Comprehensive Light Properties, Electron Configurations, and Ion Formation for Chemistry Students

Wavelength (λ)

distance between crests (m).

Frequency (ν)

cycles per second (Hz, s⁻¹).

Speed (c)

3.00 × 10⁸ m/s.

c = λν

Formula relating speed, wavelength, and frequency.

E = hν

Energy formula where h = 6.626 × 10⁻³⁴ J·s.

E = hc / λ

Another formula for energy in terms of wavelength.

Emission Spectra

Atoms emit unique spectral lines when excited electrons fall back down → acts as a fingerprint for each element.

Green aurora light

Example with λ = 558 nm → E ≈ 3.56 × 10⁻¹⁹ J.

Energy levels (n)

correspond to periods on periodic table.

Sublevels

s, p, d, f.

Orbitals

s = 1, p = 3, d = 5, f = 7.

Filling Rules

Aufbau principle - fill lowest energy first.

Pauli exclusion

2 e⁻ per orbital, opposite spins.

Hund's rule

fill orbitals singly before pairing.

Max Electrons

s = 2, p = 6, d = 10, f = 14.

Oxygen (Z=8)

Example: 1s² 2s² 2p⁴.

Noble Gas Shorthand

Use the nearest noble gas in brackets.

Stability

Full sublevel (s², p⁶, d¹⁰) = most stable.

Half-full

s¹, p³, d⁵ = also stable.

Exceptions

Chromium: [Ar] 4s¹ 3d⁵ (half-filled d).

Copper

[Ar] 4s¹ 3d¹⁰ (full d).

Excited Electrons

Electrons absorb energy and jump to higher orbitals.

Valence Electrons

Outermost electrons = determine reactivity.

Octet rule

stable with 8 e⁻ (He stable with 2).

Lewis Dot Structures

Show only valence e⁻ as dots.

Ions

Cations (metals): lose e⁻, positive; Anions (nonmetals): gain e⁻, negative.

Isoelectronic

ions with the same electron configuration.

Naming Cations

element + "ion" (Ca²⁺ = calcium ion).

Naming Anions

element root + "-ide" (Cl⁻ = chloride).

Multivalent Metals

Some metals (esp. transition) form multiple charges.

Roman Numerals in Compounds

Indicated with Roman numerals.