Chemical Changes & Structure: Bonding

Question 1

State why elements form bonds.

Answer 1

Elements form bonds in order to have a full outer electron arrangement.

This is because having a full outer electron arrangement makes an element stable like a noble gas.

Question 2

What types of elements are usually found in covalent substances?

Answer 2

Covalent substances usually contain two non-metals.

Question 3

Define the term ‘Covalent Bond’.

Answer 3

A covalent bond is a shared pair of electrons between two positively charged nuclei.

Question 4

What are the two types of covalent substances?

Answer 4

The two types of covalent substances are covalent networks & covalent molecules (sometimes called discrete molecules).

Question 5

What is a molecule?

Answer 5

A molecule is a group of atoms held together by covalent bonds. It is often referred to as a covalent molecule.

Question 6

Define the term ‘Diatomic Molecule’.

Answer 6

A diatomic molecule is one that contains only 2 atoms.

Question 7

What are the 7 diatomic elements?

Answer 7

Hydrogen, Fluorine, Chlorine, Bromine, Iodine, Oxygen, Nitrogen.

Hint: ‘Have No Fear Of Ice Cold Beer’

Question 8

When a molecule has 4 bonds (Formula XY₄), what type of shape does it have?

Answer 8

A molecule that has 4 bonds will have a tetrahedral shape.

Question 9

When a molecule has 3 bonds (Formula XY₃), what type of shape does it have?

Answer 9

A molecule that has 3 bonds will have a trigonal pyramidal shape.

Question 10

When a molecule has 2 bonds (Formula X₂Y), what type of shape does it have?

Answer 10

A molecule which has 2 bonds will have an angular shape.

Question 11

When a molecule has a single bond (Formula XY), what type of shape does it have?

Answer 11

A molecule which has a single bond will have a linear shape.

H - Cl

Question 12

What are “double covalent bonds” and “triple covalent bonds”?

Answer 12

Double covalent bonds are when there are two pairs of electrons within the sharing zone.

Triple covalent bonds are when there are three pairs of electrons within the sharing zone.

Bonus: At national 5 we only encounter one molecule which contains a triple covalent bond, which is nitrogen.

Question 13

Describe the structure of a covalent molecule in terms of the strength of the bonds within the molecule and between the molecule.

Answer 13

Within a covalent molecule, there are strong covalent bonds.

Between covalent molecules, there are weak intermolecular bonds.

Question 14

Describe the structure of covalent networks in terms of the strength of bonds and size of the structure.

Answer 14

All of the covalent networks substances in existence contain non-metal and have a giant lattice of millions of atoms joined together with strong covalent bonds.

Question 15

Why do covalent molecules have low melting/boiling points?

Bonus: What state are they at room temperature?

Answer 15

Covalent molecules have strong covalent bonds within their molecules.

The forces of attraction between molecules are weak, and hence do not require much energy to break.

Bonus: At room temperature, they are liquid or gas.

It is only these weak forces that must break in order to change the state.

Question 16

Why do covalent networks have high melting/boiling points?

Bonus: What state are they at room temperature?

Answer 16

Covalent Networks have very high melting and boiling points because, in order to change state, the strong covalent bonds within the network must be broken.

This process requires a lot of energy.

Bonus: They are solid.

Question 17

Describe the solubility of covalent substances.

Answer 17

Covalent substances are insoluble in water, but may be soluble in different solvents.

Question 18

Explain the conductivity of covalent substances.

Bonus: What is the one exception to this?

Answer 18

They do not conduct, because they have no charged particles which are free to move.

Bonus: Graphite is the only exception, meaning carbon is the only non-metal that conducts.

Question 19

What are the types of elements usually found in ionic substances?

Answer 19

In Ionic substances, there is usually a metal and non-metal.

Question 20

State how ions are formed, and why atoms form ions.

Answer 20

Ions are formed by the loss or gain of electrons.

Atoms form ions because they would like to have a full outer electron arrangement in order to be stable like a noble gas.

Question 21

State what charge a metal ion and a non-metal ion would have, and how they achieve this.

Answer 21

A metal ion would have a positive charge, and a non-metal ion would have a negative charge.

This is because the metal would lose electrons, and the non-metal would gain electrons

Question 22

Define the term ionic bond.

Answer 22

The electrostatic force of attraction between two oppositely charged ions.

Question 23

Describe the structure of an ionic compound.

Answer 23

An Ionic compound is structured in a crystal (lattice) of oppositely charged ions.

Question 24

How would you construct ionic formulae for ionic compounds?

Answer 24

To construct ionic formulae for ionic compounds, first, you must go through the valency rule.

After going through the valency rule, put brackets around any element that has more than one atom.

Finally, put your charges in, outside of the brackets where applicable.

Question 25

Explain why an ionic compound has high melting and boiling points.

Bonus: what state are ionic compounds at room temperature?

Answer 25

Ionic compounds have high melting and boiling points because the strong ionic bonds within the ionic compound must be broken in order to change state.

Bonus: They are solids.

Question 26

Explain the conductivity of ionic compounds.

Answer 26

Ionic substances do not conduct while solid because the ions are held in a lattice and are not free to move.

However, they do conduct when liquid (molten) or in solution, because the lattice is broken up and the ions are free to move.

Question 27

What are the 6 covalent networks?

Answer 27

Graphite, Silicon, Silicon Carbide, diamond, boron, or silicon dioxide.

Question 28

How are the chemical formulae for covalent networks structured?

Answer 28

The formulae of covalent networks give the simplest ratio of each type of atom.