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H2 Chemistry > 03 + 08 Chemical Bonding I + II > Flashcards

03 + 08 Chemical Bonding I + II Flashcards

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1
Q

Ionic Lattice

Structure

A
  1. ions held in fixed positions in an orderly arrangement
  2. attraction between the oppositely-charged ions is a maximum
  3. repulsion between similarly-charged ions is a minimum
  4. bonds are non-directional i.e. attracts an oppositely-charged ion in all directions without a preferred orientation
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2
Q

Ionic Bond, IB

Definition

A

An electrostatic attraction between cations and anions i.e oppositely-charged ions.

IBs are non-directional

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3
Q

Lattice Energy, ΔHlatt/ LE

Formula

A

|LE| = |q+ x q-/ r+ + r-|

where,
q+ = charge on cation
q- = charge on anion
r+ = radius of cation
r- = radius of anion

↑|LE|, ↑ strength of IB

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4
Q

Ionic Bond

Factor(s)

A
  1. Higher Charge: ↑ Electrostatic Attraction
  2. Smaller Radius: ↓ Inter-ionic Distance
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5
Q

Ionic Compounds

Physical Properties

A
  1. High melting & boiling point
    a. ↑ amounts of energy required to break the bonds between oppositely-charged ions for melting/ boiling
  2. Generally soluble in polar solvents eg. H2O and vice versa
  3. Conducts electricity in (ℓ) & (aq) states
    a. Ions are mobile and can act as mobile charge carriers
  4. Hard & brittle
    a. Slight displacement along a cleavage planes brings ions of like charges opposite each other
    b. Strong attraction between the planes becomes strong repulsion
    c. Plane shatters
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6
Q

Giant Molecular Lattice

Structure & Properties of Diamond

A
  1. High melting point & insolubility in H2O/ other solvents
    a. sp3-hybridised C
    b. Covalently bond to 4 other C atoms
    c. Tetrahedral arrangement
    d. Strong and rigid structure
  2. Electrical insulator
    a. Made up of neutral atoms
    b. Lack of mobile charge carries i.e delocalised e-
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7
Q

Giant Molecular Lattice

Structure & Properties of Graphite

A
  1. Layer structure & planes of interconnected hexagonal rings of C
    a. sp2-hybridised C
    b. Forms 3 σ bonds with 3 other C atoms
    c. Trigonal planar shape about C
    d. BA of 120°
  2. Electrical conductor
    a. Unhybridised p-orbital, containing single e-
    b. Continuous overlap with p-orbital of immediate neighbours
    c. Extended π-e- cloud
    d. Delocalisation of π e- over whole layer
    e. Electricity conducted parallel to the layers
  3. High melting point: Used as crucibles for molten metals and reentry nose cones of rockets
    a. Strong covalent bonds within each layer
    b. ↑ energy is required to overcome strong forces of attraction
  4. Soft: Used in pencils and lubricants
    a. Weak id-id interactions between each layer
    b. Layers glide over each other
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8
Q

Giant Molecular Lattice

Structure & Properties of Silicon Dioxide, Quartz

A
  1. Hard & insoluble in all solvents
    a. Covalent bonds between Si & 4 O/ O & 2 Si
    b. Tetrahedral arrangement
    c. Rigid 3D structure due to strong covalent bonds
  2. Electrical insulator
    a. Made of atoms
    b. Lack of mobile charge carriers i.e delocalised e-
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9
Q

Simple Molecular Lattice

Structure & Properties

A
  1. Low melting point
    a. Attract each other through weak id-id interactions
  2. Soluble in non-polar solvents
    a. Solute and solvent have the same type of intermolecular interactions, id-id interactions
  3. Electrical insulator unless ionisation in (aq) occurs
    a. Lack of mobile charge carriers
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10
Q

Metallic Lattice

Structure

A
  1. Rigid lattice of cations
  2. ‘Sea’ of delocalised e- = displaced valence e-

e- belong to the crystal lattice as a whole instead of a particular cation

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11
Q

Metallic Bond, MB

Definition

A

The electrostatic attraction between a lattice of cations and delocalised electrons.

MBs are non-directional

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12
Q

Metallic Bonds, MB

Factor(s)

A
  1. Number of VE available
    a. ↑ VE
    b. ↑ strength of MB
  2. Charge of cation
    a. ↑ charge
    b. ↑ strength of MB
  3. Size of cation
    a. ↓ size
    b. ↑ charge density
    c. ↑ electrostatic attraction for the delocalised e-
    d. ↑ strength of MB
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13
Q

Metals

Physical Properties

A
  1. High electrical conductivity in all states
    a. Presence of mobile charge carries i.e delocalised e-
    b. Flow toward the positive terminal as long as potential difference is applied to the end of a metal
  2. Good thermal conductivity
    a. e- take in thermal energy
    b. e- move faster and more randomly
    c. collide with other e-
    d. energy is passed along
  3. Malleable i.e beaten into shape & ductile i.e drawn into a wire
    a. Cations can glide over another easily without breaking the MB
  4. High density
    a. Cations are closely-packed
  5. High melting & boiling points
    a. Strong MB
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14
Q

Drawing dot-and-cross

Polyatomic Ions

A

For cations:
Assign charge to less electronegative atoms
For anions:
Assign charge to more electronegative atoms

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15
Q

Covalent Bond

Definition

A

The electrostatic attraction between the shared pair of electrons and the positively-charged nuclei.

