Bonding and structure — practice questions

Magnesium has a giant metallic structure. [1] It consists of a lattice of $Mg^{2+}$ ions surrounded by a sea of delocalised electrons. [1] These electrons are mobile and free to move throughout the structure to carry charge. [1]

Sulfur has a simple molecular structure, existing as $S_8$ rings. [1] While there are strong covalent bonds within the molecules, there are only weak van der Waals' forces between the molecules. [1] There are no mobile charge carriers (free electrons or ions) to conduct electricity. [1]

Sodium Chloride (NaCl): Has a giant ionic lattice structure. [1] There are strong electrostatic forces of attraction between oppositely charged $Na^+$ and $Cl^-$ ions. [1] A large amount of energy is required to overcome these forces, resulting in a high melting point. [1]

Silicon Dioxide ($SiO_2$): Has a giant covalent (macromolecular) structure. [1] Each silicon atom is covalently bonded to 4 oxygen atoms, and each oxygen to 2 silicon atoms. [1] A very large amount of energy is needed to break these numerous strong covalent bonds, resulting in a very high melting point. [1]

Iodine ($I_2$): Has a simple molecular structure. [1] Within the $I_2$ molecules, there are strong covalent bonds. However, between the molecules, there are only weak van der Waals' forces. [1] Only a small amount of energy is needed to overcome these weak intermolecular forces, resulting in a low melting point. [1]