Covalent bonding

Question 1

What is the difference between covalent bonds and ionic bonds?

Answer 1

In covalent bonds, the electrons are shared between atoms, while in ionic bonds, electrons are transferred from one atom to another.

Question 2

What is represented by a short straight line between two atoms?

Answer 2

A short straight line between two atoms represents a covalent bond.

Question 3

True or False?

Simple covalent molecules conduct electricity.

Answer 3

False.

Simple covalent molecules do not conduct electricity as they do not contain free electrons.

Question 3

What is a covalent bond?

Answer 3

A covalent bond is a type of chemical bond where atoms share pairs of electrons with each other.

Question 4

What are intermolecular forces?

Answer 4

Intermolecular forces are the weak forces of attraction that exist between individual molecules in a covalent substance.

Question 5

True or False?

Covalent bonds involve the transfer of electrons.

Answer 5

False.

Covalent bonds involve sharing electrons, not transferring them.

Question 6

What type of materials form a covalent bond?

Answer 6

The materials that form covalent bonds are non-metals.

Question 7

Where is the strong electrostatic attraction in a covalent bond?

Answer 7

The strong electrostatic attraction in covalent compounds is between the shared pair of electrons and the nuclei of the atoms involved.

Question 8

What makes each atom more stable in a covalent bond?

Answer 8

Sharing electrons in the covalent bond allows each atom to achieve an electron configuration similar to a noble gas.

Question 9

What is formed when a group of two or more atoms covalently bond together?

Answer 9

A compound / molecule is formed when a group of two or more atoms covalently bond together.

Question 10

True or False?

Dot and cross diagrams can represent giant covalent structures.

Answer 10

False.

Dot and cross diagrams are used to represent only small covalent molecules with a fixed number of atoms.

Question 10

What are simple molecules?

Answer 10

A simple molecule is a small covalent molecule with a fixed number of atoms, such as H2, Cl2, H2O, NH3, and CH4.

Question 11

What do dots and crosses represent in a dot and cross diagram?

Answer 11

In a dot and cross diagram, dots and crosses represents electrons.

Question 12

What are diatomic molecules?

Answer 12

Diatomic molecules are molecules composed of two atoms, such as H2, Cl2, O2, and N2.

Question 13

What are inorganic molecules?

Answer 13

Inorganic molecules are simple molecules that do not contain carbon atoms, such as H2O and NH2

Question 14

Name three inorganic molecules that you should be able to draw dot-and-cross diagrams for.

Answer 14

Three inorganic molecules that you should be able to draw dot-and-cross diagrams for are:

Water

Ammonia

Carbon dioxide

Question 14

What is the difference between simple covalent molecules and giant covalent structures?

Answer 14

Simple covalent molecules are small and can be separated into individual molecular units without breaking any chemical bonds.

Giant covalent structures are huge continuous networks of atoms that cannot be separated into individual units without breaking bonds.

Question 15

True or False?

You can be expected to draw dot-and-cross diagrams for the the diatomic molecules hydrogen, oxygen, nitrogen, halogens and hydrogen halides.

Answer 15

True.

You can be expected to draw dot-and-cross diagrams for the the diatomic molecules hydrogen, oxygen, nitrogen, halogens and hydrogen halides.

Question 16

What is an organic molecule?

Answer 16

An organic molecule is a simple molecule that contains carbon and hydrogen atoms, such as CH4, C2H6, and C2H4.

Question 17

How many carbon atoms (at this level) can be included in dot-and-cross diagrams?

Answer 17

Up to 2 carbon atoms can be included in dot-and-cross diagrams (at this level).

So, diagrams for methane, ethane, ethene and similar compounds with halogen atoms.

Question 17

True or False?

Simple molecular structures have high melting and boiling points.

Answer 17

False.

Simple molecular structures have low melting and boiling points.

Question 18

What is the difference between covalent bonds and intermolecular forces?

Answer 18

Covalent bonds are strong bonds that hold atoms together within a molecule, while intermolecular forces are weak attractive forces that exist between different molecules.

Question 19

True or False?

Covalent compounds are good conductors of electricity.

Answer 19

False.

Covalent compounds are poor conductors of electricity.

Question 20

What are simple molecular structures?

Answer 20

Simple molecular structures are small molecules with covalent bonds, which have weak forces between the molecules (intermolecular forces).

Question 21

What is the difference in melting / boiling point between simple molecular and giant covalent structures?

Answer 21

Simple molecular structures generally have low melting / boiling points, while giant covalent structures have high melting / boiling points.

Question 22

Why are covalent compounds generally poor conductors of electricity?

Answer 22

Covalent compounds are generally poor conductors of electricity because they do not contain free ions or electrons to carry the charge.

Question 23

True or False?

Covalent bonds break when a covalent substance melts or boils.

Answer 23

False.

Intermolecular forces break when a covalent substance melts or boils..

Question 24

What happens to melting and boiling points as the relative molecular mass of a substance increases?

Answer 24

As the relative molecular mass of a substance increases, the melting and boiling points also increase due to the increased number of electrons and stronger intermolecular forces.

Question 25

What are insulators?

Answer 25

Insulators are materials that do not allow the flow of electric charge or heat, and common insulators include plastics, rubber, and wood.

Question 26

Why do simple molecular structures have low melting and boiling points?

Answer 26

Simple molecular structures have low melting and boiling points due to weak intermolecular forces which require small amounts of energy to overcome.

Question 26

True or False?

Simple molecular structures are often gases or liquids at room temperature.

Answer 26

True.

Simple molecular structures are often gases or liquids at room temperature.

Question 27

What are giant covalent structures?

Answer 27

Giant covalent structures are macromolecules or giant lattices that consist of a huge number of non-metal atoms with strong covalent bonds in a fixed ratio.

Question 28

Define allotropes.

Answer 28

Allotropes are different structural forms of the same element, such as diamond and graphite for carbon.

Question 29

Why does diamond not conduct electricity?

Answer 29

Diamond does not conduct electricity because all of the outer shell electrons are held in the covalent bonds, and there are no freely moving charged particles to carry the current.

Question 30

True or False?

Graphite is used in pencils, as an industrial lubricant, in inert electrodes, and in cutting tools.

Answer 30

False.

Graphite is used in pencils, as an industrial lubricant, in inert electrodes, and in locks.

Diamond is used in cutting tools.

Question 31

What are fullerenes?

Answer 31

Fullerenes are a group of carbon allotropes that consist of molecules forming hollow tubes or spheres, such as C₆₀ (buckminsterfullerene or “buckyball”).

Question 32

Describe the structure of graphite

Answer 32

In graphite:

Each carbon atom is bonded to three others.

There are hexagonal layers.

There is one free / delocalised electron per carbon atom.

Question 33

True or False?

Graphite is harder than diamond.

Answer 33

False.

Diamond is harder than graphite.

Question 33

State the properties of diamond.

Answer 33

Diamond does not conduct electricity, has a high melting point, and is extremely hard.

Question 34

What are the properties of graphite?

Answer 34

Graphite conducts electricity and heat, has a high melting point, and is soft and slippery.

Question 35

True or False?

Fullerenes have a high surface area.

Answer 35

True.

Fullerenes have a high surface area.

Question 36

Describe Buckminsterfullerene.

Answer 36

Buckminsterfullerene is a carbon allotrope with 60 carbon atoms forming a hollow sphere, also known as a “buckyball”. Each carbon atom is bonded to three others and there is one free / delocalised electron per carbon atom.

Question 37

Why are C60 fullerene and graphite good electrical conductors?

Answer 37

C60 fullerene and graphite are good electrical conductors because they have delocalised electrons to carry the current.