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Chemistry 90% > Molecular structure/ Photochemistry > Flashcards

Molecular structure/ Photochemistry Flashcards

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
Degenerate orbitals
Orbitals with the same energy level | E.g. p orbital > px / py / pz
26
How many e - on each orbitals
2 e-
27
how many e- on each sub level
s -2 p - 6 d - 10 f - 14
28
how many e- on each sub shell
1st - 2 2nd - 8 3rd - 18 4th - 32
29
why He(2) doesn't exist?
because he already has a full outer shell, it doesn't need boning to become stable
30
The bonding orbital energy level sequence depends on the ___________
element combination
31
HOMO/ LUMO theory
The energy difference between Highest Occupied Molecular Orbitals & Lowest Unoccupied Molecular Orbitals
32
π bonding energy is always greater than σ bonding, because__________
π bonding is p - p (side - side) orbitals overlap | σ bonding is s- s / s-p / p-p (head - head) orbitals overlap
33
lone pair e- has more energy than bonding pair e- , because_______
bonding pair e- are fixed ; lone pair e- are free to spin around
34
Based on the HOMO/LUMO theory, e- transition can be ? and what is needed for the transition ?
``` σ - σ * π - π * n - π n - σ * Energy ```
35
Bond length
Distance between the 2 nucleus as a stable structure and bond formed
36
Rules for bonding orbitals
No of combining atomic orbitals = no of molecular orbitals | But may not be the same type of orbitals
37
Hybridisation is based on ____
- electronic configuration - Octet rule - Ability of non- metal - Share e- to obey the Octet rule
38
Sigma bond | Pi bond
- 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
Lewis acid
Lone pair acceptor e.g. BF(3)
40
Hybridisation gives ___________
~ re-arrangement e- ~ mixing of orbitals ~ mixing of properties
41
Hybrid bond is
an atomic bond
42
Hybrid orbital is
an atomic orbital
43
Evidence of hybridisation
The molecular shape
44
The molecular shape has impact on
molecular behaviours
45
Lewis base
lone pair donor e.g. NH(3)
46
For complex chemistry, Ligand will ________ lone pair e- ; Transmetal will ________ lone pair e-
- donate | - accept
47
Complex chemistry
small molecules stick together to form complex molecule
48
Complex bond
Use of Lewis Acid/ Base come together to give dative bond
49
hierarchy of repulsion of e-
Non- bonding e- Non- bonding e- bonding e- Non- bonding e- bonding e- bonding e-
50
What can also act as Ligands
Polyatomic ions and simple ions
51
monodentate ligand
one pair of e- donated
52
polydentate ligand
more than one pair of e- donated
53
Alloy
- mixture composed of different metal elements - e.g. Steel > iron and some other metal - allowed because of similar atomic radius of d elements
54
Magnetism of d element
Fully magnetic - iron / nickle/ cobalt Partial magnetic Dimagnetic
55
Polyatomic cation & simple cation that have the same charge will behave __________ Polyatomic cation & simple cation that have the different charges will behave __________
- behave the same when in solution | - behave different yet similar in the solutionW
56
Wavelength = energy | Shorter the λ, _____ the energy ; longer λ, ________ the energy
Shorter > higher E Longer > lower E
57
Refer to the e- transition, increase in internal energy = ? | Decrease in internal energy = ?
``` increase = absorption decrease = Emission ```
58
If it is white, ? | If it's dark, ?
No interaction if it's white, all light bounce back | If it's dark, light is absorbed
59
e- transition
~ e- energy jumping from low energy orbital to high energy orbital ~ splitting of energy at d- orbital ~ d orbital normal degenerate
60
Crest Trough amplitude Wavelength
- 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
Different wavelength
Cosmic rays > Gamma rays > X rays (bonds of all 3 will break because of the high energy) > ultraviolet >Visible > infrared > Microwave > Radio
62
Visible spectrum
400 nm - Violet > Blue > Green > Yellow > Orange > Red > Purple - 800nm
63
Within the electric field, how will electron behaves?
- Bond breaking & ionisation (X rays) - Electronic excitation (Visible & ultraviolet) - Vibration (infrared) - Rotation (microwave)
64
Self sustaining free radical cycle: 3 steps ?
~ Initiation – photodissociation / photolysis ~ Propagation ~ Termination
65
Summary of the important reactions for formation of Smog
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
polyatomic ions
``` - ions that contains more than one type of elements - Resonance structure - All atoms covalent bonded - Delocalisation of charge ```
67
Photochemistry
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
Light
Electromagnetic radiation , energy travelling in waves
69
All light travels in ___________, different types of light has ____________
travels in a fix pattern | has a specific wave length
70
Speed of light formula / Energy of wave length formula
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
longer λ more likely to ________
be bounced off and scatter
72
What would affects the colour change
pH changes / e - rearrangement / changing the bonding between / electronic structure change / energy absorbed change
73
Octet rules are not always followed, why?
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
Oxidation state
most d elements can lose variable no of e- to achieve full valence shell or half full valence shell to be more stable.
75
D orbital electrons
dz2 dx2-y2 dxy dyz dxz
76
D orbital splitting
dz2 dx2-y2 | (Octahedral) dxy dyz dxz dxy dyz dxz | (Tetahedral) dz2 dx2-y2
77
D block element (Trans metal)
- 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
Co- ordinate ions
a form of polyatomic ions with d- block metal in the central with a ligand bond to it with a covalent bond
79
Example of a natural molecule to become ligand
Water
80
Free radical
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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