matter & the atom. anything that takes up space and has mass can be classified as solid, liquid,...
TRANSCRIPT
Matter & The Atom
Anything that takes up space and has mass
Can be classified as solid, liquid, gas or plasma
Matter
Is it matter?
What is not matter?
ENERGY, HEAT, LIGHT, ELECTROMAGNETIC WAVES, MAGNETIC FIELDS, IDEAS, ETC.
Properties of MatterDescribe the characteristics and behavior
of matter, including the changes that matter undergoes
Observing Matter Macroscopic Observations: Observations made with the
5 senses
Microscopic Observations: Observations made with a microscope
Submicroscopic Observations: Observations of substances so small they cannot even be seen with a microscope
Macroscopic Microscopic Submicroscopic
Qualitative Observation: Describes the properties of a substance
Quantitative Observation: An observation that involves a numerical value.
Physical Properties
What are the physical properties represented in the image above?
chara
cteris
tic
s
quantitative
qualitative
Chemical Properties
MIXTURESTwo or more elements physically combined.
How can you tell something is a mixture?It can be physically separated into its parts.
Heterogeneous Mixtures
• The prefix “hetero” means “different”• A mixture with different compositions throughout• You can see each phase (part) of the mixture
Homogeneous Mixtures
• The prefix “homo-” means “the same”
• A mixture that is the same throughout
• You cannot see the phases (parts) of the mixture.
HETEROGENEOUS OR
HOMOGENEOUS?
Solutions• Solute: The substance being dissolved in a
solution• Solvent: The substance that dissolves the solute• Aqueous Solution: A solution in which water is
the solvent
What is the solute?What is the solvent?
82% Fe
18% Cr
ALLOY
NAME OF ALLOY % MAKE UP EXAMPLE
Stainless Steel 73-79% Fe14-18% Cr7-9% Ni
Sterling Silver 92.5% Ag7.5% Cu
18-karat white gold 75% Au12.5% Ag12.5% Cu
14 karat gold 58% Au14-28% Ag14-28% Cu
Methods to Separate Mixtures
• Filtration: Separates a solid from a liquid
Separating…
• Magnet: Separates Fe, Co, or Ni
Separating…• Distillation: Separates two or more liquids
with different boiling points.
Separating…• Crystallization: Separates crystalline solids
from a saturated liquid
Separating…
• Chromatography: Separates different types of liquids
PURE SUBSTANCEPURE SUBSTANCE Matter with the same fixed Matter with the same fixed
composition and propertiescomposition and properties– First Type of Pure SubstanceFirst Type of Pure Substance
ElementElement– The Periodic Table:The Periodic Table: A chart that lists the chemical A chart that lists the chemical
name and chemical symbol for each elementname and chemical symbol for each element– Chemical Symbol:Chemical Symbol: A shorthand abbreviation for A shorthand abbreviation for
the name of an elementthe name of an element– You can tell a substance is an element because it You can tell a substance is an element because it
is on the periodic tableis on the periodic table
-Can you separate an element? No-Can you separate an element? No
Aluminum = ___ Aluminum = ___ Gold = ____ Gold = ____ Tin = ____ Tin = ____
PURE SUBSTANCEPURE SUBSTANCE Matter with the same fixed composition and propertiesMatter with the same fixed composition and properties
– Second Type of Pure SubstanceSecond Type of Pure Substance CompoundCompound
– Chemical Formula:Chemical Formula: A combination of chemical A combination of chemical symbols that show what elements make up a symbols that show what elements make up a compound and the number of atoms of each elementcompound and the number of atoms of each element Subscript:Subscript: A number written to the lower right of A number written to the lower right of
an element symbol to indicate the number of an element symbol to indicate the number of atoms of thatatoms of that
– How do you know if a substance is a compound? If it How do you know if a substance is a compound? If it is 1 thing only—and it is not on the periodic table.is 1 thing only—and it is not on the periodic table.
– Can you separate a compound? Yes—by chemically Can you separate a compound? Yes—by chemically decomposing it.decomposing it.
