 amu and the other has a mass of 153.9209 amu. The average atomic mass of europium is 151.96 amu. Calculate the percent abundance of the two isotopes. Record your answers to 5 significant figures.
37
WHAT dO I need to know?? Unit 4: History & Structure of the Atom
multiple choice, Matching & True/false
o Atomic number – definition o Mass number – definition o Subatomic Particles
Definitions Mass of each compared to
one another Counting e-, p+, n0 Where are the subatomic particles
located? Which subatomic particle is involved in
chemical reactions? Protons vs. electrons (mass, size, charge,
etc.)
o Isotopes Definition How do isotopes of the same element
differ? How are they alike? Solve problem for atomic mass
o Law of conservation of mass (#3 on review
sheet)
38
o Periodic Table Where are the metals, nonmetals,
metalloids? Elements and their symbols Groups vs. periods Names of groups (i.e. alkali metals,
alkaline metals, etc.)
o Historical Men (#1 on review sheet) Dalton Democritus Thomson Rutherford Millikan Their experiments
o Review: Chemistry is a subject that builds
upon prior knowledge. You are responsible for general concepts that have been covered on previous tests.