Configurations, Spin, and Ionization Energy

Filling Order of Orbitals in Multielectron Atoms

1s22s22p63s23p64s23d104p65s2…

Writing e- Configurations

Oxygen (8 e-)

Spectroscopic Notation: 1s22s22p4

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

Mg2+ Na+ O 2-F-

increasing nuclear charge (Z)

10 e- in each: 1s22s22p6

Z = +12 +11 +9 +8

Ionization Energy

E of e- removal from an atom or ion in the gas phase

A(g) A+(g) + e- ; E = IE1 = 1st IE

A+(g) A2+(g) + e- ; E = IE2 = 2nd IE

Always positive. Why?

Trends in First IEincreases

decreases

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

IE1 Values for First 20 Elements (Problem 4)

Why is IE1(N) > IE1(O)?

O: 1s22s22p4

N: 1s22s22p3

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: 1s22s2 ; B: 1s22s22p1

Elements with filled shells (noble gases) Elements with filled subshells

IEBe > IEB

Elements with half-filled subshells IEN > IEO