3: Bonding and Intermolecular Forces

Question 1

What is electron pair repulsion theory?

Answer 1

Electrons are all negatively charged so they repel each other and try to be as far apart as possible.

Question 2

Name the shape of a molecule with 2 bonding pairs.
Give the bond angle.

Answer 2

Linear
180

Question 3

Name the shape of a molecule with 3 bonding pairs.
Give the bond angle.

Answer 3

Trigonal planar.
120

Question 4

Name the shape of a molecule with 4 bonding pairs.
Give the bond angle.

Answer 4

Tetrahedral
109.5

Question 5

Name the shape of a molecule with 3 bonding pairs and 1 lone pair.
Give the bond angle.

Answer 5

Trigonal pyramidal
107

Question 6

Name the shape of a molecule with 2 bonding pairs and 2 lone pairs.
Give the bond angle.

Answer 6

Bent
104.5

Question 7

Name the shape of a molecule with 5 bonding pairs.
Give the bond angles.

Answer 7

Trigonal bipyramidal.
90 and 120

Question 8

Name the shape of a molecule with 4 bonding pairs and 1 lone pair.
Give the bond angles.

Answer 8

See saw
86.5
102

Question 9

Name the shape of a molecule with 3 bonding pairs and 2 lone pairs.
Give the bond angle.

Answer 9

T shape.
87.5

Question 10

Name the shape of a molecule with 6 bonding pairs.
Give the bond angle.

Answer 10

Octahedral
90

Question 11

Name the shape of a molecule with 5 bonding pairs and 1 lone pair.
Give the bond angle.

Answer 11

Square pyramidal
90

Question 12

Name the shape of a molecule with 4 bonding pairs and 2 lone pairs.
Give the bond angle.

Answer 12

Square planar.
90

Question 13

Give the shape of CO2.

Answer 13

Linear
180

Question 14

Give the shape of SO2.

Answer 14

Bent
120

Question 15

What is a dipole?

Answer 15

An uneven distribution of charge caused by a shift in electron density in a bond.

Question 16

Define electronegativity.

Answer 16

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

Question 17

Describe how van der waals forces form.

Answer 17

At any moment, electrons can be distributed on either side of a molecule. This means one side is more positive or more negative (temporary dipole). This induces a temporary dipole in another neighbouring atom. This continues throughout a set of molecules because they are always moving, meaning that dipoles are constantly being created and destroyed. This means there is constant attraction throughout.

Question 18

Describe molecules that form stronger van der waals forces.

Answer 18

Larger molecules, because they have larger electron clouds.

Question 19

Describe the shape of molecules that allow for stronger van der waals forces.

Answer 19

Straight, unbranched, linear molecules because they can pack closer together and form stronger forces.

Question 20

Why do molecules with stronger van der waals forces have higher boiling points?

Answer 20

More energy is required to overcome the boiling point.

Question 21

What are permanent dipole-dipole forces?

Answer 21

IMFs that occur between molecules with a permanent dipole. The slightly negative side of a molecule with a dipole attracts to the slightly positive side of a neighbouring molecule.

Question 22

Hydrogen bonds can only be formed between hydrogen and what 3 other atoms?
Why?

Answer 22

N, O, F
These atoms are very electronegative so draw the electrons away from the hydrogen atoms.

Question 23

Describe how hydrogen bonds are formed.

Answer 23

A dipole is formed between hydrogen and N, O, F. This means the hydrogen is slightly positive and slightly negative. In neighbouring molecules, the slightly positive hydrogen attracts to the lone pairs on the electronegative atom.

Question 24

What happens when liquids with hydrogen bonds cool and become solid?

Answer 24

They arrange themselves into a regular lattice structure.

Question 25

Why are substances with hydrogen bonds less dense as solids?

Answer 25

The length of hydrogen bonds is longer so molecules are further apart.

Question 26

List the types of IMF in order from weakest to strongest.

Answer 26

Van der waal
Permanent dipole-dipole
Hydrogen bond

Question 27

Why dont simple covalent molecules conduct?

Answer 27

There are no free ions to carry charge.

Question 28

Why do simple covalent molecules have low melting point?

Answer 28

IMFs require little energy to be overcome.

Question 29

Describe the solubility of simple covalent molecules.

Answer 29

Dissolve in water depending on how polarised the molecule is.

Question 30

Why does boiling point increase from HCl to HI?

Answer 30

Polarity decreases
Number of electrons in molecules increases so the strength of the induced dipole-dipole interactions increases.

Question 31

Describe metallic bonding?

Answer 31

Positive metal ions surrounded by a sea of delocalised electrons.

Question 32

Compare the strength of Na and Mg.

Answer 32

Mg stronger than Na. This because the charge on Mg is 2+ but the charge on Na is 1+. This means that in Mg there is a stronger ion charge and more delocalised electrons, so the metal is stronger.

Question 33

Why can metals be shaped easily?

Answer 33

There are no bonds holding specific ions together so metal ions can slide over each other and be shaped.

Question 34

Why do metals conduct?

Answer 34

The metal ions have positive charge so charge can pass through.