Electron Configuration  Shorthand way of writing electron configuration of atoms 10 Ne: 1s 2 2s 2 2p 6 Elemental Symbol and atomic number Principal energy level Energy sublevel Number of electrons

zShorthand Configuration S 16e - Valence Electrons Core Electrons S16e - [Ne] 3s 2 3p 4 1s 2 2s 2 2p 6 3s 2 3p 4 Valence Electrons  Longhand Configuration

Valence Electrons  Valence Electrons  As (atomic number 33)  1s 2 2s 2 2p 6 3s 2 3p 6 4s 2 3d 10 4p 3  The electrons in the outermost energy level.  s and p electrons in last shell  5 valence electrons

[Ar] 4s 2 3d 10 4p 2 Noble Gas Configuration  Example - Germanium X X X X X X X X X X X X X

Electron Configuration Let’s Practice  P (atomic number 15)  1s 2 2s 2 2p 6 3s 2 3p 3  Ca (atomic number 20)  1s 2 2s 2 2p 6 3s 2 3p 6 4s 2  As (atomic number 33)  1s 2 2s 2 2p 6 3s 2 3p 6 4s 2 3d 10 4p 3  W (atomic number 74)  1s 2 2s 2 2p 6 3s 2 3p 6 4s 2 3d 10 4p 6 5s 2 4d 10 5p 6 6s 2 4f 14 5d 4 Noble Gas Configuration [Ne] 3s 2 3p 3 [Ar] 4s 2 [Ar] 4s 2 3d 10 4p 3 [Xe] 6s 2 4f 14 5d 4

Energy Sublevels Labeled s, p, d, or f –Based on shape of the atom’s orbitals

Electron Configuration Your Turn  N (atomic number 7)  1s 2 2s 2 2p 3  Na (atomic number 11)  1s 2 2s 2 2p 6 3s 1  Sb (atomic number 51)  1s 2 2s 2 2p 6 3s 2 3p 6 4s 2 3d 10 4p 6 5s 2 4d 10 5p 3  Cr (atomic number 24)  1s 2 2s 2 2p 6 3s 2 3p 6 4s 2 3d 4 Noble Gas Configuration [He] 2s 2 2p 3 [Ne] 3s 1 [Kr]5s 2 4d 10 5p 3 [Ar] 4s 2 3d 4

Why are d and f orbitals always in lower energy levels? d and f orbitals require amounts of energy It’s better (lower in energy) to that requires a large amount of energy (d and f orbtials) for one in a higher level but lower energy This is the reason for the diagonal rule! LARGE skip a sublevel BE SURE TO FOLLOW THE ARROWS IN ORDER!

 Full energy level  Full sublevel  Half full sublevel Stability

Exceptions  Copper  Expect: [Ar] 4s 2 3d 9  Actual: [Ar] 4s 1 3d 10  Silver  Expect: [Kr] 5s 2 4d 9  Actual: [Kr] 5s 1 4d 10  Chromium  Expect: [Ar] 4s 2 3d 4  Actual: [Ar] 4s 1 3d 5  Molybdenum  Expect: [Kr] 5s 2 4d 4  Actual: [Kr] 5s 1 4d 5 Exceptions are explained, but not predicted! Atoms are more stable with half full sublevel

Stability  Atoms create stability by losing, gaining or sharing electrons to obtain a full octet  Isoelectronic with noble gases Atoms take electron configuration of the closest noble gas

Stability  Na (atomic number 11)  1s 2 2s 2 2p 6 3s 1  1s 2 2s 2 2p 6 = [Ne] Na 1 Valence electron Metal = Loses Ne

Try Some  P -3 (atomic number 15)  1s 2 2s 2 2p 6 3s 2 3p 6  Ca +2 (atomic number 20)  1s 2 2s 2 2p 6 3s 2 3p 6  Zn +2 (atomic number 30)  1s 2 2s 2 2p 6 3s 2 3p 6 3d 10  Last valence electrons (s and p) Full Octet