Ionic bonding in magnesium oxide
2 marks · EasyA magnesium atom has 12 electrons and an oxide ion has 10 electrons. Calculate the total number of electrons present in one unit of magnesium oxide (MgO).
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22 (±0)
Common mistakes: Adding before the correct number of electrons are assigned to ions
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Marking points
M1 · 1 mark · States/processes that there are 12 electrons in Mg and 10 in O^{2-} (or vice versa).
A1 · 1 mark · Gives final answer of 22 electrons.
Worked solution
Mg atom has 12 electrons; O^{2-} ion has 10 electrons. 12 + 10 = 22 electrons in one unit of MgO.