1. Electron Energy Levels
Electrons have different energy levels
The farther the electron is from the nucleus, the more energy the electron has
Electrons “fill” the energy levels from just outside the nucleus, outward
Each of the seven energy levels have a maximum number of electrons they can hold
Energy level 1 = up to 2 electrons
Energy level 2 = up to 8 electrons
Energy level 3 = up to 18 electrons
Energy level 4 = up to 32 electrons
Etc.

2. Electron Configuration

3. Electron Energy Levels
Scientists keep track of the electrons to help predict an element’s behavior
The electron(s) in the highest (outermost) energy level define the chemical properties of the element and participate in chemical reactions (valence electrons)
Elements in the same group (vertical columns of elements in the periodic table with similar properties) have the same number of electrons in their outer energy level

4. Electron Configuration
The electron total for each element increases by 1 left to right on the periodic table
When a period ends at the far right side, the outer energy level is filled
All energy levels have sublevels called orbitals
s orbital: holds up to 2 electrons
p orbital: holds up to 6 electrons
d orbital: holds up to 10 electrons
f orbital: holds up to 14 electrons

5. Orbital Shapes

6. Electron Configuration
Steps for determining the electron configuration of an element:
Determine the number of electrons the element has.
Fill the lowest energy levels first and work your way up from the nucleus.
Each orbital “box” gets one up arrow and one down arrow.
Up arrows fill first, down arrows last.
Write the electron configuration.
(energy level number)(orbital) (electrons)

7. Orbital Diagram

8. Example: Fluorine Fluorine has 9 electrons.
Fill the lowest energy levels first and work your way up from the nucleus.
Each orbital “box” gets one up arrow and one down arrow.
Up arrows fill first, down arrows last.

9. Orbital Diagram for Fluorine

10. Example: Fluorine Fluorine has 9 electrons.
Fill the lowest energy levels first and work your way up from the nucleus.
Each orbital “box” gets one up arrow and one down arrow.
Up arrows fill first, down arrows last.
Write the electron configuration.

11. Orbital Diagram for Fluorine
1s22s22p5

12. Orbital Diagram

13. Notice a Pattern?