(iii) Explain the relationship between the number of valency electrons and the valency:for the elements Na to Al,.............................................................................................................................................for the elements P to Cl. .....................................(b) Across a period, the elements change from metallic to non-metallic.(i) Describe how the type of oxide changes across this period.(ii) Describe how the type of bonding in the chlorides formed by these elements changes across this period

(iii) The relationship between the number of valency electrons and the valency for the elements Na to Al is direct. Sodium (Na) has 1 valency electron and a valency of 1. Magnesium (Mg) has 2 valency electrons and a valency of 2. Aluminum (Al) has 3 valency electrons and a valency of 3.

For the elements Phosphorus (P) to Chlorine (Cl), the relationship is inverse. Phosphorus has 5 valency electrons and a valency of -3 (it needs 3 more electrons to complete its outer shell). Sulfur (S) has 6 valency electrons and a valency of -2. Chlorine (Cl) has 7 valency electrons and a valency of -1.

(b) (i) As we move across a period from left to right, the type of oxide changes from basic to acidic. Sodium (Na) forms a basic oxide (Na2O), while Aluminum (Al) forms an amphoteric oxide (Al2O3), which has both acidic and basic properties. Phosphorus (P), Sulfur (S), and Chlorine (Cl) form acidic oxides (P4O10, SO3, and Cl2O7 respectively).

(ii) The type of bonding in the chlorides formed by these elements changes across this period from ionic to covalent. Sodium chloride (NaCl) has ionic bonding, while Aluminum chloride (AlCl3) has a mix of ionic and covalent bonding. Phosphorus trichloride (PCl3), Sulfur dichloride (SCl2), and Chlorine (Cl2) have covalent bonding.