Question 23 of 62intermediate🔧 ApplyShort Answer3 marks

(i) Write the electronic configurations of the following ions: (a) H⁻ (b) Na⁺ (c) O²⁻ (d) F⁻ (ii) What are the atomic numbers of elements whose outermost electrons are represented by (a) 3s¹ (b) 2p³ and (c) 3p⁵? (iii) Which atoms are indicated by the following configurations? (a) [He] 2s¹ (b) [Ne] 3s² 3p³ (c) [Ar] 4s² 3d¹.

(i)
Answer

(a) H⁻: 1s21s^2 (b) Na⁺: 1s22s22p61s^2 2s^2 2p^6 (c) O²⁻: 1s22s22p61s^2 2s^2 2p^6 (d) F⁻: 1s22s22p61s^2 2s^2 2p^6

(ii)
Answer

(a) For outermost electron 3s¹, the configuration is [Ne] 3s13s^1. Total electrons = 10 + 1 = 11. (b) For 2p³, the configuration is [He] 2s22p32s^2 2p^3. Total electrons = 2 + 2 + 3 = 7. (c) For 3p⁵, the configuration is [Ne] 3s23p53s^2 3p^5. Total electrons = 10 + 2 + 5 = 17.

(iii)
Answer

(a) [He] 2s12s^1 has 3 electrons, indicating Lithium (Li). (b) [Ne] 3s23p33s^2 3p^3 has 15 electrons, indicating Phosphorus (P). (c) [Ar] 4s23d14s^2 3d^1 has 21 electrons, indicating Scandium (Sc).

Explanation

The electronic configurations are determined by the total number of electrons in the ion or atom. For ions, electrons are added or removed based on the charge. The atomic numbers are found by summing the electrons in the given outermost configuration along with the core electrons (like [Ne] or [He]).

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