Covalent bonding

Question 1

What is covalent bonding?

Answer 1

A covalent bond is an electrostatic attraction between the shared pair of electrons and the positively charged nuclei of two atoms

Question 2

Why do simple covalent structures have low boiling points?

Answer 2

They have very low boiling point because the intermolecular forces between the molecules are weak and only need a small amount of energy to overcome.

Question 3

What are the different types of covalent bonds?

Answer 3

Simple covalent
Giant covalent

Question 4

How are covalent bonds represented?

Answer 4

A line between the atoms e.g. h-h

Question 5

Why are covalent bonds formed?

Answer 5

To complete an outer shell

Question 6

Why when Hydrogen bonds is Hydrogen not helium?

Answer 6

Because the identity of an element is based on the number of protons.

Question 7

Why do bonds make the ions more stable?

Answer 7

When a chemical reaction takes place, energy is released leaving the product with less energy making it more stable.

Question 8

What is the relation of a paired share of electrons to another (in terms of positioning)

Answer 8

The shared electrons move as far away as possible, because electrons repel each other

Question 9

Can water be bent?

Answer 9

Water can be bent
Slightly polar ends
electrical charged object to water -> bend

Question 10

how are double covalent bonds represented?

Answer 10

two lines

Question 11

draw dot and cross diagrams

Question 12

How are covalent structures held together between molecules?

Answer 12

Weak intermolecular forces

Question 13

Trend between melting and boiling point of halogens

Answer 13

up the group
higher melting and boiling points

Question 14

Do covalent ions conduct electricity

Answer 14

no except graphene or graphite

Question 15

Do covalent structures dissolve in water?

Answer 15

Covalent structures usually do not dissolve in water.

Question 16

arrangement in diamond

Answer 16

tetrahedral arrangement, giant covalent

Question 17

Graphite structure

Answer 17

Graphite’s structure is a bit like a layer structure, but still giant covalent structure with layers in between.

Question 18

structure of C60 fullerene

Answer 18

C60 fullerene is a simple covalent structure with a delocalised electron per carbon atom, but they cannot move between molecules.

Question 19

Trend between M(small r) and intermolecular forces

Answer 19

Usually intermolecular forces are stronger when there is a higher relative molecular mass but not always.

Question 20

Graphite’s structure

Answer 20

Layers with 3 shared electrons and delocalised electrons which means graphite can conduct electricity. There are weak intermolecular forces between the layers making graphite soft.

Question 21

Why is melting point of diamond high(around 4000 degrees celcius)?

Answer 21

Diamond has a very high melting point. This is because diamond is in a giant covalent structure (or macro molecular covalent). This means that there are millions of strong covalent bonds between the carbon atoms. This is a strong structure and is hard to break. This means that a lot of energy is needed to break all the bonds.

Question 22

Why does Fullerene have a low melting and boiling point?

Answer 22

Fullerene has a low melting point. This is because fullerene is in a simple molecular structure and there are weak intermolecular bonds between the atoms. This means that little energy is needed to overcome these bonds.

Question 23

Explain why simple covalent molecules have:

1) Low melting points
2) Cannot conduct electricity

Answer 23

Simple covalent molecules cannot conduct electricity as there are no delocalised electrons or oppositely charged ions. Simple covalent molecules have a low melting point because they have weak intermolecular forces. These forces are weak and easy to overcome.

Question 24

Explain why:

Giant covalent structures have high melting/boiling points?

Answer 24

1. Giant covalent structures have a high boiling point
2. This is because giant covalent have a giant covalent structure
3. This means that there are many covalent bonds
4. These bonds are strong and hard to break requiring a lot of thermal energy to break them

Question 25

List the:

Halogens

(including their colour and state of matter at room temperature)

Answer 25

• Fluorine, yellow, gas
• Chlorine, green, gas
• Bromine, orange, liquid (amber gas)
• Iodine, grey, solid, purple gas

Question 26

what is the bonding and structure of a metal?

Answer 26

metallic bond, strong electrostatic forces of attraction between the positive nuclei of the metal and the delocalised electron in the giant metallic lattice

Question 27

Explain why metals have a high boiling point, can conduct electricity, and are ductile/malleable

Answer 27

1. Metals have a high melting point due to the strong electrostatic forces between the positive metal nucleus and the delocalised electron in the giant metallic lattice which is strong. This bond is hard to overcome.
2. Metals are ductile and malleable. This is because the metal can slide over each other without breaking.
3. Metals can conduct electricity. This is because of the free delocalised electrons that are free to move and can flow.

Question 28

Define the key term covalent bonding, give examples of simple covalent molecules

Answer 28

A covalent bond is electrostatic forces of attraction between the shared pair of electrons and the positively charged nuclei of two atoms

Question 29

Explain why halogens have a similar chemical reactivity

Answer 29

They have similar chemical reactivity because they have the same number of electrons on their outer shell. This means that the halogens will all react to gain 1 electron

Question 30

explain why Group 7 elements decrease in reactivity

Answer 30

Because the outer electron is further away from the positive nucleus so the force of electrostatic attraction of the nucleus is not as strong decreasing the reactivity.

Question 31

What is displacing? give examples

Answer 31

When a more reactive halogen displaces a less reactive halogen to bond with a metal.
2KI + Cl2 -> 2KCl + I2
2Br + Cl2 -> 2KCl + Br2