Ionic bonding in magnesium oxide
2 marks · EasyDraw a dot-and-cross diagram to show the electron arrangement in the Mg^{2+} ion. Use dots for magnesium's original electrons. Clearly show the charge.
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Must show: full electronic shell(s), no outer electrons (for Mg^{2+}), correct charge (2+) or Mg^{2+} label
Also accept: Accept 0 electrons in outer shell with two full inner shells drawn; Square brackets accepted for ion
Common mistakes: Showing outer electrons left on the ion
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Marking points
B1 · 1 mark · Correct arrangement: only inner 2,8 electrons shown, no outer electrons.
B1 · 1 mark · Charge shown as 2+ or Mg^{2+}.
Worked solution
Magnesium atom: 2,8,2 becomes Mg^{2+}: 2,8 (inner shells only).
Only two shells should be shown, and the ion charge indicated as 2+ or Mg^{2+}.