17 The Atomic Nature of Matter Atoms are the building blocks of most matter.
Atomic theory Atoms: The Building Blocks of Matter.
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Transcript of Atomic theory Atoms: The Building Blocks of Matter.
First, there was Democritus
Democritus is not a foot fungus, he was a Greek philosopher
“atomos” He came up with the idea
of the atom around 400BCE He had no evidence, he
just thought that that wasjust the way the world should work
This guy thought he was nuts
His name is Aristotle He is the most famous and
most influential of the Greek philosophers
Too bad for Democritus And atomic theory
A brief history of the atom…
Democritus: “atomos” No experiments…not believed
Aristotle: 4 elements make up everything
Earth Air Fire Water
4th century BCE
Ancient Greece
Gold Go ld
The word “atom” comes from a Greek word
that means “unable to be cut”
Imagine you had a piece of gold that you then cut in half…
…and then you cut one of these smaller pieces in half…
… and you kept on cutting the leftover piece in half…
The word “atom” comes from a Greek word
that means “unable to be cut”
…and kept going… …and kept
going…
…and kept going…
Eventually you would have 1 piece of gold left. If you cut it in half, you wouldn’t
have gold any more – you’d have something
else. This tiny, tiny single piece of gold is called an atom of gold. An atom is the smallest particle of an element that acts like the
element.
An atom of gold
Hundreds of years later… Law of Conservation of MassLaw of Conservation of Mass
(1789)(1789)
Total mass of reactants =
Total mass of products
Antoine Lavoisier
Mass is neither created nor destroyed during chemical or physical reactions.
Soon after that… John Dalton
Atomic Theory1. All matter is made up of tiny, indivisible particles
called atoms.2. Atoms of the same element are identical – same
physical and chemical properties3. Atoms of different elements are different –
different physical and chemical properties4. Atoms can chemically combine in whole number
ratios to form compounds and physically mix to form mixtures.
5. An atom cannot be changed into an atom of a different element by a chemical change – they may be combined, separated, or rearranged, but never created, destroyed, or changed.
Early 1800’s
England
And a little after that…
Goldstein (1886) Discovers canal rays (proton)
Milliken (1909) Oil drop experiment finds the charge on an e-
Models of the Atom
Dalton Model Solid Sphere
Thomson Model Blueberry Muffin
blueberries = electrons cake/muffin = positive matter
e-
Positive material
Models of the atom
Rutherford Model Dense, positive nucleus
Electrons revolving around nucleus in circular or elliptical orbits Mostly empty space
More on Models
Electron Cloud or Quantum Mechanical Model Electrons are in continuous motions and are shown
as a probability cloud
Orbitals
Orbital- the area around the nucleus in which it is most likely to find an electron.
The come in a variety of shapes and sizes!!!
S P D F
Sphere peanut daisy/donutfunkadelic
Orbital Shapes
Check out this site for cool pics of orbitals!!!!!!!!!!
1 type 5 types3 types 7 types
Starting Electron Configurations
You have an address, so does an electron.
Most general = energy level (1, 2, 3, etc)
sub- level (s, p, d, or f)
degenerate orbital
Most specific = spin
Electron Configuration Rules
The Rules Aufbau Principle- electrons fill lowest energy
orbitals first. Pauli Exclusion Principle- electrons will
spread out into degenerate orbitals before pairing.
Hund’s Rule- electrons in the same orbital will have opposite spins (one up and one down)
The Diagonal Rule Tells the order of the energy of the orbitals
7s 7p 7d 7f6s 6p 6d 6f5s 5p 5d 5f4s 4p 4d 4f3s 3p 3d2s 2p1s
Configuration Diagrams
Place all up arrows in first
Try to create someDiagrams at this
Websitehttp://www.wellesley.edu/Chemistry/chem120/elecconfigdrag.html
Only two arrowsper box
An electron is represented by
an arrow
Electron Configurations
These are the same as the boxes, only they take up less space
Large # = energy level Letter = orbital shape superscript = how many electrons
Element # 19, Potassium:1s22s22p63s23p64s1
Noble Gas Notation
Look for the noble gas that comes before the element you are trying to describe.
Write the noble gas symbol in brackets [ ] Follow the symbol with the remaining
orbitals that are necessary to account for all the electrons in the desired element.
The photoelectric effect Photon
a particle of light that contains a specific amount of energy (quantized)
The photoelectric effect a photon of light hits and energizes
an electron in an atom. This causes the electron to jump to a higher energy level. The electron inevitably falls back down to the lower energy level, and releases light.