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Chemistry 90% > Molecular structure/ Photochemistry > Flashcards

Molecular structure/ Photochemistry Flashcards

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1
Q

Why e- promotion?

A

To equally share the e- at the valence shell to be more stable. Easier to single fill the orbitals than pair up the e-

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2
Q

How to identify the molecular structure arrangement with using the lewis structure

A
  1. Count all the valence e-
  2. Count e- pairs
  3. Arrange atoms and identify the central atom (the atom that has the lowest ionisation energy)
  4. Locate bonding pair of e-
  5. Complete Octets (s2p6) and Duplets (s2 only for hydrogen as it has 1 energy shell only)
  6. Apply VSEPR theory
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3
Q

Lewis structure gives _______ of molecule

A

e- arrangement only

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4
Q

what gives the molecular structure/shape

A 
VSEPR 
Valence
Shell
Electron
Pair
Repulsion
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5
Q

Molecule shape alters, depend on__________

A

VSEPR theory

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6
Q

AX(2)E(1)

A

sp^2 (2 bonding pair e-, 1 lone pair e-) – Bent

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7
Q

AX(6)

A

sp^3d^2 (6 bonding pair e- ) – Octahedral

e.g. SF(6)

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8
Q

AX(5)

A

sp^3d (5 bonding pair e-) - Trigonal bipyramidal

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9
Q

AX(4)

A

sp^3 (4 bonding pair e-) – Tetrahedral

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10
Q

AX(3)

A

sp^2 ( 2 bonding pair e-) - Trigonal planar

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11
Q

AX(2)

A

sp (1 bonding pair e-) – linear

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12
Q

List different types of structure arrangement

A

AXn ; AX(n-1)E(1) ; AX(n-2)E(2)
A- Central atom
X- Bonding e- pair
E- Lone e- pair

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13
Q

Hybridsation happens because ___________

A

valence e- get promotion and energy re- arranged in order for the atom to become more stable.
(2s & 2p energy difference is small, doesn’t take much for energy re-arrangement take place)

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14
Q

When Hybridsation has to happen ?

A

Before molecular bonding. It is the overlap of two different energy valence orbitals of the same atom e.g. orbital s – p

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15
Q

If 2 e- of Carbon hybridise, it gives ?

A

it will give sp + 2p > 1 sigma, 2 pi bond > which gives the atom a triple bond i.e., alkyne

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16
Q

If 3 e- of Carbon hybridise, it gives?

A

it will give sp2 + 1p > 1 sigma, 1 pi bond > which gives the atom a double bond i.e., alkene

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17
Q

If 4 e- of Carbon hybridise, it gives?

A

it will gives sp3 > a sigma bond > which gives the atom single bond i.e., alkane

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18
Q

Intranuclear distance

A

The distance between two nuclei in a molecule = Σ(a) - Σ(r)

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19
Q

Quantum

A

energy amount balancing out the energy level

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20
Q

Energy __________ when bond break

Energy __________ when bond formed

A
  • Needed

- Released

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21
Q

What affects the bond length and bond strength

A
  • No of p+
  • No of e-
  • No of energy shell
  • Atomic radius
  • No of shared e-
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22
Q

The greater the bonding energy, the _________bond strength, the more_______the molecule is

A

the stronger bond strength; the more stable stable the molecule is

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23
Q

Anti- bonding orbitals has _________ energy than bonding orbitals

A

more energy

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24
Q

Homonuclear molecule

A

molecules composed of one type of element

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25
Q

Degenerate orbitals

A

Orbitals with the same energy level

E.g. p orbital > px / py / pz

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26
Q

How many e - on each orbitals

A

2 e-

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27
Q

how many e- on each sub level

A

s -2
p - 6
d - 10
f - 14

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28
Q

how many e- on each sub shell

A

1st - 2
2nd - 8
3rd - 18
4th - 32

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29
Q

why He(2) doesn’t exist?

A

because he already has a full outer shell, it doesn’t need boning to become stable

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30
Q

The bonding orbital energy level sequence depends on the ___________

A

element combination

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31
Q

HOMO/ LUMO theory

A

The energy difference between Highest Occupied Molecular Orbitals & Lowest Unoccupied Molecular Orbitals

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32
Q

π bonding energy is always greater than σ bonding, because__________

A

π bonding is p - p (side - side) orbitals overlap

σ bonding is s- s / s-p / p-p (head - head) orbitals overlap

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33
Q

lone pair e- has more energy than bonding pair e- , because_______

A

bonding pair e- are fixed ; lone pair e- are free to spin around

34
Q

Based on the HOMO/LUMO theory, e- transition can be ? and what is needed for the transition ?

A 
σ - σ *
π - π *
n - π
n - σ *
Energy
35
Q

Bond length

A

Distance between the 2 nucleus as a stable structure and bond formed

36
Q

Rules for bonding orbitals

A

No of combining atomic orbitals = no of molecular orbitals

But may not be the same type of orbitals

37
Q

Hybridisation is based on ____

A
  • electronic configuration
  • Octet rule
  • Ability of non- metal
  • Share e- to obey the Octet rule
38
Q

Sigma bond

Pi bond

A
  • Overlap of orbitals s – s / s- p / p – p, head to head gives sigma bond
  • Overlap of orbitals p – p, side to side gives pi bond.
39
Q

Lewis acid

A

Lone pair acceptor e.g. BF(3)

