Fig. 17.1 Fig. 17.1 is a representation of the structure of a typical metal such as magnesium. [FIGURE] (a) Name the type of structure and bonding present i...

The figure for this question was not printed. The accepted model for the structure of a metal such as magnesium is a regular lattice of positive metal ions held together by a surrounding "sea" of delocalised electrons, shown below.

(a) The structure is a giant metallic structure (lattice) [1] and the bonding is metallic bonding [1].

(b) A metal consists of a regular, giant lattice of positive metal ions [1] surrounded by a "sea" of delocalised (mobile) electrons [1]; these electrons come from the outer shells of the atoms and are shared by, and free to move through, the whole structure [1].

(c) Because the delocalised electrons are free to move through the lattice [1], when a voltage is applied they drift and carry the electric current [1].

(d) When a force is applied the layers of positive ions slide over one another [1]; the electron sea moves with them so the metallic bonding is maintained, and the metal changes shape without shattering, which is why it is malleable [1].

(e) Metal atoms have a small number of outer-shell electrons [1] which they lose (release) easily to become the delocalised electron sea [1].

(f) Magnesium is in Group II, so each atom loses 2 electrons to give a 2+ ion, \(\text{Mg}^{2+}\) [1]; each atom therefore contributes 2 delocalised electrons [1] to the structure.

(g) Solid magnesium conducts electricity [1], but solid magnesium chloride does not [1]: in the metal the delocalised electrons are free to move, whereas in solid \(\text{MgCl}_2\) the ions are locked in fixed positions in the lattice and cannot move to carry charge [1].

(h) There is strong electrostatic attraction between the positive ions and the sea of delocalised electrons [1], and a large amount of energy is needed to overcome this attraction (break the metallic bonds), so metals generally have high melting points [1].