Bonding

Question 1

What is covalent bonding?

Answer 1

A pair of electrons of opposed spins shared between two nuclei.

Question 2

What is ionic bonding?

Answer 2

Formed by attractions between positive and negative ions.

Question 3

What is a co-ordinate bond?

Answer 3

A covalent bond where both electrons come from one atom in the bond, such a bond will be polar to some extent.

Question 4

What is electronegativity?

Answer 4

The ability of an atom to draw electrons towards itself in a covalent bond.

Question 5

Describe the attractions and repulsions of electrons in covalent bonding

Answer 5

The electrons in the pair between the atoms repel one another but this is overcome by their attractions to both nuclei. The nuclei will also have nucleus-nucleus repulsion.

Question 6

Describe the attractions and repulsions of ions in ionic bonding

Answer 6

Cations and anions are arranged so that each cation is surrounded by several anions and vice versa to maximise attraction and minimise repulsion.

Question 7

What is a dipole?

Answer 7

Separation of charge within a molecule. Electrical charges are not balanced so that one part has a partial negative charge and another an equal positive charge.

Question 8

What is intermolecular bonding?

Answer 8

Bonding between molecules, weak and governs physical properties.

Question 9

What is intramolecular bonding?

Answer 9

Bonding within molecules, strong and governs chemical reactivity.

Question 10

What is hydrogen bonding?

Answer 10

Highest bonding between hydrogen and an electronegative element such as fluorine, oxygen or nitrogen which bonds to a similar element in another molecule.

Question 11

Why is hydrogen bonding the strongest intermolecular force?

Answer 11

As the hydrogen atom is sandwiched and allows close approach.

Question 12

What are Van der Waals forces?

Answer 12

Weak intermolecular forces that exist between all atoms and molecules. They are electrical in nature and originate through the attraction between opposite charges.

Question 13

What molecules have permanent dipole-dipole attraction?

Answer 13

Molecules with polar bonds.

Question 14

What is a bond pair?

Answer 14

Two electrons with opposed spins that bond two atoms in a molecule by a covalent or co-ordinate bond.

Question 15

What is the repulsion sequence?

Answer 15

lone pair- lone pair > lone pair- bond pair > bond pair- bond pair

Question 16

Features of a linear structure?

Answer 16

Two bond pairs at 180 degrees.

Question 17

Features of a trigonal planar structure?

Answer 17

Three bond pairs at 120 degrees.

Question 18

Features of a tetrahedral structure?

Answer 18

Four bond pairs at 109.5 degrees.

Question 19

Features of a trigonal bipyramidal structure?

Answer 19

Five bond pairs at 120 and 90 degrees.

Question 20

Features of an octahedral structure?

Answer 20

Six bond pairs at 90 degrees.

Question 21

What is a solute?

Answer 21

The substance that dissolves in the solvent.

Question 22

What is a solvent?

Answer 22

The liquid medium in which the solute dissolves, commonly water.

Question 23

What does saturated mean?

Answer 23

A solution that cannot dissolve any more solute under the existing conditions.

Question 24

What does polar mean?

Answer 24

A molecule with some separation of positive and negative charge.

Question 25

Why are some covalent bonds polar?

Answer 25

Bonds which make up the bond have differences in electronegativity.

Question 26

Why do molecules take up different shapes?

Answer 26

To minimise repulsion between electron pairs.

Question 27

Give an example of a co-ordinate bond

Answer 27

NH4+.

Question 28

Why are electronegativity values useful when considering bond polarity?

Answer 28

As the difference between the two values for the atoms in the bond is proportional to bond polarity.

Question 29

What effect do Van der Waals forces have on physical properties?

Answer 29

The boiling temperature of a liquid is governed by the strength of the Van der Waals forces between the molecules.

Question 30

What are the two types of Van der Waals forces?

Answer 30

In one, the molecules are polar and have permanent charge separation. In the other, fluctuating dipoles induced by electron movements come into phase to give an attractive force between the molecules.

Question 31

Give examples of the two types of Van der Waals forces

Answer 31

Dipole- dipole: Hydrogen iodide
Induced dipole- Induced dipole: Helium

Question 32

Explain the boiling temperatures of liquids containing hydrogen bonds

Answer 32

The boiling temperatures of liquids containing hydrogen bonds are higher than expected because the molecules in the liquid are held together more strongly so that more energy is needed to separate them.

Question 33

Explain the effect of solubility of compounds in water

Answer 33

Compounds such as lower alcohols having O-H bonds will be soluble in water through hydrogen bonding with the water. Many ionic solids are also soluble in water because of the interaction of the cation with the polar oxygen and the anion with the hydrogen atoms in the water.

Question 34

Why do lone pairs repel more than bond pairs?

Answer 34

As they are more localised around the central atom while bond pairs are stretched out between the bonded atoms.