Configurations, Spin, and Ionization Energy

Filling Order of Orbitals in Multielectron Atoms 1s 2 2s 2 2p 6 3s 2 3p 6 4s 2 3d 10 4p 6 5s 2 …

Writing e- Configurations Oxygen (8 e-) Spectroscopic Notation: 1s 2 2s 2 2p 4 Orbital Box Notation: 1s 2s 2p

Isoelectronic Series Isoelectronic = same e- configuration Properties within series are affected by Z e.g., ion size decreases as Z increases Mg 2+ Na + O 2- F-F- increasing nuclear charge (Z) 10 e- in each: 1s 2 2s 2 2p 6 Z =

Ionization Energy E of e- removal from an atom or ion in the gas phase A(g) A + (g) + e- ;  E = IE 1 = 1st IE A + (g) A 2+ (g) + e- ;  E = IE 2 = 2nd IE Always positive. Why?

Trends in First IE increases decreasesdecreases

Ionization Energy Whatever increases E of e- decreases IE Down a group: larger n ˝ lower IE Across a period: increasing nuclear charge increases IE several anomalies

IE 1 Values for First 20 Elements (Problem 4)

Why is IE 1(N) > IE 1(O) ? O: 1s 2 2s 2 2p 4 N: 1s 2 2s 2 2p 3 e - - e - repulsion (spin pairing E) in the first 2p orbital makes e- a little easier to remove than unpaired e- in a N 2p orbital Is 2s 2p

High IE Values Be: 1s 2 2s 2 ; B: 1s 2 2s 2 2p 1 Elements with filled shells (noble gases) Elements with filled subshells IE Be > IE B Elements with half-filled subshells IE N > IE O