Passing electricity through compounds: electrolysis
2 marks · EasyHow many positive ions and how many negative ions are present in the formula unit of magnesium bromide ()? State the name for each type of ion.
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There is 1 Mg^{2+} cation (positive ion) and 2 Br^- anions (negative ions) in one formula unit of .
Also accept: 1 magnesium cation, 2 bromide anions
Common mistakes: Reversing anion and cation; Giving the atom instead of the ion
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Marking points
M1 · 1 mark · Recognises that Mg^{2+} is the cation (positive ion) and Br^- is the anion (negative ion).
A1 · 1 mark · Correctly counts: 1 cation and 2 anions per formula unit.
Worked solution
contains 1 magnesium ion (), which is a cation, and 2 bromide ions (), which are anions.