Atomic theoryAtomic theoryAtoms: Atoms:

The Building The Building Blocks of Matter 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

A little after that…1897

JJ Thomson Cathode Ray Tube Discovers the electron is negative

And a little after that…

Goldstein (1886) Discovers canal rays (proton)

Milliken (1909) Oil drop experiment finds the charge on an e-

Rutherford’s Gold Foil Experiment

And after all that…1911

And after all that…

Ernest Rutherford Gold Foil Experiment Discovers the Nucleus

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

Models of the atom

Bohr Electrons are

found in specific energy levels

Like planets around the sun

More on Models

Electron Cloud or Quantum Mechanical Model Electrons are in continuous motions and are shown

as a probability cloud

Needless Cartoonage

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 Electromagnetic Spectrum

Organizes light waves by energy, wavelength, and frequency

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.