1. Electron Configuration
There are three ways to account for the electrons around atoms:
Energy Level Notation
Sublevel Notation
Orbital Diagrams

2. Energy Level Notation
Energy Level Notation – the number of electrons in a principal energy level is given, with dashes in between:
For Carbon (C)
This means two electrons in the first energy level (the maximum)
Four electrons in the second energy level
For the regents exam, this simple system is what you need to know. For this class, you will have to go a bit further.

3. Energy Level Electron Configuration
Electron configuration is located directly below the atomic number on your periodic table.

4. Energy Level Notation Questions
What is the electron configuration of Cl?
How many electrons in the highest energy level of calcium?
Atoms like to complete their “shells” of electrons. How many electrons does oxygen need to do this?
When lithium loses an electron, it now has the configuration of what noble gas?

6. Sublevel Notation
This method is more complicated, but tells you much more about the electrons around atoms, and about physical and chemical properties of atoms.
There are four types of sublevels: s, p, d, f
Energy levels are put in front of the sublevel
The number of electrons in that sublevel is a superscript
For Li: 1s22s1 (2-1 in energy level notation)
For C: 1s22s22p2 (2-4 in energy level notation)

7. What is the sequence of sublevels?
1s  2s  2p  3s  3p  4s  3d
2e e e e e e e-

8. Sublevel Notation Problems
What is the electron configuration of fluorine?
What is the electron configuration of sodium?
How many electrons in the 2p sublevel of boron?
Which element has 2 electrons in its 3p sublevel?
Which atom has to gain three electrons to attain the following noble gas configuration?
1s22s22p6

9. H □ Orbital Diagrams He □ Li □□
These are very useful, but unwieldy at times. They reveal the most information about elements physical and chemical properties.
Each orbital is represented with a box:
H □ 1s
He □ 1s
Li □□
1s s

10. Remember Rules Electrons go into lowest energy level first
In a sublevel, empty orbitals before partially filled ones
No more than 2 electrons per orbital, opposite “spins”

11. Excited States
An electron configuration can be used to designate an excited state:
Ground state for Carbon: 2-4
Possible excited state: 2-3-1
How can you distinguish ground state from excited state?
Make sure lower energy levels are full!

12. Ground State or Excited State?
1-4
2-1-2
2-8-3
Assuming that these are all neutral atoms, name the element!

13. Ground State or Excited State?
1s22p2
1s22s22p2
1s22s22p53s1
[Ne]3p1
[Ar]4s2
[Ar]4s23d104p2
Name the elements, assuming all are neutral atoms.