Chemistry - Exam 2

Newton’s theory

tiny particles of light, a rainbow of colors combined 

Young’s theory

interference → wave behavior.

Maxwell

electromagnetic waves, predicting light behavior as waves.

Wavelength (λ)

distance between peaks (m, nm)

Frequency (ν)

cycles per second (Hz).

Amplitude

half distance between peak & trough.

Speed of light

c = 2.998 × 10^8 m/s.

Electromagnetic spectrum

visible light is a small part; color corresponds to wavelength/frequency.

Planck’s theory

Energy is quantized (like stairs, not ramps).

planck’s constant

h = 6.626 × 10^–34 J·s

Finding frequency (f) from wavelength (λ)

Use the equation f = c/λ. 

Finding wavelength (λ) from frequency (f)

Use the equation λ = c/f

Finding energy (E) from frequency (f)

Use the equation E = hf

photoelectric effect

Shows electrons absorb discrete photon energy.

bohr model

electrons orbit the nucleus in quantized energy levels, absorbing or emitting photons when moving between them.

energy quantization in bohr model

-2.178 × 10–18

Spectral lines

Bright or dark lines showing the specific wavelengths of light emitted or absorbed when electrons change energy levels.

de Broglie hypothesis:

Particles (like electrons) have wave properties.

• λ = h/(mu), where m = mass, u = velocity.

Davisson-Germer experiment

confirmed electrons behave like waves.

Principal quantum number (n)

• Energy level / shell.

• n = 1, 2, 3…

• Larger n = higher energy, farther from nucleus.

Angular momentum quantum number (ℓ)

• Defines orbital shape.

• Values: 0 to n – 1.

• ℓ = 0 → s (sphere), ℓ = 1 → p (dumbbell), ℓ = 2 → d, ℓ = 3 → f.

Magnetic quantum number (mℓ)

• Orientation of orbital.

• Values: –ℓ … 0 … +ℓ.

• Number of orbitals in subshell = 2ℓ + 1.

• Example: p (ℓ = 1) → mℓ = –1, 0, +1 → 3 orbitals.

Spin quantum number (ms)

• Electron spin = +½ or –½.

Pauli Exclusion Principle:

• No two electrons can have the same 4 quantum numbers.

• Max electrons per orbital = 2 (opposite spins).

Max electrons per subshell

• s: 2

• p: 6

• d: 10

• f: 14