UNIT: ATOMIC STRUCTURE

ESSENTIAL QUESTIONS: HOW DID THE CONCEPT OF THE ATOM CHANGE OVER TIME?WHAT COMPONENTS MAKE UP AN ATOM?HOW ARE ATOMS OF ONE ELEMENT DIFFERENT FROM ATOMS OF ANOTHER ELEMENT?

CCLS:RST 1,2,3,4,7,8,9WHST 1A,1B,1C,1D,1E, 2A,2B,2C,2D,2E, 4,5,6,7,8,9,10

Aim: How can there be different varieties of atoms?Do now: What are the subatomic particles and their respective charges?

PROPERTIES OF SUBATOMIC PARTICLES

Particle

Symbol

Location Relative charge

Relative mass (mass of proton = 1 amu)

Actual mass (g)

Electron -1

Proton +1

Neutron 0

PROPERTIES OF SUBATOMIC PARTICLES

Particle

Symbol

Location Relative charge

Relative mass (mass of proton = 1 amu)

Actual mass (g)

Electron e- Outside the nucleus

-1 1/1840 9.11 x 10-

28

Proton p+ In the nucleus +1 1 1.67 x 10-

24

Neutron n0 In the nucleus 0 1 1.67 x 10-

24

ATOMS OF ELEMENTS

So if every atom has protons, neutrons, and electrons, what makes one element different from another?

Look at your Periodic Table. What numbers are different from element to element?

How might we identify an element, besides from its name and/or symbol? Atomic Number

ATOMIC NUMBER

If a atom of Argon has: An atomic number of 18 An atomic mass of 40 18 protons 18 electrons 22 neutrons

What is the relationship between atomic number and the subatomic particles? An element’s atomic number is the number of

protons and number of electrons in an atom of that element.

Atomic # = # p+ = # e-

ATOMIC MASS NUMBER

If a atom of Argon has: An atomic number of 18 An atomic mass of 40 18 protons 18 electrons 22 neutrons

What is the relationship between atomic mass and the subatomic particles? An element’s atomic mass number is the number of

protons and neutrons in the nucleus of an atom of that element.

Atomic mass # = # p+ + # n0

ATOMIC MASS NUMBER

If all atoms are comprised of protons, neutrons, and electrons, why aren’t electrons counted in the atomic mass?

The relative mass of an electron is so small that its mass is considered negligible.

Particle

Symbol

Location Relative charge

Relative mass (mass of proton = 1 amu)

Actual mass (g)

Electron e- Outside the nucleus

-1 1/1840 9.11 x 10-

28

Proton p+ In the nucleus +1 1 1.67 x 10-

24

Neutron n0 In the nucleus 0 1 1.67 x 10-

24

NEUTRAL ATOMS

All atoms are neutral!! If an atom of Argon has an atomic number of

18 How many protons does it have?

18 protons What is the charge of each proton?

+1 What particle has the opposite charge?

Electrons, -1 How many electrons are needed to make this

atom neutral? 18 electrons

ATOMIC NUMBER & ATOMIC MASS NUMBER

Elements are identified by their atomic number.

An element’s atomic number is the number of protons and electrons in an atom of that element. Atomic # = # p+ = # e-

Elements are different because they contain different numbers of protons.

An element’s atomic mass number is the number of protons and neutrons in the nucleus of an atom of that element. Atomic mass # = # p+ + # n0

ATOMS OF THE FIRST TEN ELEMENTS

Name Symbol

Atomic number

Protons

Neutrons

Mass number

Electrons

Hydrogen H 1 1 0 1 1

Helium 4

Lithium 7

Beryllium 9

Boron 11

Carbon 12

Nitrogen 14

Oxygen 16

Fluorine 19

Neon 20

ATOMS OF THE FIRST TEN ELEMENTS

Name Symbol Atomic number

Protons

Neutrons

Mass number

Electrons

Hydrogen H 1 1 0 1 1

Helium He 2 2 2 4 2

Lithium Li 3 3 4 7 3

Beryllium Be 4 4 5 9 4

Boron B 5 5 6 11 5

Carbon C 6 6 6 12 6

Nitrogen N 7 7 7 14 7

Oxygen O 8 8 8 16 8

Fluorine F 9 9 10 19 9

Neon Ne 10 10 10 20 10

DISPROVING DALTON’S ATOMIC THEORY

How do our calculations help disprove Dalton’s atomic theory?

The atom is not the smallest particle; there are subatomic particles

Atoms of different elements may have similarities Boron and Carbon can have the same number of

neutrons Fluorine and Neon can have the same number of

neutrons

BOHR’S MODEL

Describe what Bohr’s model of the atom looks like. Protons and neutrons are in the nucleus Electrons surround the nucleus

BOHR’S MODEL OF A SODIUM ATOM

Sodium, Na Atomic Mass: 23 Atomic Number: #p+: #n0: #e-: What is its electron configuration?

What is its shorthand notation?

11 p+

12 n0 182

11

12

11

11

2-8-1

2311Na

ELECTRON CONFIGURATION OF EXCITED STATE What does it mean when an atom goes into excited state?

In ground state, Na has an electron configuration of 2-8-1

During excited state, any one electron can move to a higher energy level as long as there is room. The total number of electrons remains the same.

What are some possible electron configurations for an atom of Na in its excited state? 2-7-2 1-8-2 2-8-0-1

ASSIGNMENT

For your assigned atom:1. Indicate the #protons, #electrons, and

#neutrons2. Write the shorthand notation for the atom3. Indicate the electron configuration in ground

state4. Draw the Bohr’s model for this neutral atom in

ground state5. Indicate one possible electron configuration for

excited state

Find the person(s) with the same element. On a piece of looseleaf, attach your drawings

& create a t-chart of similarities and differences.

