6.1 Chemical bonds

Question 1

define molecule

Answer 1

a group of 2 or more atoms joined together

Question 2

define covalent bond

Answer 2

a bond made when a pair of electrons is shared by 2 atoms

Question 3

define dot-and-cross diagram

Answer 3

a diagram used to show a covalent bond between atoms in a molecule. Electrons are represented by dots or crosses

Question 4

define ion

Answer 4

an atom which has gained at least one electron to be negatively charged or lost at least one electron to be positively charged

Question 5

define ionic bond

Answer 5

an attraction between a positively charged ion and a negatively charges ion

Question 6

explain why oxygen had the formula O2 and water has the formula H2O

Answer 6

Oxygen is represented as O2 because oxygen molecules typically exist in pairs. Water is defined as H2O because a water molecule has two hydrogen atoms covalently bonded to a single oxygen atom.

Question 7

“Only compounds are made up of molecules.”
Explain why this statement is wrong

Answer 7

Because molecules can be made with 2 atoms of the same element. (e.g. oxygen, hydrogen)

Question 8

why is oxygen known as a ‘diatomic molecule’

Answer 8

because it exists as 2 atoms

Question 9

why do sodium atoms have no overall charge?

Answer 9

because it has the same number of protons and electrons.

Question 10

when sodium reacts with chlorine, ions are formed. Why?

Answer 10

Sodium and chloride form an ionic bond. An electron is transferred from the sodium atom to the chloride atom and so both atoms become ionic and have a full outer shell.

Question 11

Draw a diagram to show what happens when a magnesium atom reacts with an oxygen atom to form magnesium oxide (MgO). What are the charges on each ion?

Answer 11

Question 12

What is a cation?

Answer 12

positively charged ion (e.g Na +)

Question 13

What is an anion?

Answer 13

negatively charged ion (e.g Cl - )