NaHNaH22COCO33 Mg(OH)Mg(OH)22
Decomposing a CompoundDecomposing a Compound
ElectrolysisElectrolysis– ““To tear apart with electricity”To tear apart with electricity”– The process in which electrical energy The process in which electrical energy
causes a non-spontaneous chemical causes a non-spontaneous chemical reaction to occur reaction to occur May break a compound apart into its May break a compound apart into its
elementselements Electrolysis of PbBrElectrolysis of PbBr22 & ZnCl & ZnCl22
Electrolysis of WaterElectrolysis of Water
THE GREEK PHILOSOPHERS
• 250 B.C.• Four Fundamental Elements:
Earth, Wind, Water, and Fire made up everything in the world
DEMOCRITUS
• 450 B.C.• Seashell experiment led to
development of the idea of an indivisible piece of matter called “atomos”•Atom: The building
block of matter
•Problem: No experimental data to back his concept
•Aristotle: Discredited Democritus
DEMOCRITUS’ ATOM
Law of Conservation of Mass•Antoine Lavoisier--1782 (Mercury & Oxygen Experiment)
•Mass cannot be created nor destroyed in a chemical reaction
•The mass of the reactants must equal the mass of the products in a chemical reaction
Law of Definite Proportions
• Joseph Louis Proust-1799
• In a pure compound, the elements combine in definite proportions to one another according to mass– Water is always 2 Hydrogen : 1 Oxygen
Law of Definite Proportions
Malachite
John Dalton-1803
·Elements are made of tiny particles called atoms
·All atoms of a given element are identical
·Atoms of a given element are different then every other element
·Atoms of one element can combine with atoms of another element to form compounds
·Atoms are indivisible and indestructible. Atoms can only be rearranged in chemical reactions--not created, divided, nor destroyed.
DALTON’S ATOM
Benjamin Franklin-1700’s
• Kite experiment:– Objects have 1 of
2 electric charges• Called them + &
-
• Like charges repel
• Opposite charges attract
Michael Faraday--1839
• Suggested that atoms contain particles that have electrical charge– Electricity (elektron, Greek word for amber)
• The flow of electrons in a substance– Static: Stationary
– Static Electricity: Electrical charges not in motion (socks out of a dryer)
J.J. THOMSON--1897
CATHODE RAY TUBE: Evacuated glass tube in which a stream of electrons emitted by a cathode strikes a fluorescent material, causing it to glow
CATHODE: The electrode that brings electrons to the ions or atoms in a solution.
TELEVISIONS ARE CATHODE RAY TUBES
THOMSON’S PLUM-PUDDING MODEL OF THE ATOM
Electron’s (negatively
charged particles) are
embedded in a ball of positive
charge.
Thomson measured the degree to which a magnetic field and an electric field deflected the cathode ray. Since the field was
attracted to the positive charge, he knew it must contain a negative charge. By doing this he discovered the electron.
Henri Becquerel--1896
• Accidentally placed uranium on unexposed photographic film– Found an image had been produced on the film– Discovered that uranium exhibits radioactivity
• Radioactivity is the spontaneous emission of radiation from an element
• Marie & Pierre Curie were awarded the Noble Peace Prize, along with Becquerel, for the discovery of radioactivity
• The Curies isolated two other radioactive elements—radium and polonium
• Elements with atomic numbers greater than 83 are radioactive
Radioactivity
Robert Millikan—1909Oil Drop Experiment
Using this experiment, Millikan determined the charge of the electron
Ernest Rutherford
Alpha particle (α)—a particle with a +2 charge
Beta particles ()—high-speed electrons
Gamma radiation ()—not composed of particles
RUTHERFORD’S GOLD FOIL EXPERIMENT--1911
If Thomson’s model was correct, positive α particles would all go straight through the atom. However, Rutherford’s Gold Foil Experiment proved this to be untrue. Instead, every once in a while the α particle was repelled. Since α particles are positive, that meant there was a small, positive part of the atom.
RUTHERFORD’S NUCLEAR MODEL OF THE ATOM
Concept: The atom is made of mostly empty space, containing electrons, surrounding a small, dense,
positively charged nucleus.
-- Center of the atom -- subatomic
particle with no charge located in the nucleus
-- subatomic particle with a positive charge located in the nucleus
James Chadwick—1930’s
Scanning Tunneling Microscope (STM)
STM IMAGES
Nickel Platinum
Iron on Copper
WHO RECEIVED THE NOBEL PRIZE FOR STM IN 1986?
