Covalent Bonds

Question 1

Covalent bonds…

Answer 1

-are strong
-form between non-metal atoms
-often produce molecules
(elements or compounds)

-all atoms want to be stable

Question 2

When is a covalent bond formed?

Answer 2

when a pair of electrons is shared between 2 atoms

Question 3

How many bonds can a hydrogen atoms form?

Answer 3

one

Question 4

How do you work out how many bonds a non-metal atoms can form?

Answer 4

number of bonds = 8 - group number

Question 5

How can you represent covalent bonds?

Answer 5

dot-and-cross (with shells)

dot-and-cross (without shells)

structural formula/stick diagram
(e.g. H-H)

Question 6

How do you draw dot and cross diagrams?

Answer 6

• draw overlapping circles to represent the outer shells
• draw a dot to represent an electron from one atom, and a cross to represent an electron from the other atom
• make sure each bonding pair of electrons is between the two atoms
• make sure that each atoms (other than hydrogen) has eight electrons in its outer shell
• if there is more than one bond, place it with the others in the overlapping part of the circles

Question 7

How do you draw stick diagrams?

Answer 7

• write the symbols for the atoms

- use a single line to represent one pair of shared electrons, two for two pairs etc.

Question 8

Describe covalent bonding

Answer 8

(strong) bond formed when a pair of electrons is shared between two atoms

Question 9

Methane, CH₄, can be represented by this structure:

......H
......|
H − C − H
......|
.....H

Draw a dot and cross diagram to represent methane.

Answer 9

• 4 hydrogen atoms overlapping 1 carbon in the middle

- 4 total pairs between the carbon and hydrogen atoms

Question 10

Draw a dot and cross diagram to represent a molecule of oxygen, O₂

Answer 10

• two overlapping circles with two dots and two crosses in the overlap
• two pairs of non-bonding electrons in each oxygen atom