Polyatomic Molecules

Question 1

Molecules with 2 electron pairs around central atom?

Answer 1

AX2 Linear 180 degrees

Question 2

Molecules with 3 electron pairs around central atom?

Answer 2

AX3 Trigonal planar 120 degrees

Question 3

Molecules with 4 electron pairs around central atom?

Answer 3

AX4 Tetrahedral 109.5 degrees

Question 4

Molecules with 5 electron pairs around central atom?

Answer 4

AX5 Trigonal bipyramid 120 and 90 degrees

Question 5

Molecules with 6 electron pairs around central atom?

Answer 5

AX6 Octahedral 90 degrees

Question 6

Molecules with 7 electron pairs around central atom?

Answer 6

AX7 Pentagonal bipyramidal 72 and 90 degrees

Question 7

Three bonding pairs one lone pair?

Answer 7

AX3E Trigonal pyramidal 107.8 degrees

Question 8

Two bonding pairs one lone pair?

Answer 8

AX2E Bent 95 degrees

Question 9

Four bonding pairs one lone pair?

Answer 9

AX4E See saw/sawhorse 103 degrees

Question 10

Three bonding pairs two lone pairs?

Answer 10

AX3E2 T shaped 87 degrees

Question 11

Five bonding pairs one lone pair?

Answer 11

AX5E Square based pyramid 85 degrees

Question 12

Four bonding pairs two lone pairs?

Answer 12

AX4E2 Square planar less than 90 degrees

Question 13

Two bonding pairs two lone pairs?

Answer 13

AX2E2 V shapes 104.5 degrees

Question 14

One bonding pair three lone pairs?

Answer 14

AXE3 Linear

Question 15

Hard acids?

Answer 15

If a molecules or ion has largely electrostatic, ionic interactions, small or highly charged centre, it will be classed as a hard acid or base, more electronegative an atom the harder it will be
Hard acids prefer to complex with hard bases H+ Mg2+ BF3 Ti4+ Mn+ Fe3+

Question 16

Hard bases?

Answer 16

F-, OH2, NH3, O2-

Question 17

Soft acids?

Answer 17

Largely covalent interactions soft acids or bases, soft-soft interactions are more orbital based and a soft acid would prefer to complex with soft bases
Cu+ Pd2+ Hd2+ Pt2+

Question 18

Soft bases?

Answer 18

Br- PH3 BH3 I- CN-

Question 19

Chelate effect?

Answer 19

A complex containing 5 or 6 membered rings is more stable than the one without the chelate ring, for example complexes with 3 chelate rings are approximately 2 times more stable than those with six mono dentate ligands, this is a combined kinetic and thermodynamic effect since it is tropically driven. the increase in disorder in the reaction involving the chelate lianas is positive and means this reaction is highly favoured

Question 20

Kf?

Answer 20

If Kf is large the ligand binds more tightly to the metal centre than H2O
If Kf is small the ligands bind less tightly than H2O

Question 21

Delta isomers?

Answer 21

Right hand screw

Question 22

Lambda isomers?

Answer 22

Left hand screw

Question 23

Ligand?

Answer 23

Group or atom that gives a metal centre a pair of electrons, normally through an available lone pair

Question 24

Order of repulsion?

Answer 24

LP-LP > LP-DB > LP-SB > DB-DB > DB-SB > SB-SB

Question 25

Ligands and charge?

Answer 25

en neutral
pn neutral
biped neutral 
phen neutral
[acac]- 1 minus
[ox]2- 2 minus
dien neutral 
terry neutral 
[edta]4- 4 minus

Question 26

Hard ligands?

Answer 26

Small electronegative donor atoms, hard metals carry a high charge or have high charge density, bonding between hard metals and hard ligands has a high degree of ionic character

Question 27

Soft ligands?

Answer 27

Soft metals have a lower charge and tend to be larger and more polarisable, ligands that have larger more polarisable donor atoms, the bonding between soft metals and soft ligands has a high degree of covalent character

Question 28

Examples of hard metals?

Answer 28

Ti4+ VO2+ Sc3+ Cr3+ Fe3+ Co3+ Cr2+ Mn2+

Question 29

Examples of intermediate metals?

Answer 29

Fe2+, Co2+, Ni2+, Cu2+, Zn2+, Rh3+, Ir3+, Ru3+, Os3+

Question 30

Examples of soft metals?

Answer 30

Cu+, Ag+, Au+, Pd2+, Cd2+, Pt2+, Hg2+

Question 31

Examples of hard ligands?

Answer 31

F-, Cl-, OH-, O2-, NO3-, SO42-, CO32-, H2O, NH3

Question 32

Examples of intermediate ligands?

Answer 32

Br-, N3-, NCS-, NO2-, SO32-

Question 33

Examples of soft ligands?

Answer 33

H-, R-, CN-, I-, SCN-, CO, PR3, SR2