Subject: Inorganic Chemistry · Chapter: Main Group Elements · Topic: Main Group Elements – General · Exam: CSIR-NET 2020 · Marks: 2 · Difficulty: Medium
Correct statement/s among the following with respect to ionization energy (IE) is/are(i) $(\mathrm{IE_1}+\mathrm{IE_2}+\mathrm{IE_3})$ for indium is more than that of aluminium(ii) $\mathrm{IE_1}$ of scandium is higher than that of cobalt(iii) $\mathrm{IE_1}$ of gallium is lower than that of selenium(iv) $\mathrm{IE_1}$ of nitrogen is greater than that of oxygen
(a)(ii) and (iv)
(b)(iii) and (iv)
(c)(i) and (iv)
(d)(ii) and (iii)
Answer
Answer (as printed): B
Explanation
On moving down a group, the atomic radius generally increases. Even though a d-orbital is present in indium, its size is greater than that of aluminium, as the electron is added to the 5s orbital, which has a much higher size than the 3s orbital of aluminium. Even after contraction, the size of the 5s orbital is greater than that of the 3s orbital. Due to the higher atomic radius of In, its outer electrons experience lesser attraction towards the nucleus, hence $(IE_1+IE_2+IE_3)$ for In is less than that of Al. On moving along a period, size decreases, thus effective nuclear charge increases and hence I.E. increases. Therefore, $IE_1$ of Co is higher than that of Sc and $IE_1$ of Se is higher than that of Ga. Nitrogen has a stable half-filled $2s^{2}2p^{3}$ configuration, thus has a higher $IE_1$ than that of oxygen.