1. Electron Configuration
Electrons in Atoms
Electron Configuration

2. Energy levels, sublevels and orbitals
(cloud or shell)
Sublevels
Orbitals
Number of electrons 1 s
1 s orbital 2
s, p
3 p orbitals 8 3
s, p, d
5 d orbitals 18
4, 5, 6, 7
s, p, d, f
7 f orbitals 32

3. s orbitals 3s 2s 1s

4. Three p Orbitals px pz py

5. A. General Rules Pauli Exclusion Principle
Each orbital can hold TWO electrons with opposite spins.

6. A. General Rules Aufbau Principle
Electrons fill the lowest energy orbitals first.

7. A. General Rules WRONG RIGHT Hund’s Rule
Within a sublevel, place one e- per orbital before pairing them.
“Empty Bus Seat Rule”
WRONG
RIGHT

8. 1s2 2s2 2p4 O B. Notation 1s 2s 2p 8e- Orbital Diagram
Electron Configuration
1s2 2s2 2p4

9. S 16e- 1s2 2s2 2p6 3s2 3p4 S 16e- [Ne] 3s2 3p4 B. Notation
Longhand Configuration
S 16e-
1s2
2s2
2p6
3s2
3p4
Core Electrons
Valence Electrons
Shorthand Configuration
S 16e- [Ne] 3s2 3p4

10. C. Periodic Patterns s p d (n-1) f (n-2) 1 2 3 4 5 6 7 6 7
© 1998 by Harcourt Brace & Company

11. C. Periodic Patterns Period # (Row)
indicates the highest energy level (subtract for d & f)
Group # (column)
Indicates the total # of valence e-
Column within sublevel block
# of e- in sublevel

12. 1s1 C. Periodic Patterns 1st column of s-block 1st Period s-block
Example - Hydrogen
1s1
1st column of s-block
1st Period
s-block

13. C. Periodic Patterns p s d (n-1) f (n-2) Shorthand Configuration
Core e-: Go up one row and over to the Noble Gas.
Valence e-: On the next row, fill in the # of e- in each sublevel. s
d (n-1)
f (n-2) p

14. C. Periodic Patterns
Example - Germanium
[Ar]
4s2
3d10
4p2

15. D. Stability Full energy level Full sublevel (s, p, d, f)
Half-full sublevel

16. D. Stability Electron Configuration Exceptions Copper
EXPECT: [Ar] 4s2 3d9
ACTUALLY: [Ar] 4s1 3d10
Copper gains stability with a full d-sublevel.

17. D. Stability Electron Configuration Exceptions Chromium
EXPECT: [Ar] 4s2 3d4
ACTUALLY: [Ar] 4s1 3d5
Chromium gains stability with a half-full d-sublevel.

18. D. Stability 1+ 2+ 3+ NA 3- 2- 1- Ion Formation
Atoms gain or lose electrons to become more stable.
Isoelectronic with Noble Gases. 1+ 2+ 3+ NA 3- 2- 1-

19. D. Stability Ion Electron Configuration
Find the Noble Gas with the same number of electrons and write its symbol in brackets
EX: Oxygen ion  O2- = 10 electrons
= [ Ne ]
Ex: Potassium ion  K+ = 18 electrons
= [Ar]

20. Line Emission Spectrum
The lowest energy state of an atom is called the ground state
A state in which an atom has a higher potential energy than the ground state is called an excited state
When an excited atom returns to the ground state, it gives off energy, usually in the form of light

21. Line Emission Spectrum
When this light is shined through a prism, it is separated into a series of specific frequencies of light
The bands of light are known as the line emission spectrum for the element
Line emission spectrum for hydrogen

22. Photoelectric Effect
The emission of electrons from a metal when light shines on the metal
only occurs if the photons in the light have a certain minimum frequency (energy)
Different metals require different minimum frequencies