Ionic Bonding
5 marks · EasyThis question is about common ions and how they are formed, using magnesium oxide and calcium fluoride as examples.
Write the formula and charge of the ion formed by a magnesium atom.
Explain why oxygen forms an ion with a negative charge.
Calcium fluoride has the formula . What is the charge on a fluoride ion?
Describe how calcium forms its ion. Mention what happens to its electrons.
Sodium and sulphur can also form ions. Give the formula and charge of the ion formed by sulphur.
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(a) Mg2+
(b) Oxygen gains 2 electrons to achieve a full outer shell, resulting in a 2- charge.
(c) 1-
(d) Calcium loses 2 electrons from its outer shell to form a Ca2+ ion.
(e) S2-
Show mark scheme and worked solution
Marking points
A1 (a) · 1 mark · Correct formula and charge for magnesium ion (Mg2+).
B1 (b) · 1 mark · Explanation of oxygen gaining electrons to form a 2- ion.
A2 (c) · 1 mark · Correct charge for fluoride ion (1-).
B2 (d) · 1 mark · States calcium loses 2 electrons (to form Ca2+).
A3 (e) · 1 mark · Correct formula and charge for sulphur ion (S2-).
Worked solution
a) Mg2+
b) Oxygen needs to gain two electrons to fill its outer shell, becoming O2-.
c) The fluoride ion has a 1- charge.
d) Calcium loses two electrons from its outer shell, forming Ca2+.
e) Sulphur forms the S2- ion.