Lecture 25 11/02/05

Harvard Professor Dimitar Sasselovtalk about discovering new extra-solar planetsToday 5:30 Refreshments at 5:00

TSB 006

Ion ConfigurationsIon Configurations

Ions: Anions: negatively charged ions --- gain electrons Cations: positively charged ions --- lose electrons

Electrons are gained or lost from subshell of highest n

P: [Ne] 3s2 3p3 P3+: [Ne] 3s2 3p0

1s

2s

3s3p

2p

1s

2s

3s3p

2p

Ion ConfigurationsIon Configurations

4s 3d 3d4s

Fe Fe2+

3d4s

Fe3+

For transition metals, remove highest ns electrons first and then (n - 1) electrons.

Fe: [Ar] 4s2 3d6 Fe2+ : [Ar] 4s0 3d6 Fe3+ : [Ar] 4s0 3d5

Diamagnetic:

Not attracted to a magnetic field

All the electrons are paired

Paramagnetic:

Attracted to a magnetic field

Has unpaired electrons

Paramagnetic Ferromagnetic

Z* is the effective nuclear charge experienced by the outermost electrons. Based on 2 things

Positive charge in nucleus Screening from inner shell electrons

Explains why E(2s) < E(2p)Z* increases across a period owing to incomplete shielding by inner electrons.Estimate Z* by --> [ Z - (no. inner electrons) ]Charge felt by 2s e- in

Li Z* = 3 - 2 = 1 Be Z* = 4 - 2 = 2 B Z* = 5 - 2 = 3

Effective Nuclear Charge, Z*

Give the electron configurations for Cu, Cu+, Cu+2.

Are any of these paramagnetic?

Isoelectronic(same electron configuration)

Ne: 1s22s22p6

F: 1s22s22p5

F-: 1s22s22p6

Na: 1s22s22p63s1

Na+: 1s22s22p6

Which of the following species are isolectronic with Ar?Na+

KK+

Cl-

Atomic SizeCan measure atomic radii by experimentally measuring distance between atomic centers C radius: 77 pm Cl radius: 99 pm

Size determined by: Electron shell

Higher n larger size

Effective nuclear charge Higher Z* smaller size

Trends in Ion SizesTrends in Ion Sizes

Sizes of Transition ElementsSizes of Transition Elements

3d subshell is inside the 4s subshell.

4s electrons feel a more or less constant Z*.

Sizes stay about the same and chemistries are similar!

Ionization EnergyIonization Energy

Energy required to remove an electron from an atom in the gas phase.

Mg (g) + 738 kJ ---> Mg+ (g) + e-

Mg+ (g) + 1451 kJ ---> Mg2+ (g) + e-

Mg2+ (g) + 7733 kJ ---> Mg3+ (g) + e-

Trends in Ionization EnergyTrends in Ionization Energy

1 3 5 7 9 11 13 15 17 19 21 23 25 27 29 31 33 350

500

1000

1500

2000

2500

1st Ionization energy (kJ/mol)

Atomic NumberH Li Na K

HeNe

ArKr

IE increases across a period because Z* increases.

Metals lose electrons more easily than nonmetals.