Bohr Model Of Atom

Spectrum Continuous spectrum is the

rainbow of colors containing all wavelengths

Line spectrum contains only certain colors or wavelengths

When gases are given energy, they emit line spectra which are characteristic of that gas

Continuous Spectrum

Line Spectrum of Hydrogen

Niels Bohr Said electrons occupy the atoms in

quantized energy levels Each level (orbit) is assigned an

integer (n) called the principal quantum number

As n increases, the radius of orbit is greater

Energy Energy of the electron depends on

the level it occupies

En = - RH ( 1/n2)

RH is called the Rydberg constant

RH = 2.18x10-18 J

Coulomb’s Law The energy comes from the potential

energy resulting from a separation between a positive and negative charge

Coulomb’s law describes this

q1 and q2 are the two charges

r is the distance between the charges k = 2.31 x 10-19

1 2q qE k

r

When electrons occupy the lowest possible energy level, they are in ground state

When in higher levels, they are in excited state

Hydrogen Line Spectrum H atom absorb a quantum of

energy Energized electron “jumps” to a

higher level When it falls back down, it gives off

energy as a photon of light The frequency of the light depends

on the levels it falls from and to

Equation

ΔE = Ef – Ei

hν = RH ( 1/nf2 - 1/ni

2)

frequency of light given off depends on the level transition

Example 1 Calculate the frequency and

wavelength of light given off when an electron in a H atom falls from n=4 to n=2. What color is it?

Ionization of Energy Energy that would be needed to

completely remove the electron; make it go from n = 1 to n = ∞

Example 2 Calculate the energy required to

ionize an electron from the ground state.