Properties of Compounds of Non-metals and Covalent Bonding

Question 1

Covalent substances are generally not able to conduct electricity because:
(a) their electrons are localised.
(b) their electrons are delocalised.
(c) their electrons are transferred.
(d) their electrons are shared.

Answer 1

A

Question 2

Which of the following formulas represents a substance that contains twice as much hydrogen as oxygen, and half as much carbon as oxygen?
(a) C4H8O6
(b) C2H6O3
(c) C3H12O6
(d) C5H10O3

Answer 2

c

Question 3

Which of the following are covalent compounds?

(i) Hydrogen peroxide
(ii) Carbon monoxide
(iii) Potassium hydroxide
(iv) Copper(II) phosphate
(v) Sulfurous acid

(a) (i), (ii) and (v) only
(b) (ii) and (v) only
(c) (i) and (ii) only
(d) (ii), (iii) and (v) only

Answer 3

A

Question 4

What are some examples of non-metal compounds?

Answer 4

Water, carbon dioxide, caffeine, sugar and cooking oil are just a few examples of common compounds formed from non-metals.

Question 5

What are the properties of non-metal compounds?

Answer 5

• Low boiling points and do not conduct electricity.
• Low melting points.

Question 6

Why do non-metallic elements and compound not conduct electricity?

Answer 6

In general, non-metallic elements and compounds do not conduct electricity because they do not contain free-moving charged particles (neither delocalised electrons nor ions).

Question 7

Why do non-metallic elements and compounds have low melting and boiling points?

Answer 7

The melting and boiling points of non-metallic elements and compounds depend on the intermolecular forces between molecules. Generally, these molecular substances have low melting and boiling points and, when solid, the solids tend to be soft. This indicates they have weak forces of attraction between molecules.

Question 8

What are many non-metal compounds composed of?

Answer 8

Molecules

Question 9

What are molecules?

Answer 9

Molecules are discrete groups of atoms of known formula, bonded together.

Question 10

What are the two types of forces of attraction in molecular compounds?

Answer 10

• Intramolecular bonds
• Intermolecular forces

Question 11

What are intramolecular bonds?

Answer 11

The bonds within a molecule.

Question 12

What are intramolecular forces?

Answer 12

The attraction between molecules.

Question 13

What happens to electrons in covalent bonds?

Answer 13

Electrons are shared between atoms.

Question 14

What atoms do covalent bonds occur between?

Answer 14

Non-metals.

Question 15

What are the three different types of covalent bonds?

Answer 15

• Single
• Double
• Triple

Question 16

What is a single covalent bond?

Answer 16

The covalent bond when atoms share two electrons, one from each atom.

Question 17

What is an example of a single covalent bond?

Answer 17

H2

Question 18

What is a double covalent bond?

Answer 18

In a double covalent bond, two pairs of electrons (four electrons in total) are shared between the atoms, rather than just one pair.

Question 19

What is an example of a double covalent bond?

Answer 19

O2

Question 20

What is a triple covalent bond?

Answer 20

A triple covalent bond occurs when three electron pairs are shared between two atoms.

Question 21

What is an example of a triple covalent bond?

Answer 21

N2

Question 22

What are molecules called that contain 2 atoms of one type?

Answer 22

Diatomic molecules

Question 23

What are polyatomic molecules?

Answer 23

Molecules mad up of more than two atoms.

Question 24

What are two examples of polyatomic molecules?

Answer 24

• Water
• Methane

Question 25

What are two types of covalent bonds?

Answer 25

• Polar
• Non-polar

Question 26

Describe non-polar covalent bonds.

Answer 26

• There are equal sharing of electrons between the two atoms to form a bond.
• Equal charge in the bond.

Question 27

Describe polar covalent bonds.

Answer 27

• Unequal sharing of electrons between the two atoms to form a bond.
• Charge separation in the bond.
• One atom attracts the electrons more than the other.

Question 28

How does electronegativity affect the electron cloud?

Answer 28

The electron cloud is more towards the higher electronegative atom.

Question 29

How does electronegativity affect the polarity of the bond?

Answer 29

The polarity +/- depends on the difference between the electronegativity valves of the atoms framing the bond.

Question 30

What is dipole movement?

Answer 30

Property of a molecule whose charge distribution can be represented by a centre of positive charge and a centre of negative charge.

Question 31

What is a Lewis Structure?

Answer 31

A model representing the distribution of valence electrons in molecules.

Question 32

What are lone pairs?

Answer 32

The non-bonding pairs of electrons.

Question 33

What are the steps to draw a Lewis Structure?

Answer 33

1. Find the total number of valence electrons in the molecule.
2. Place the atom with the lowest electronegativity value as the central atom.
3. Place the valence electrons within the molecule. Single bond between each pair of bonded atoms.
4. Use any remaining pairs as lone pairs around each terminal atom.
5. Move lone pairs to satisfy octet rule.

Question 34

Can Lewis Structures be used to show the shapes of molecules?

Answer 34

No Lewis Structures are used to determine the number and type of bonds present.

Question 35

What diagrams show the shape of molecules?

Answer 35

Ball-and-stick model

Question 36

What diagrams show the position of atoms?

Answer 36

Space-filing models.

Question 37

Describe a ball-and-stick model.

Answer 37

Sphere = atoms
Rods = bonds

Question 38

Describe a space-filing model.

Answer 38

Sphere = whole atoms
Other colour spheres = different elements