Chem Unit 2 Review

Chemistry Unit 2

Aristotle

Believed all matter was made of 4 elements, proven wrong.

Democritus

Proposed that matter was made of invisible particles (atoms)

Dalton

Proposed the first modern atomic theory although corrected and modified over time.

Thomson

Discovered the electron; created the “plum pudding” model where electrons are inside a positive sphere.

Rutherford

Discovered the nucleus; an atom is mostly empty space (father of nuclear physics)

Bohr

Proposed the solar system model, electrons orbitted the nucleus in fixed paths. (Proven false and model only for hydrogen)

Quantum mechanical model (wave model)

Describes electrons as waves occupying regions of space (orbitals) or electron clouds.

Aufbau principle

Fill lowest energy levels first.

Hund’s rule

Spread out electrons in orbitals before pairing up. (1/orbital)

Pauli exclusion principle

Two electrons in the same orbital must have opposite spins (In orbital notation: ↑↓)

Isotope

Elements with same protons but different neutrons.

n=3

Infrared

n=2

Visible

n=1

Ultraviolet

h

Plank’s constant: 6.626x10^-34

c

Speed of light constant: 3.00×10^8

Chadwick

Founded the neutron

Energy equation

E=hv

Frequency equation

v=\frac{c}{\lambda}

Speed of light

c=\lambda v

Absorption

Electron absorbs energy and moves to higher energy (n=1>n=3, UV light absorbed)

Emission

Electrons release energy and moves to lower energy (n=3>n=2, visible light is emitted)

Energy in ROYGBIV

Increases R>V

Decreases V>R

Wavelength and frequency

Inversely related

Energy and wavelength

Inversely related

Energy and frequency

Directly related

Exceptions to electron distribution

Copper (Cu) and Chromium (Cr)