There are four elements 'p', 'q', 'r' and 's' having atomic numbers Z-1, Z, Z+1 and Z+2 respectively. If the element 'q' is an inert gas, select the correct answers from the following statements. (i) 'p' has most negative electron gain enthalpy in the respective period. (ii) 'r' is an alkali metal (iii) 's' exists in +2 oxidation state.