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16
Q

Dative Covalent Bond

aka Co-ordinate Bond

A

Shared pair of electrons is provided by only one of the bonding atoms.

Representation: → from the donor atom to acceptor atom

17
Q

Dative Covalent Bond

Conditions

aka Co-ordinate Bond

A

Donor atom: Lone pair of e-
Acceptor atom: Vacant, low-lying orbital

Low-lying orbital must be in the same sub-shell or ES as those occupied

18
Q

Drawing dot-and-cross

Covalent Compounds

A
  1. Determine the number of VE of each other.
  2. Identify the central atom which is normally the least EN atom.
  3. Arrange the peripheral atoms.
  4. Determine the bonds between the central and peripheral atoms in order to achieve duplet/ octet structure where possible.
  5. Check that e- on every atom correspond to group number.
  6. Draw any remaining e- as lone pairs.

For elements in Period 3 and beyond, molecules can have an expanded octet.

19
Q

VSEPR Theory

Basis

A
  1. e- pairs around the central atom of a molecule are arranged as far apart as possible in space, minimising mutual repulsion.
  2. LP-LP repulsion > LP-Bond Pair > BP-BP repulsion
20
Q

VSEPR Theory

2 Electron Density Regions

A

Electron-Pair Geometry, EPG : Linear

O Lone Pairs, LP;
Shape: Linear
Bond Angle, BA: 180°

For LP, -2°

21
Q

VSEPR Theory

3 Electron Density Regions

A

EPG : Trigonal Planar

O LP:
Shape: Trigonal Planar
BA: 120°

1 LP:
Shape: Bent
BA: <120°

For LP, -2°

22
Q

VSEPR Theory

4 Electron Density Regions

A

EPG: Tetrahedral

0 LP:
Shape: Tetrahedral
BA: 109.5°

1 LP:
Shape: Trigonal Pyramidal
BA: ~107°

2 LP:
Shape: Bent
BA: ~105°

For LP, -2°

23
Q

VSEPR Theory

5 Electron Density Regions

A

EPG: Trigonal Bipyramidal

0 LP:
Shape: Trigonal Bipyramidal
BA: 90°/ 120°

1 LP:
Shape: See-saw
BA: N.A.

2 LP:
Shape: T-shape
BA: 90°

3 LP:
Shape: Linear
BA: 180°

For LP, -2°

24
Q

VSEPR Theory

6 Electron Density Regions

A

EPG: Octahedral

0 LP:
Shape: Octahedral
BA: 90°

1 LP:
Shape: Square Bipyramidal
BA: < 90°

2 LP:
Shape: Square Planar
BA: 90°

For LP, -2°

25
Q

VSEPR Theory

Bond Angle Modification

A
  1. e- pair-e- pair repulsion
    a. Closer e--pair is to the central atom, ↑ repulsion
    b. About the same central atom, LP exerts ↑ repulsion than BP as LP is attracted to 1 nucleus and is closer to the central atoms while BP is attracted to 2 nuclei.
    c. As no. of LP ↑, BA deviates ↑ greatly from the predicted angle.
  2. Effect of EN of central atom on BA
    a. ↑ EN the central atom
    b. BPs are drawn closer to itself
    c. BP e- are nearer to the nucleus
    d. ↑ repulsion is exerted
    e. BA ↑
26
Q

Instantaneous dipole-induced dipole, id-id, interactions

Formation & Factor(s)

A

Formation:
1. e- density of a particle can be asymmetrical
2. Instantaneous dipole formed
3. Dipole induced in neighbouring particle
4. Attraction occurs

Factor(s):
1. Electron Cloud Size = Mr
a. ↑ e- cloud
b. ↑ easily polarised
c. ↑ ease of formation of id-id interactions
d. ↑ strength of id-id interactions
2. Surface area for molecular interaction eg. branched HC vs straight-chain HC
a. ↓ branching
b. ↑ surface area for intermolecular interactions
c. ↑ strength of id-id interactions
d. straight-chain molecules have a ↑ boiling point than branched isomers

Use the donut vs. baguette analogy for point 2

27
Q

Permanent dipole-permanent dipole, pd-pd interactions

Factor(s)

A

Polarity of the molecule

28
Q

Permanent dipole-permanent dipole, pd-pd interactions

Formation & Criteria of Hydrogen Bond

A

Formation:
1. > EN F/ O/ N atom causes H to have a ↑ δ+ charge.
2. ↑ δ+ H forms strong attraction with LP of e- on adjacent molecule, forming the H Bond.

Criteria:
1. H atom is bonded to F/ O /N atom.
2. LP of e- on F/O/N atom in a neighbouring molecule bearing δ- to attract δ+ of H atom.

H Bond can occur between the same, different types of molecules or within a molecule.

29
Q

H Bond

Effect on Physical Properties

A
  1. Extensiveness of H Bonding
  2. Strength of H Bond

H2 Chemistry (14 decks)

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