chemical bonding 4.3

Question 1

Coordinate covalent bond concept

Answer 1

One atom contributes both the bonding electrons to the bond.

Question 2

Examples of molecules with Coordinate covalent bond

Answer 2

1) Carbon monoxide
2) Hydronium ion (H3O+)
3) Ammonium ion
4) Al2Cl6 (Dimer formed between 2 molecules of AlCl3, the lone pair is shared by Cl atoms)

Question 3

Is there a difference between Coordinate covalent bond and covalent bond

Answer 3

Once its formed its identical to covalent bond

Question 4

VESPR theory

Answer 4

1) Used to predict geometry or shape of molecules
2) Electron pairs (lone or bonded) repel each other and spread as far apart as possible
3) Greatest repulsion between lone pair-lone pair

Question 5

Electron domain

Answer 5

Bonded or non-bonded pairs of electrons around an atom in a molecule.
1) Single, double, triple and lone pair of electrons are counted as 1 electron domain.

Question 6

4 Electron domains, 4 Bonding domains, 0 Lone pairs

Answer 6

1) Electron domain geometry= Tetrahedral
2) Molecular geometry= Tetrahedral
3) Bond angles =109.5 degrees
4) Example : CH4

Question 7

4 Electron domains, 3 Bonding, 1 lone pair

Answer 7

1) Electron domain geometry= Tetrahedral
2) Molecular geometry= Trigonal pyramidal
3) Bond angles = 107.8
4) Example : NH3

Question 8

4 Electron domains, 2 Bonding, 2 lone pairs

Answer 8

1) Electron domain geometry= Tetrahedral
2) Molecular geometry= Bent, V-shaped
3) Bond angles =104.5 degrees
4) Example : H2O

Question 9

3 Electron domains, 3 Bonding, 0 lone pairs

Answer 9

1) Electron domain geometry= Trigonal planar
2) Molecular geometry= Trigonal planar
3) Bond angles =120
4) Example : BF3

Question 10

3 Electron domains, 2 Bonding, 1 lone pairs

Answer 10

1) Electron domain geometry= Trigonal planar
2) Molecular geometry= Bent
3) Bond angles = <120
4) Example : SO2

Question 11

2 Electron domains, 2 Bonding, 0 lone pairs

Answer 11

1) Electron domain geometry= Linear
2) Molecular geometry= linear
3) Bond angles = 180
4) Example : CO2

Question 12

Types of Structure of covalent compounds

Answer 12

1) Molecular covalent

2) Giant covalent (network covalent)

Question 13

Molecular covalent

Answer 13

1) Exist as individual molecules
2) Fixed no of atoms
3) Lower MP and Bps.
4) Usually liquids and gases (exception : sulphur, iodine, phosphorus)
5) Low BP’s due to weak inter molecular forces
6) Solubility depends on the polarity of the molecule.
7) Dont conduct electricity due to the lack of charged particles

Question 14

Giant covalent (network covalent)

Answer 14

1) Dont exist as individual molecules
2) Dont Fixed no of atoms
3) High Mp’s BP’s due to strong covalent bonds between atoms
4) Examples: Diamond, Silicon, silicon dioxide.
5) Insoluble in both polar and non polar solvents
6) Dont conduct electricity due to the lack of charged particles

Question 15

Allotropes

Answer 15

Different forms of same element in same physical state

Question 16

Allotropes of Carbon

Answer 16

1) Graphite
2) Diamond
3) Fullerene (C60)
4) Graphene

Question 17

Graphite

Answer 17

1) Layered structure
2) Layers are held together by weak inter molecular forces. They can slide over each other therefore its soft.
3) Each carbon is bonded to 3 other Carbon atoms.
4) The bond angle is 120
5) Molecular geometry= Trigonal planar
6) Good conductor of electricity due to delocalized electrons

Question 18

Diamond

Answer 18

1) Giant molecular structure
2) High MP and BP
3) Very hard-due to strong covalent bonds between atoms
4) Each Carbon atom is bonded to 4 other carbon atoms.
5) Bond angle is 109.5
6) Doesn’t conduct electricity due to lack of delocalized electrons.

Question 19

Fullerene

Answer 19

1) 12 pentagons, 20 hexagons
2) Each Carbon atom is bonded to 3 other Carbon atoms
3) Bond angle=120
4) Molecular geometry= Trigonal planar
5) Shows some electrical conductivity

Question 20

Graphene

Answer 20

1) Very thin (1 layer thick)
2) But very strong
3) Each Carbon atom is bonded to 3 other Carbon atoms
4) Bond angle=120
5) Molecular geometry= Trigonal planar
6) Very good electrical and thermal conductivity

Question 21

Why do Reasonace structures occur ?

Answer 21

Resonance structures occur when there is more than one possible position for a multiple bond(single or double) in a molecule.
EXAMPLES: Nitrate ion (NO3-), Ozone O3
1) have delocalised electrons which are shared over more than 2 nuclei.

Question 22

What is resonance hybrid structure ?

Answer 22

Actual structure of the molecule or ion in which the bonds are of intermediate length and strength

Question 23

Types of Inter molecular forces

Answer 23

1) London dispersion
2) Dipole-dipole
3) Hydrogen bonding

Question 24

London dispersion forces

Answer 24

1) Weakest inter molecular forces
2) Exist between all molecules
3) As molar mass increases the strength of London dispersion forces increases too therefore it results in higher BP’s (Extra electrons with increased molar mass)
4) Trend can be easily seen in group 17 (Halogens)

Question 25

Dipole-dipole

Answer 25

1) Occur between polar molecules that have a net dipole movement
2) Second strongest type of inter molecular force

Question 26

Hydrogen bonding

Answer 26

Occurs when a hydrogen atom is bonded to either Nitrogen, Oxygen or Flourine atom.