40
Q

Hybridisation gives ___________

A

~ re-arrangement e-
~ mixing of orbitals
~ mixing of properties

41
Q

Hybrid bond is

A

an atomic bond

42
Q

Hybrid orbital is

A

an atomic orbital

43
Q

Evidence of hybridisation

A

The molecular shape

44
Q

The molecular shape has impact on

A

molecular behaviours

45
Q

Lewis base

A

lone pair donor e.g. NH(3)

46
Q

For complex chemistry, Ligand will ________ lone pair e- ; Transmetal will ________ lone pair e-

A
  • donate

- accept

47
Q

Complex chemistry

A

small molecules stick together to form complex molecule

48
Q

Complex bond

A

Use of Lewis Acid/ Base come together to give dative bond

49
Q

hierarchy of repulsion of e-

A

Non- bonding e- Non- bonding e-
bonding e- Non- bonding e-
bonding e- bonding e-

50
Q

What can also act as Ligands

A

Polyatomic ions and simple ions

51
Q

monodentate ligand

A

one pair of e- donated

52
Q

polydentate ligand

A

more than one pair of e- donated

53
Q

Alloy

A
  • mixture composed of different metal elements
  • e.g. Steel > iron and some other metal
  • allowed because of similar atomic radius of d elements
54
Q

Magnetism of d element

A

Fully magnetic - iron / nickle/ cobalt
Partial magnetic
Dimagnetic

55
Q

Polyatomic cation & simple cation that have
the same charge will behave __________

Polyatomic cation & simple cation that have the different charges will behave __________

A
  • behave the same when in solution

- behave different yet similar in the solutionW

56
Q

Wavelength = energy

Shorter the λ, _____ the energy ; longer λ, ________ the energy

A

Shorter > higher E

Longer > lower E

57
Q

Refer to the e- transition, increase in internal energy = ?

Decrease in internal energy = ?

A 
increase = absorption
decrease = Emission
58
Q

If it is white, ?

If it’s dark, ?

A

No interaction if it’s white, all light bounce back

If it’s dark, light is absorbed

59
Q

e- transition

A

~ e- energy jumping from low energy orbital to high energy orbital
~ splitting of energy at d- orbital
~ d orbital normal degenerate

60
Q

Crest
Trough
amplitude
Wavelength

A
  • top of the curve
  • bottom of the curve
  • line the tip of curve
  • distance between a crest and the next / a trough to the next
61
Q

Different wavelength

A

Cosmic rays > Gamma rays > X rays (bonds of all 3 will break because of the high energy)
> ultraviolet >Visible > infrared > Microwave > Radio

62
Q

Visible spectrum

A

400 nm - Violet > Blue > Green > Yellow > Orange > Red > Purple - 800nm

63
Q

Within the electric field, how will electron behaves?

A
  • Bond breaking & ionisation (X rays)
  • Electronic excitation (Visible & ultraviolet)
  • Vibration (infrared)
  • Rotation (microwave)
64
Q

Self sustaining free radical cycle: 3 steps ?

A

~ Initiation – photodissociation / photolysis
~ Propagation
~ Termination

65
Q

Summary of the important reactions for formation of Smog

A

NO2 absorbed solar energy > NO + O

  • -> NO reacts with O3 > NO2+
  • -> NO2 react further with hydrocarbon free radicals > PAN, aldehydes and other smog components
  • -> O reacts with O2 yield Ozone molecule, O3
  • –> O3 + OH+ > highly reactive hydrocarbon free radicals

OH+ reacts with other species > chain reactions

66
Q

polyatomic ions

A 
- ions that contains more than one type of 
elements
- Resonance structure
- All atoms covalent bonded
- Delocalisation of charge
67
Q

Photochemistry

A

Energy taken in and transfer e- to higher energy. Energy given up as light and the lowering of energy
(Excess energy is get rid of by releasing light)

68
Q

Light

A

Electromagnetic radiation , energy travelling in waves

69
Q

All light travels in ___________, different types of light has ____________

A

travels in a fix pattern

has a specific wave length

70
Q

Speed of light formula / Energy of wave length formula

A

1) C = v. λ
2) E= h. v
–> E α 1/ λ
[C= speed of light v = frequency λ = wavelength E = energy h= Plank’s Constant]

71
Q

longer λ more likely to ________

A

be bounced off and scatter

72
Q

What would affects the colour change

A

pH changes / e - rearrangement / changing the bonding between / electronic structure change / energy absorbed change

73
Q

Octet rules are not always followed, why?

A

Full filled valence shell & 1/2 filled valence shell are most stable
For example most d elements can lose variable no of e- (Oxidation state) Most possibly happen in the middle of d- block, and decrease as go towards s/ p block

74
Q

Oxidation state

A

most d elements can lose variable no of e- to achieve full valence shell or half full valence shell to be more stable.

75
Q

D orbital electrons

A

dz2 dx2-y2 dxy dyz dxz

76
Q

D orbital splitting

A

dz2 dx2-y2
| (Octahedral)
dxy dyz dxz

dxy dyz dxz
| (Tetahedral)
dz2 dx2-y2

77
Q

D block element (Trans metal)

A
  • Lattice structure
  • Alloy
  • Magnetic properties
  • Redox chemistry
  • Ability of the same element to form different colour solutions < orbitals can be split ; Light can come in as energy to promote e-
  • Ligand: something that bind with metals
78
Q

Co- ordinate ions

A

a form of polyatomic ions with d- block metal in the central with a ligand bond to it with a covalent bond

79
Q

Example of a natural molecule to become ligand

A

Water

80
Q

Free radical

A

It is with un- paired e- ; extremely reactive and seek to pair up e-
Covalent bonds from the free radical are break & reformed
It is related to cancer and antioxidant interaction

Chemistry 90% (7 decks)

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