CHAPTER 6

ELECTRONIC STRUCTURE OF ATOMS

Almost everything we now know about electrons came

from the study of light.

Light is a type of electromagnetic radiation.

Types of Electromagnetic Radiation

Three complete cycles of wavelength

The product of the frequency and its

wavelength equals the speed of light (c).

c =

C =

Since the speed of light is 3 x 108 m/s, there must be an inverse relationship between wavelength and frequency

The yellow light given off by a sodium vapor lamp

used for public lighting has a wavelength of 589 nm. What is the frequency of

this radiation?

The yellow light given off by a sodium vapor lamp

used for public lighting has a wavelength of 589 nm. What is the frequency of

this radiation? c = = 5.09 x 1014 s-1

Max Planck assumed that small quantities of energy (quantum) can be emitted or absorbed as

electromagnetic radiation.

E = hv Planck’s constant (h) = 6.63 x 10-34 joule-seconds (J-s)

Since yellow light has a wavelength of 589 nm, what is the smallest quantum of

energy that can be absorbed from yellow light?

Since yellow light has a wavelength of 589 nm, what is the smallest quantum of

energy that can be absorbed from yellow light?

E=hv E=(6.63 x 10-34)(5.09 x 1014)

E = 3.37 x 10-19 J

Johann Balmer observed the 4 lines of the hydrogen

spectrum to come up with a formula:

v=C(1/22-1/n2) n= 3,4,5,6

Niels Bohr assumed that electrons orbit in circular paths around the nucleus.

He also said that orbits of certain radii correspond to

certain energies.

En=(-RH)(1/n2)

n= 1, 2, 3, 4, …

n= the principal quantum number

RH = 2.18 x 10-18 J

Bohr assumed that electrons could “jump” from one

energy state to another by absorbing or emitting energy

of certain frequencies.

E= Ef - Ei = hv

By combining some equations:

v= E/h = (RH/h)(1/ni2-1/nf

2)Calculate the wavelength of light that

corresponds to the transition of the electron from the n=4 to n=2 state of the

H atom.

Heisenberg’s Uncertainty Principle:

It is impossible for us to know the exact velocity or

exact location of an electron

This is a probability

density of the location of the electron in a H atom.

This represents the shape of the s orbital.

The p Orbitals

The d Orbitals