Lesson 3: Covalent Bonding

Question 1

What is a molecule?

Answer 1

• A molecule is a collection of two or more atoms held by covalent bonds.

Question 2

What is a covalent bond?

Answer 2

• A covalent bond is a shared pair of electrons between 2 non- metals.

Question 3

What are the 3 ways covalent molecules can be represented?

Answer 3

• Ball and stick
• Dot and cross diagram
• stick model

Question 4

What is the P+ N of the ball and stick model?

Answer 4

P: shows 3D representation
N: doesn’t show where electrons are coming from.

Question 5

What is the P + N of the dot- cross diagram?

Answer 5

P: Shows where electrons come from.
N: Doesn’t give idea of shape of molecule.

Question 6

What is the P + N of stick diagram?

Answer 6

• P: Shows double bond/ single bond, shows atoms of different elements.
• N: Not clear where electrons came from, doesn’t show shape of molecule.

Question 7

How many bonds does Hydrogen form?

Answer 7

1 bond

Question 8

How do you know the number of covalent bonds an atom can form?

Answer 8

8- group number

Question 9

What makes covalent bonds very difficult to break?

Answer 9

• Both nuclei are attracted to pair of electrons.
• Takes a lot of energy to break .

Question 10

What are the properties of simple covalent molecules?

Answer 10

• Low melting + boiling points
• Don’t conduct electricity (molecules don’t have an overall charge.)

Question 11

What type of forces are between covalent molecules?

Answer 11

• Weak intermolecular forces.

Question 12

As you go down Group 7…. What happens to the melting/ boiling point?

Answer 12

• Gets higher
• Intermolecular forces are stronger because molecule is larger.

Question 13

What 3 types of covalent molecules are there?

Answer 13

• Small covalent molecules
• Large molecules (polymers)
• Giant covalent molecules

Question 14

What are simple molecules?

Answer 14

• A few atoms held together by covalent bonds.

Question 15

What does a line represent on displayed formula/ diagram?

Answer 15

• Represents 2 electrons
• 1 covalent bond

Question 16

What are the 3 types of structures that can be formed by covalent bonding?

Answer 16

• Simple molecules
• Giant covalent structures
• Polymers

Question 17

TRUE OR FALSE

The larger the molecules, the weaker the intermolecular forces.

Answer 17

• False!!
• The larger it is, the stronger the intermolcular forces are as it covers a larger area.

Question 18

Q.)

Explain why ethane has a lower boiling point than an alkane with 4 carbon atoms.

Answer 18

• Ethane is a smaller molecule than an alkane with 4 carbon atoms.
• So it will have weaker intermolecular forces.
• This will require little energy to break.

Question 19

Q.)

Describe, in terms of electron arrangement, the type of bonding in:

(i) a molecule of chlorine;

Answer 19

• Chlorine has 7 electrons on outer shell.
• Needs to gain 1 to be stable
• Shares a pair of electrons with another chlorine atom.
• This pair is a covalent bond.

Question 20

Explain, in terms of particles, why liquid iodine does not conduct electricity. (2)

Answer 20

• No delocalised electrons/ ions
• That can move and carry the charge.

Question 21

Would you expect hydrogen chloride to be a gas, a liquid or a solid, at room temperature and pressure? Explain your answer. (3)

Answer 21

• Gas
• Simple molecule
• With weak intermolecular forces
• Low boiling point

Question 22

Explain how covalent bonds are formed. (You may use a diagram).

Answer 22

1.) Pair of electrons shared
2.) This pair is a covalent bond.

Question 23

Describe the structure and bonding in diamond. (4).

Answer 23

• Giant covalent structure
• Each carbon bonds to 4 other carbon atoms by strong, covalent bonds.

Question 24

What state are most small covalent molecules at room temperature?

Answer 24

• Gas or liquid.