Quantum Number Keep in mind are probabilities of finding electrons in certain places doing certain things(spin). n = what energy level (1, 2, 3, 4...) l = what sub-level (s, p, d, or f) m = which orbital (s=1; p=3; d=5; f=?) s = which spin (only two possibilities up or down)

Pauli Exclusion Principle No two electrons ever have the same four quantum numbers in the same atom. Just as no two houses have the same address.

How are these organized? n = 1 n= 2 n = 3 n = 4 Level 1 sublevels Level 2 sublevels Level 4 sublevels Level 3 sublevels s s s s p p p d d f

Remember: 1s is smaller than 2s, 2s is smaller than 3s, etc. How about energy? Which has the most?

How do atoms put their electrons in these sublevels? Lowest energy levels are filled first. Sublevels are filled “s”, then “p”, then “d”, then “f”. Well, sort of...

Orbitals Principal quantum number 3s 3p 3d 4s 4p 4d 4f 1s 2s 2p 5s 5p 5d 5f 6s 6p 6d 6f 7s 7p 7d 7f s p d f

1s orbital holds two electrons e-

Then consider the next orbital: 2s (which also holds only two e-.) e-

Then consider the next orbital: 2p there are three of them (which also hold two e- each) e- This is one of three.

Electron configuration for … Scandium Look up the number of electrons (same as the number of protons). Use the diagonal rule. Scandium is #21. That means Sc has _____ electrons

Electron configuration for … Scandium

Energy level (Principle Quantum #) # of electrons (add these) Sublevel

Electron configuration for … Scandium Add These

Practice Electron configurations for: Neon Aluminum Vanadium 1s 2 2s 2 2p 6 1s 2 2s 2 2p 6 3s 2 3p 1 1s 2 2s 2 2p 6 3s 2 3p 6 4s 2 3d 3