Lecture 2511/02/05 Harvard Professor Dimitar Sasselov talk about discovering new extra-solar planets...
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Transcript of Lecture 2511/02/05 Harvard Professor Dimitar Sasselov talk about discovering new extra-solar planets...
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
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*
Isoelectronic(same electron configuration)
Ne: 1s22s22p6
F: 1s22s22p5
F-: 1s22s22p6
Na: 1s22s22p63s1
Na+: 1s22s22p6
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
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-