Modern Atomic Theory -- AP Chem

C

speed of light; 2.998\cdot10^8 m/s

Visible Light

380 nm - 750 nm

Planck

energy cab only be absorbed or released in units of hv

h = 6.626\cdot10^{-34} J\cdot s

Einstein

Photoelectric effect: bombarding an atom with photons to knock electrons off

E = hv

Rydberg

calculate the wavelength of light when an e- makes a transition

\frac{1}{\lambda}=R\left(\frac{1}{nf^2}-\frac{1}{ni^2}\right)

R = 1.0974\cdot10^7m^{-1}

Louis de Broglie

wavelength of a particle is dependent on its mass and velocity

\lambda=\frac{h}{mv}

m = mass in kg; v = velocity in m/s

Heisenberg Uncertainty Principle

we cannot simultaneously know both the momentum and position of an electron

Schrödinger

used wave equations to determine the probability density of an electron’s location

an orbital is where an electron is 90% of the time

Pauli Exclusion Principle

no two electrons can occupy the same quantum state

if two electrons share the same orbital, they must spin in opposite directions

Aufbau Principle

electrons first fill sub-shells of the lowest available energy, then fill sub-shells of higher energy

Hund’s Rule

for any given sub-shell, electrons first fill each orbital singly with parallel spins before any orbital is doubly occupies

Ionization Trend

increases down a group and across a period

F has greatest IE

Fr has lowest IE

IE Trend EXCEPTIONS

2A→3A IE decreases: 2s electrons shield 2p electrons well but do not shield each other well

5A→6A IE decreases: paired electrons in 6A orbitals repel each other and lower IE and a half full shell in 5A is stable, less willing to lose electrons

Electron Affinity

the amount of energy released when an electron is added (anion formed)

increases (in magnitude) across a period and down a group

EA Trend Exceptions

N has a positive EA: N has a half full valence p block as a neutral atom. Adding electrons increases electron repulsion. There is no d block to move e- to.

Be & Mg have a positive EA: a full s orbital is more stable than a full s and a partially full p block

P2 is much smaller in EA magnitude than P3: P2 has extremely small p orbitals that the electron repulsions are significant enough to minimize EA

Hund’s Rule Exceptions

Group 11B Cu: [Ar] 4s2 3d9 4s1 3d10

Group 6B Cr: [Ar] 4s2 3d4 4s1 3d5