Chemistry- Unit 5: Atomic Theory

Democritus

Democritus

Matter is made up of indestructable, indivisible, solid particles

John Dalton

1) Matter is composed of atoms: indivisible, indestructable, solid spheres
2) Atoms of same element: identical properties
Atoms of different element: different properties
3) Atoms can't be created, destroyed, or changed
4) Chemical rxn is rearrangement of atoms

Law of Multiple Proportions

2 elements form 1+ compound, ratio of masses will be small whole numbers

Tomson and Crookes

Discovered the electron
- Crooke's Tube
- Plum Pudding Model: atom is fully positive with negative embedded in it

Rutherford

Most particles went through gold foil BUT SOME BOUNCED BACK - when (+) alpha particles collided with + nucleas

# of electrons (in a neutral atom) =

# of protons

# of electrons (in a positve ion)

# of protons - charge #

# of electrons (in a negative ion)

# of protons + charge #

# of protons =

atomic #

# of neutrons =

mass # - atomic #

atomic mass =

(isotope mass x %) + (isotope mass x %) ...

to find frequency or wavelength

C= λv

to find energy or frequency (plancks hypothesis)

E = hv

Bohr atomic model

• Electrons orbit only at certain allowed orbits or specific energy level

How is bright-light spectrum formed?

1) ground state: lowest possible energy level
2) atom absorbs NRG (light, electricity, heat, collisions..)
3) excied state: electron moves to higher energy state
4) electron falls back to ground state and releases NRG as photons of light

photon/nucleon

a particle of light