Fig. 1 shows two atom cards used in a forensic investigation of white powder recovered from a warehouse. The cards identify magnesium and oxygen, the elemen...
Question 1 Report
Fig. 1 shows two atom cards used in a forensic investigation of white powder recovered from a warehouse. The cards identify magnesium and oxygen, the elements in magnesium oxide. A student uses the proton number to decide which card belongs to each atom. Magnesium oxide is an ionic compound formed when magnesium transfers electrons to oxygen. The relative charge shown on each ion card must add to zero in the final compound.
(a) Name the element on card J. [1]
(b) Name the element on card K. [1]
(c) Give the charge on the magnesium ion formed. [1]
(d) Complete the formula of magnesium oxide: Mg___ . [1]
(e) Suggest why oxygen gains electrons in this reaction. [1]
(f) Give the number of electrons in an oxide ion. [1]
Answer Details
(a) Card J is magnesium, because magnesium has 12 protons. [1]
(b) Card K is oxygen, because oxygen has 8 protons. [1]
(c) Magnesium loses two outer electrons to form a 2+ ion, \(\mathrm{Mg^{2+}}\). [1]
(d) The charges \(\mathrm{Mg^{2+}}\) and \(\mathrm{O^{2-}}\) balance in a 1:1 ratio, so the formula is \(\mathrm{MgO}\). [1]
(e) Oxygen gains electrons to obtain a full outer shell and a stable electron arrangement. [1]
(f) An oxide ion has gained two electrons compared with a neutral oxygen atom, so it has 10 electrons. [1]
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