Which of Na+ and Mg2+ is the smaller ion. Explain your answer. (2 marks)

Mg2+ is the smaller ion. (1 mark) Mg2+ has a larger nuclear charge than Na+ and has the same number of electrons. (1 mark)

Further explaination: Magnesium is further along the period than sodium is which means that the electrostatic attraction between the valence electrons and the nucleus is greater than that of sodium and the relative nuclear charge for a 2+ ion is larger than that of a 1+ ion.