ISOTOPES

What you and your partner(s) have are called isotopes.

Based on your comparison, define isotopes.

Isotopes are atoms of the same element that have different mass numbers. Same number of protons (because they are the

same element) Different number of neutrons (remember that

atomic mass = # protons + # neutrons)

UNIT: ATOMIC STRUCTURE

ESSENTIAL QUESTIONS: HOW DID THE CONCEPT OF THE ATOM CHANGE OVER TIME?WHAT COMPONENTS MAKE UP AN ATOM?HOW ARE ATOMS OF ONE ELEMENT DIFFERENT FROM ATOMS OF ANOTHER ELEMENT?

CCLS:RST 1,2,3,4,7,8,9WHST 1A,1B,1C,1D,1E, 2A,2B,2C,2D,2E, 4,5,6,7,8,9,10

Aim: Why are the atomic masses on the Periodic Table different from the isotope masses?Do now: How many protons, neutrons, and electrons are in Magnesium-24?

MAGNESISUM-24

*REMINDER* The 2 equations you need are: Atomic # = #p+ = #e-

Atomic mass = #p+ + #n0

Atomic mass – Atomic number – # protons – # neutrons – # electrons –

1212

12

12

24

IONS

Ions are electrically charged atoms They become electrically charged because

they have gained or lost electrons

Magnesium ion, Mg+2

Look for it on your Periodic Table. What is another name for the ionic charge?

The atom is no longer neutral.

Let’s calculate the number of protons and electrons…

That’s the charge!

Oxidation State

CHARGED ATOMS – IONS

If an ion of Magnesium has a charge of +2… How many protons does it have? What is the charge of each proton? What particle has the opposite charge? How many electrons are needed to make this

atom have a +2 charge?

# Particles Charge Net Charge

TOTAL = +2

12 protons +1 +12

? electrons -1 -1010 electrons

YOU TRY! How many protons & electrons are in Si-4?

What is the net charge of an ion with 8 protons and 10 electrons? (What element is this?)

# Particles Charge Net Charge

TOTAL = -4

14 protons +1 +14

-18-118 electrons

# Particles Charge Net Charge

TOTAL = -2

8 protons +1 +8

-10-110 electrons

This is O-2

WEIGHTED ATOMIC MASS

According to your Periodic Table, what is the atomic mass of hydrogen? 1.00794 amu (atomic mass units)

If the three isotopes of hydrogen have different atomic masses, where do we derive 1.00794 amu?

WEIGHTED AVERAGES

In a Chemistry class:

Which category would have the greatest effect on your overall?

How would you calculate your overall grade?

Your Chemistry Class Weight and Grade

% Weight Category Your Average

60% Exams 85

20% Homework 94

20% Lab 78

WEIGHTED AVERAGES

Because 60% of your grade is comprised of your exam scores, the 85% you received in that category affects your grade the most.

Your overall grade is closest to the score you received in the exam category.

Your Chemistry Class Weight and Grade

% Weight Category Your Average Weighted Average

60% Exams 85 0.60 x 85 = 51

20% Homework 94 0.20 x 94 = 18.8

20% Lab 78 0.20 x 78 = 15.6

Overall Weighted Average (Overall Grade) = 51 + 18.8 +15.6 = 85.4%

WEIGHTED ATOMIC MASS

Atomic masses are calculated in the same fashion.

Which isotope has the highest percent abundance?

What mass number will the weighted atomic mass be closest to?

Isotopes of Hydrogen

Natural percent

abundance

Isotope Mass (amu)

Weighted Average

99.985% Hydrogen-1

1.0078 % abundance x isotope mass

0.015% Hydrogen-2

2.0141 % abundance x isotope mass

Negligible Hydrogen-3

3.0160 % abundance x isotope mass

CHECK YOURSELF Is the calculated weighted average atomic

mass close to what we see on the Periodic Table?

Is the calculated weighted average atomic mass closest to the isotope with highest percent abundance?

Isotopes of Hydrogen

Natural percent

abundance

Isotope Mass (amu)

Weighted Average

99.985% Hydrogen-1

1.0078 0.99985 x 1.0078 = 1.0076

0.015% Hydrogen-2

2.0141 0.00015 x 2.0141 = 0.0003

Negligible Hydrogen-3

3.0160 0

Overall Weighted Average = 1.0076 + 0.0003 + 0 = 1.0079 amu

PRACTICE Calculate the average atomic mass for O and

N. Isotopes of Oxygen

Natural % abundanc

e

Isotope Mass (amu)

Weighted Average

99.759% Oxygen-16 15.995

0. 037% Oxygen-17 16.995

0.204% Oxygen-18 17.999

Isotopes of Nitrogen

Natural % abundanc

e

Isotope Mass (amu)

Weighted Average

99.63% Nitrogen-14

14.003

0.37% Nitrogen-15

15.000

PRACTICE Calculate the average atomic mass for O and

N. Isotopes of Oxygen

Natural % abundanc

e

Isotope Mass (amu)

Weighted Average

99.759% Oxygen-16 15.995 0.99759 x 15.995 = 15.956

0.037% Oxygen-17 16.995 0.00037 x 16.995 = 0.006

0.204% Oxygen-18 17.999 0.00204 x 17.999 = 0.037

Average Atomic Mass = 15.956 + 0.006 + 0.037 = 15.999 amuIsotopes of Nitrogen

Natural % abundanc

e

Isotope Mass (amu)

Weighted Average

99.63% Nitrogen-14

14.003 0.9963 x 14.003 = 13.951

0.37% Nitrogen-15

15.000 0.0037 x 15.000 = 0.056

Average Atomic Mass = 13.951 + 0.056 = 14.007 amu