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1.1.4Relative charges of subatomic particles

AQA GCSE Chemistry (8462), Higher tier · Atomic structure and the periodic table › Atoms, isotopes and electronic structure

Practise Relative charges of subatomic particles. 11 exam-style questions plus unlimited generated ones on this subtopic, at up to four difficulty levels, with full mark schemes and a progress tracker. Free, no account needed.

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An atom of fluorine has 9 protons.
How many electrons does it have?
9
An aluminium ion has 13 protons and 10 electrons.
Give the relative charge on the ion.
3+
A molecule contains 5 atoms and a total of 10 electrons. The molecule contains hydrogen and one other element.
Deduce the formula of the molecule.
CH4

Sample questions

Written for this site in the style of AQA exam questions. They are not taken from real past papers.

Question 1Easy6 marks
Atoms contain protons, neutrons and electrons. A proton has a relative charge of +1.
(a) What is the relative charge of a neutron?
Tick (✓) one box.[1]
  • −1
  • 0
  • +1
  • +2
(b) What is the relative charge of an electron?
Tick (✓) one box.[1]
  • −1
  • 0
  • +1
  • +2
(c) Explain why an atom has no overall electrical charge.[2]
(d) An atom of fluorine has 9 protons.
How many electrons does it have?[1]
(e) What name is given to the number of protons in an atom?[1]
Show the answer and mark scheme
(a) Answer: 0
(b) Answer: −1
(c) Answer: The number of electrons equals the number of protons, so the positive and negative charges cancel.
  • number of electrons = number of protons
  • so the (positive and negative) charges cancel (out)
(d) Answer: 9
  • 9
(e) Answer: atomic number
  • atomic number
Question 2Medium5 marks
A magnesium atom has 12 protons. It can lose two electrons to form a magnesium ion.
(a) How many electrons does a magnesium atom have?[1]
(b) Use the relative charges of protons and electrons to calculate the charge on a magnesium ion.
Show your working.[2]
(c) An oxide ion has 8 protons and a charge of 2−.
How many electrons does an oxide ion have?[1]
(d) Explain why a magnesium ion has almost the same mass as a magnesium atom.[1]
Show the answer and mark scheme
(a) Answer: 12
  • 12
(b) Answer: 2+
  • (12 × +1) + (10 × −1) / 12 protons and 10 electrons
  • = +2 / 2+
(c) Answer: 10
  • 10
(d) Answer: Electrons have a very small mass, so losing two electrons makes almost no difference to the mass.
  • electrons have a very small (relative) mass, so losing 2 electrons hardly changes the mass
Question 3Hard6 marks
Ions can contain one atom or several atoms bonded together.
Atomic numbers: H = 1, O = 8, Al = 13, S = 16, Fe = 26
(a) An aluminium ion has 13 protons and 10 electrons.
Give the relative charge on the ion.[1]
(b) A hydroxide ion, OH−, contains one oxygen atom and one hydrogen atom.
Calculate the total number of electrons in a hydroxide ion.[2]
(c) Calculate the total number of protons and the total number of electrons in a sulfate ion, SO42−.[2]
(d) An iron ion has 26 protons, 30 neutrons and a relative charge of 3+.
How many electrons does the ion have?[1]
Show the answer and mark scheme
(a) Answer: 3+
  • 3+ / +3
(b) Answer: 10
  • 8 + 1 = 9 (electrons in the neutral atoms / total protons)
  • 9 + 1 = 10
(c) Answer: 48 protons and 50 electrons
  • protons = 16 + (4 × 8) = 48
  • electrons = 48 + 2 = 50
(d) Answer: 23
  • 23

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