EM Spectrum

c = ν x λ c = 3.00 x 10 ⁸ m/sec

(speed of light)

ν = frequency

(Hz, 1/sec, sec^-1)

λ = wavelength

(meters)

Radiation travels

· in wave-like motion

· in pkts of E called photons

Quantum of E: fixed amt of E in photon

E = h ν h = 6.63 x 10 ^-34 J x sec

(Planck’s const)

Photoelectric Effect

E needed to overcome attraction of e- to nucleus in metal

Found only certain ν of light eject e- (need quantum of Energy, not more intense light)

(E = hv)

When ν ↑, e- emitted faster (↑ KE)

H atom

Continuous Spectrum: continuous (blend) light colors (ROYGBIV in prism)

Line Spectrum: radiation of only specific colors observed

Balmer: 1885 analyzed H line Spectrum

Visible radiation that was emitted followed equation:

ν = C (1 - 1 ) n = 3, 4, 5,6

(2² n²)

Other series observed:

Lyman (n_f = 1) Balmer (n_f = 2)

Paschen (n_f = 3) Brackett (n_f = 4)

Bohr (solar syst) model of atom e- only allowed in certain energy states (orbits) with certain radius

§ connected quantum idea with already observed phenomenon (H line spectrum)

§ e- can jump from one E level to another by absorbing or emitting certain amts (quanta) of E

described E of e- in equation:

En = -R_H (1 ) n = 1,2,3,4,… (princ. Q.N.)

n²

R_H = 2.18 x 10 ^-18 J (Rydberg const)

(Radius of orbit ↑ as n ↑ )

(Energy of e- ↑ (less negative) as n ↑ )

E calculated from E = hv

∆E = R_H (1 - 1 ) n_i² = init. E state of e-

n_i² n_f² n_f² = fin. E state of e-

+ ∆E = energy absorbed (e- move to higher E state)

- ∆E = energy emitted (e- moves to lower E state)

Equation ONLY DESCRIBES 1 e- atoms (H, He⁺)

Matter Waves

De Broglie: e- moving around nucleus has certain λ, so all matter can show wave-like behavior

λ = h h = 6.63 x 10 ^-34 J x sec

m x v p = momentum, m x v

m = mass (kg)

v = velocity m/sec

(See AP Test equation sheet!)