2. Electrons Core electrons Valence electrons Energy Levels
Electrons found in the inner shells
Valence electrons
Found in the outermost shell of an atom
Energy Levels
Each layer or shell is considered one energy level.

4. An element’s period number indicates the energy level of the element’s valence electrons.

5. Qwizdom Questions
Which of the following elements have valence electrons in Energy Level 1? He B Si
Which of the following elements have valence electrons in Energy Level 3?

6. Electron Configuration
An electron’s “address” has four parts
Energy level (1-7)
Describes how far the electron is from the nucleus
Energy sublevel (1s, 2s, 2p, 3s, 3p, 4s, 3d…)
Describes what type of orbital an electron is in
Contains one or more orbitals

8. Orbital (s,p,d,f)
Describes the shape of space an electron occupies
Can hold up to two electrons
Superscript (1s1, 2p4, 4d8…)
Indicates how many electrons are in each sublevel

10. # of Orbitals 1 3 5 7

11. Filling in Orbital Diagrams
Find number of electrons
Start adding electrons starting with first sublevel (1s)
When a sublevel is completely filled, move on to next sublevel following the correct order
Always add up arrow first.
Once all orbitals in a sublevel have an up arrow, then you can add 2nd electron (down arrow)

19. Energy Level 1 H 1s1 He 1s2
Energy Level 2 Li 1s2 2s1 Be 1s2 2s2
B 1s2 2s2 2p1 C 1s2 2s2 2p2 N 1s2 2s2 2p3