Chapter 30

The Nature of

the Atom

30.1 Rutherford Scattering and the Nuclear Atom

In its natural state, an atom is electrically neutral.

30.1 Rutherford Scattering and the Nuclear Atom

A Rutherford scattering experiment.

30.2 Line Spectra

The individual wavelengths emitted by two gases and thecontinuous spectrum of the sun.

30.2 Line Spectra

The Line Spectrum of Hydrogen

Lyman series

Balmer series

Paschen series

,4,3,2 1

1

1122

n

nR

,5,4,3 1

2

1122

n

nR

,6,5,4 1

3

1122

n

nR

30.3 The Bohr Model of the Hydrogen Atom

In the Bohr model, a photon is emitted when the electron dropsfrom a larger, higher-energy orbit to a smaller, lower energyorbit.

hfEE fi

30.3 The Bohr Model of the Hydrogen Atom

THE ENERGIES AND RADII OF THE BOHR ORBITS

r

kZe

r

kZemv

E

2

EPEKE

2

22

21

30.3 The Bohr Model of the Hydrogen Atom

,3,2,1 2

nh

nrmvL nnn

,3,2,1 4

2

22

2

n

Z

n

mke

hrn

,3,2,1 m1029.52

11 nZ

nrn

Radii for Bohr orbits

Angular momentum is quantized.

30.3 The Bohr Model of the Hydrogen Atom

,3,2,1 2

2

2

2

422

n

n

Z

h

emkEn

,3,2,1 J1018.22

218 n

n

ZEn

,3,2,1 eV 6.132

2

nn

ZEn

Bohr energy levels

30.3 The Bohr Model of the Hydrogen Atom

ENERGY LEVEL DIAGRAMS

30.3 The Bohr Model of the Hydrogen Atom

Example 3 The Ionization Energy of Li2+

Li2+ is a lithium atom (Z=3) with only one electron. Obtain the ionizationenergy of Li2+.

eV 1221

3eV 6.13eV 6.13

2

2

2

2

n

ZEn

eV 122energy Ionization

30.3 The Bohr Model of the Hydrogen Atom

THE LINE SPECTRA OF THE HYDROGEN ATOM

fifi

if

nnnn

nnch

emk

,3,2,1,

11

Z 21

222

3

422

30.4 De Broglie’s Explanation of Bohr’s Assumption About Angular Momentum

De Broglie suggested standing particle waves as an explanationfor Bohr’s angular momentum assumption.

,3,2,1 2 nnr