2.2.2 Bonding and structure

Question 1

State the three main types of chemical bonds?

Answer 1

ionic, covalent, metallic

Question 2

Define ionic bonding

Answer 2

Electrostatic attraction between oppositely charged ions

Question 3

Define covalent bonding

Answer 3

Electrostatic attraction between a shared pair of electrons and the nuclei of the bonded atoms

Question 4

Define metallic bonding

Answer 4

Electrostatic attraction between positive metal ions and delocalised electrons

Question 5

Explain how the conductivity of an ionic compound changes in solid and liquid state

Answer 5

solid - non-conductive as ions are fixed in position
liquid - conductive as ions are mobile and can carry charge

Question 6

Explain why ionic compounds have high melting and boiling points

Answer 6

Ionic compounds have a high melting and boiling point as the electrostatic attraction between oppositely charged ions is strong and requires a lot of energy to overcome.

Question 7

Explain the solubility of ionic compounds

Answer 7

Ionic compounds are soluble in polar solvents.
The oppositely charged ions are attracted to the slightly charged atoms of the solvent.

Question 8

What is a single covalent bond?

Answer 8

Atoms bonded by a single pair of shared electrons

Question 9

Define multiple covalent bonding

Answer 9

Atoms share more than one pair of electrons - double or triple bond.

Question 10

Define dative covalent bond

Answer 10

The electrons in the shared pair are supplied by one atom

Question 11

What is a lone pair?

Answer 11

Electrons in the outer shell that are not involved in bonding

Question 12

Define average bond enthalpy

Answer 12

A measurement of covalent bond strength
The average energy needed to break the bond

Question 13

Describe the bonding in simple molecular lattice structure

Answer 13

Atoms within a molecule are held by strong covalent bonds, each molecule is attracted to each other by weak intermolecular forces.

Question 14

Explain the low melting point of simple molecular structures

Answer 14

Weak intermolecular forces require little energy to overcome

Question 15

Explain the conductivity of simple molecule structures

Answer 15

Non-conductive
No free charged particles in the structure

Question 16

Explain the solubility of simple molecular structures

Answer 16

Soluble in non-polar solvents

Question 17

State and explain the properties of giant covalent structures e.g. graphite, silicon dioxide, diamond

Answer 17

High melting and boiling points - strong covalent bonds require a lot of energy to overcome

Non conductive - no free charged particles in structure (except graphite)

Insoluble - strong covalent bonds require a lot of energy to overcome

Question 18

Why is graphite conductive?

Answer 18

Each carbon atom in graphite form three covalent bonds with other carbon atoms
The delocalised electrons are free to move

Question 19

Describe linear shape and angle

Answer 19

2 bonding pairs, 0 lone pairs
180 degree angle

Question 20

Describe trigonal planar shape and angle

Answer 20

3 bonding pairs, 0 lone pairs
120 degree angle

Question 21

Describe tetrahedral structure and bond angle

Answer 21

4 bonding pairs, 0 lone pairs
109.5 degree angle

Question 22

Describe trigonal bi-pyramidal shape and bond angles

Answer 22

5 bonding pairs, 0 lone pairs
90 and 120 degree angles

Question 23

Describe octahedral shape and angle

Answer 23

6 bonding pairs, 0 lone pairs
90 degree angle

Question 24

describe pyramidal shape, bond angle and give an example

Answer 24

3 bonding angles, 1 lone pair
107 degree angle
NH3

Question 25

Describe non linear shape, bond angle and give example

Answer 25

2 bonding pairs, two lone pairs 104.5 degree angle H2O

Question 26

By how many degrees does a lone pair reduce a bond angle?

Answer 26

2.5 degrees

Question 27

Define electronegativity

Answer 27

The tendency for an atom to attract a shared pair of electrons in a covalent bond

Question 28

Define polar bond and permanent dipole

Answer 28

Polar bond - covalently bonded atoms with different electro-negativities Permanent dipole - slightly positive or negative charge of an atom in a polar bond

Question 29

Polar molecules must have...

Answer 29

Polar bonds with dipoles that do not cancel out due to their direction - this is determined by molecular shape

Question 30

Why is H2O polar but CO2 is not?

Answer 30

H2O has a non-linear molecular shape, and is asymmetrical, so there is an overall dipole. CO2 has a linear shape, and is a symmetrical molecule, so there is no overall dipole.

Question 31

Describe Van der Waals' forces

Answer 31

An intermolecular force caused by attraction between dipoles Broad term for dipole interactions and London forces.

Question 32

Describe permanent dipole-dipole interactions

Answer 32

Intermolecular attraction between two polar molecules

Question 33

Describe induced dipole-dipole interactions

Answer 33

Intermolecular attraction between a polar molecule and a non polar molecule with an induced dipole.

Question 34

Describe London forces and how do they become greater?

Answer 34

Intermolecular attraction between instantaneous dipoles caused by random movements of electrons in a molecule. London forces are greater in molecules with more electrons.

Question 35

Describe hydrogen bonding

Answer 35

Strong intermolecular bond between H atom and a lone pair of electrons on O, N or F. Forms an O-H, N-H or F-H bond.

Question 36

Explain why ice is less dense than water?

Answer 36

Water molecules with hydrogen bonding arrange in an open lattice structure. Molecules in ice are further apart than in liquid water.

Question 37

Explain why water has a higher melting and boiling point than expected d

Answer 37

Hydrogen bonding is a relatively strong intermolecular force, so more energy is required to overcome this.

Question 38

What must be always stated about electron bond pair in molecular shape questions?

Answer 38

- Electron pairs repel as much as possible - Lone pairs repel more than electron bonding pairs