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Inorganic Chemistry > Molecular shapes and orbitals > Flashcards

Molecular shapes and orbitals Flashcards

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1
Q

chemical bond

A

link between 2 atoms

forms if resulting arrangement of the nuclei and their e- has lower energy than total energy of separate atoms (i.e. more energetically favourable)

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2
Q

name of group 6 elements

A

chalcogens

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3
Q

types of bonding

A
  1. ionic
  2. covalent
  3. metallic
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4
Q

types of bonding models

A
  1. valence bond theory (localised)
  2. molecular orbital theory (delocalised)
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5
Q

why does hypervalence exist?

A

due to free d-orbitals

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6
Q

dative bond

A

one atom donating a lone pair of e- in one orbital into a vacant orbital on another atom

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7
Q

resonance

A

e- in molecules aren’t always localised to specific bonds

Lewis structure preducts 1 double bond and 2 single bonds (actually both lengths are equal + charges = shared)

used to explain that actual structure is a hybrid of all possible forms

charge = delocalised

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8
Q

which position would double bonds occupy - axial or equatorial?

A

equatorial - minimises space and repulsion

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9
Q

which occupy more space - electronegative sub. or electropositive sub.?

A

bonded pairs to electropositive substituents

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10
Q

stereochemically inactive lone pair

A

occurs if l.p. is in an s-orbital and is evenly distributed around the molecule (∴ has no impact on shape)

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11
Q

possible structures with 5 valence e-

A
  1. trigonal bipyramidal - more likely
  2. square based pyramid
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12
Q

fluxional

A

isomers that can undergo dynamic interchanges between atoms in symmetry-equivalent positions

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13
Q

which position do lone pairs always occupy?

A

equatorial

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14
Q

Berry pseudorotation

A

the process which scrambles axial and equatorial ligands on a trigonal bipyramidal

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15
Q

how to prevent flux between molecules?

A

reaction @ low temp. (freeze it out)

product = only thermodynamic one (might not be most kinetically stable one)

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16
Q

VSEPR - single/multiple bonds

A

indistinguishable

multiple bond treated as single bond of higher e- density

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17
Q

electronegativity + effect of bond polarity on BP/LP in orbital arrangements

A

more polar bonds concentrate e- density at one atom or the other

also influence e- repulsion

e.g. e- density closer to F than Cl (more electronegative) - make it easier to push bonding pairs together to maximise BP-LP repulsion

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18
Q

order of repulsion power

A

LP-LP (strongest)

LP - double bond

LP - single bond

double bond-double bond

double bond-single bond

single bond-single bond (weakest)

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19
Q

rotation by 180°

A

C2 rotation

20
Q

rotation by 120°

A

C3 rotation

21
Q

rotation by 60°

A

C4 rotation

22
Q

rotation by 90°

A

C6 rotation

23
Q

transition metal

A

metal in an element in which the valence e- = d electrons

24
Q

“d-block” or “transitional”

A

elements with partially full or full d-shells

25
Q

Haemoglobin

A

O2 transport

contains dicationic Fe2+ metal centre surrounded by nitrogen-based ligand (= haem ligand)

complex binds via l.p. on oxygen to form saturated coordination Fe2+ complex
CO and CN- are good ligands for Hb and compete for Fe2+ site (∴ toxic)

26
Q

ligand

A

group or atom that gives metal centre pair of e-, normally available via l.p.

metal ion = Lewis acid (acceptor)

ligand = Lewis base (donator)

27
Q

monodentate ligand

A

only binds to metal through 1 l.p. of electrons

28
Q

polydentate ligand

A

binds to metal via 2 or more lone pairs

29
Q

shape of transition metals

A

d-block elements have 9 orbitals available - VSEPR doesn’t work

shape dictated by no. of coordinated atoms around metal

30
Q

chiral molecules

A

non-superimposable mirror images (related by enantiomers)

31
Q

coordination isomers

A

ligands attached to each of the 2 metals are different

32
Q

linkage isomers

A

involve ambidentate ligands

M-NCS or M-SCN

33
Q

polymerisation isomers

A

same forumla, different molar mass (same empirical formula)

34
Q

stability constant and hard/soft acids + bases

A

if Kf is large = ligand binds more tightly to metal centre than H2O

if Kf is small = ligand binds less tightly to metal centre than H2O

35
Q

chelate effect

A

complex containing one or more 5/6 membered chelate rings is more stable (stability constant = larger) than one without chelate ring

due to thermodynamics

choose polydentate ligand over monodentate
larger log(β) value

36
Q

chelate effect + ring size

A

decreases as ring size increases
chance of “dangling arm” binding to metal becomes smaller

4 membered ring = 5-membered ring > 6-membered ring > 7-membered ring

37
Q

early transition metals (Ti, V, Cr) + halides

A

complexing strength = F-&raquo_space; Cl- > Br- > I-

38
Q

later transition metals + halides

A

complexing strength = I-&raquo_space; Br- > Cl- > F-

39
Q

hard cations

A

high density charge

less polarisable

form more stable complexes with hard ligands

40
Q

soft cations

A

low density charge

more polarisable

form more stable complexes with soft ligands

41
Q

hard acids

A

prefer to complex with hard bases

42
Q

soft acids

A

prefer to complex with soft bases

43
Q

do hard-hard or soft-soft interactions have greater electrostatic/ionic contribution?

A

hard-hard

44
Q

do hard-hard or soft-soft interactions have greater orbital/covalent interactions (overlap)?

A

soft-soft

45
Q

trend in hardness down a group

A

decreases

orbitals get larger + more diffuse

electronegativity decreases

46
Q

influence of electronegativity on hardness/softness of an element

A

more electronegative = harder (less polarisable)

47
Q

influence of size on hardness/softness of an element

A

smaller element/ion = harder

Inorganic Chemistry (15 decks)

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