• Gerd Binnig and Heinrich Rohrer of the IBM Research Laboratory– 1981-Invented the STM which formed images
of individual atoms
ATOM MANIPULATION
Iron on Copper
Carbon Monoxide Man (on
Platinum)
Xenon on Nickel
Particle Accelerator--FermiLab
What’s smaller than a proton?
Other particles: quarks, gluons, mesons, muons & other exotic particles—no immediate chemical
impact
Atoms are
composed of
protons, electrons &
neutrons which
explain the behavior
of matter.
ATOMIC SIZE
A typical atom is 0.000000001 meter across or 1 billionth of a meter
A quark is 0.000000000000000001 meter
ATOMIC SIZE
If the atom was the same size as the distance between the Earth and the Moon then:
-the nucleus would be the length of a golf course
-a proton would be about the size of a football field
-a quark would be about the size of a golf ball
SUBATOMIC PARTICLES
Symbol Charge (relative)
Location
Mass (relative)
Electron
e- -1 Outside nucleus
0 amu
Proton p+ +1 Inside nucleus
1 amu
Neutron
n0 0 Inside nucleus
1 amu
Amu = atomic mass units= 1/12 the mass of a carbon-12 atom
Atomic Number
= # of protons
In an ATOM also= # of _________________
because: an ATOM is electrically neutralso: the positive = the negative
protons electrons
A lithium atom with 3 protons & 3 electrons has no overall charge.
3 protons + 3 electrons =
(+3) + (-3) = 0
A boron atom with 5 protons & 5 electrons has no overall charge.
5 protons + 5 electrons =
(+5) + (-5) = 0
• The atomic number is the number that is always used to identify an element– Each element has a unique # of
protons and the number of protons of a particular element can never change
• The elements are arranged by atomic number on the periodic table
Atomic Number
Example
Element
Name
Element
Symbol
Atomic Numbe
r
# of proton
s
# of electro
ns
10
Ag
62
ISOTOPESIsotopes: Different atoms of the same element with
the same number of protons but a different number of neutrons
• What’s this mean? There are different types of the same element
• Isotopes of the same element are: chemically alike, because they have the same number of protons & electrons
90% of the universe, H2O
D2O (moderator in nuclear reactors to slow down neutrons)
Radioactive, produced in nuclear reactors, fission bombs
Carbon Isotopes
MASS NUMBER
Mass Number: The sum of the isotope’s number of protons and neutrons-The mass number is the mass of just 1 of the element’s isotopes-The mass number is always a whole number
Mass Number = (# of p+) + (# of no)Neutrons =
Mass # must be calculated, it cannot be found on the periodic table!
A P E M A NTOMIC
NUMBER
=
ROTONS
LECTRONS
&
ASS
NUMBER
TOMIC
NUMBER
EUTRONS
= +
Examples
What is the mass number of an atom with 17
protons and 20 neutrons?
How many neutrons does a carbon atom with
a mass number of 14 have?
Isotopic Symbol:Mass #
Atomic #
Naming an Isotope:Element Name-Mass #
ISOTOPES
Symbol
EXAMPLESWrite the isotopic symbols for the element with:21 protons, 24 neutrons
53 protons, 74 neutrons
How many protons, electrons and neutrons are in an atom of 32
15P?
EXAMPLE OF AN ISOTOPE
Isotope Isotopic Symbol
Mass # Atomic # # of Protons
# of Neutrons
Carbon-12
Carbon-13
Atomic Mass Unit: Unit for atomic mass• 1 amu = 1/12 (mass of carbon-12 atom)
= 1.66 x 10-24 g
Atomic Mass: a weighted average of all of the isotopes of an element
• Different from mass number• Is found on the periodic table• the atomic mass value will be closest to the mass
of the isotope that is most abundant
ISOTOPES
To calculate atomic mass:
Atomic Mass = [(% abundance isotope 1) x (mass of isotope 1)] + [(% abundance isotope 2) x (mass of isotope 2) ] + …
Example: Calculate the atomic mass of carbon if carbon-12 has a percent
abundance of 98.89% and carbon-13 has a percent abundance of 1.11%.
ATOMIC MASS