1. Anything in black letters = write it in your notes (‘knowts’)
Chapter 5
Electrons in Atoms
Anything in black letters = write it in your notes (‘knowts’)

2. Rutherford’s Planetary Model of the Atom
5.1 – Revising the Atomic Model
Rutherford’s Planetary Model of the Atom
Electrons moving around a tiny nucleus

3. Problems with Rutherford’s Model
Did not explain the chemical properties of the elements.
Did not explain atomic spectra (…later…)
e- would spiral into the nucleus, but they don’t

4. Niels Bohr The Bohr Model ~1913
Electrons are found only in specific locations (or orbits) around the nucleus.
These orbits are called energy levels.
To move from one energy level to another, an e- must gain or lose a quantum of energy.
Niels Bohr

5. The energy levels in atoms are unequally spaced, like the rungs in this unusual ladder. The higher energy levels are closer together.

6. The Quantum Mechanical Model The modern description of e- in atoms.
Similar to Bohr Model except the exact location of an electron is impossible
Electron cloud
Electrons are likely to be found in electron ‘clouds’ around the nucleus

7. Atomic orbital –
Most probable place for e- to be.
Each orbital can hold 2 e- maximum.
The orbitals are named s, p, d & f

8. S (1 type) p (3 types) d (5 types) There are 7 types of f orbitals
Don’t worry about these shapes…

9. Maximum Electron Capacity
Orbital Name
Types of Orbital
Maximum Electron Capacity s 1 p 3 d 5 f 7
x 2 2
x 2 6
x 2 10
x 2 14
Each orbital can hold 2 e- maximum

10. Maximum Number of Electrons in Energy Level
This chart is on page 132
Summary of Principal Energy Levels and Sublevels
Energy Level
Number of Sublevels
Type of Sublevel
Maximum Number of Electrons in Energy Level
n = 1 1
n = 2 2
n = 3 3
n = 4 4
1s (1 orbital) 2 8
2s (1 orbital), 2p (3 orbitals)
3s (1 orbital), 3p (3 orbitals),
3d (5 orbitals) 18
4s (1 orbital), 4p (3 orbitals),
4d (5 orbitals), 4f (7 orbitals) 32

11. 5.2 – Electron Arrangement in Atoms
Aufbau Principle –
e- occupy the orbitals of lowest energy first.
Pauli Exclusion Principle –
Hund’s Rule –
we will not cover

12. Aufbau Diagram (p. 135) E- fill the lowest energy orbitals first
Increasing energy 6s 5s 4s 3s 2s 1s 6p 5p 5d 4p 4d 4f 3p 3d 2p
E- fill the lowest energy orbitals first
Notice the 4s fills before the 3d

13. Maximum Number of e- Due to Orbitals
Another Aufbau Diagram
(write this one down!)
Orbital
Maximum Number of e- Due to Orbitals s 2 p 6 d 10 f 14
Aufbauprinzip, (german)
"building-up principle”

14. 1s 2s 2p 2 2 3 7 Electron Configuration –
shows how e- are arranged in an atom
Example: Nitrogen
How many e-?
Which orbitals fill first and how many e- can go into each orbital?
Write the electron configuration for N 7
See aufbau diagram
# of e- in orbitals 1s 2s 2p 2 2 3

15. Your turn…
Write the electron configuration for
a) boron
b) silicon
c) sulfur

16. Can you see how the periodic table can be used as an Aufbau Diagram?

17. The Electromagnetic Spectrum (p. 139)
5.3 – Atomic Emission Spectra and the Quantum Mechanical Model
The Electromagnetic Spectrum (p. 139)
Low energy
( = 700 nm)
High energy
( = 380 nm)
Frequency  (s-1)
3 x 106
3 x 1012
3 x 1022
102
10-8
10-14

18. A prism separates light into the colors it contains
A prism separates light into the colors it contains. White light produces a rainbow of colors.
Screen
Prism
Slit
Light
bulb

19. Light from a helium lamp produces discrete lines.
Screen
Slit
Prism
Helium
lamp

20. The lines that result are unique for each element and are called its atomic emission spectrum.

21. Bohr’s Model explained the emission spectra
When an atom absorbs energy an electron jumps to a higher energy level (excited state).
The electron returns to the lower energy level, emitting a photon with a definite energy.
The photon’s energy shows up as a line in the emission spectrum.

23. Chapter 5 Quick Quiz
Explain the main difference between the Bohr Model and the Quantum Model of the atom.
How many electrons can be an atomic orbital?
How many types of s, p, d, and f orbitals are there?
s = ______, p = _______, d = ______, f = ______
What is the maximum e- capacity of the
s orbitals ____, p orbitals ____, d orbitals ____, f orbitals ____

24. Write the electron configuration for the following elements.
Helium
Strontium
Aluminum
Chlorine
Silver
Arsenic

25. Chapter 5 Things to Know…
Rutherford  Bohr  Quantum Mechanical Models,
Energy Levels, Atomic Orbitals (s, p, d, f) ,
Aufbau Principle & Diagram,
Electron Configurations,
Explanation of Atomic Emission Spectra