(i) Bond angle of NH 3 = 107°

PH 3 > AsH 3 = 90°

According to bond angle the %s character of Ip in NH 3 = 22% while in PH 3 & AsH 3 having approximately 100%, so the donation of Ip in PH 3 & AsH 3 are difficult. Hence, the acidic character increases and the order of acidic character is NH 3 < PH 3 < AsH 3 is correct

(ii) On moving left to right in a period ionisation energy increases. Li < Be < B < C but the first ionisation potential of Be is higher than that of B because Be has fulfilled configuration.

(iii) Metallic character increases hence the basic character of oxide increases.

(iv) In a group from top to the bottom, the number of the shell increases hence radius increases.