Question

(i) Write the electronic configuration of the following ions:

(a) He⁺ (b) Mg²⁺ (c) O²⁻ (d) S²⁻

(ii) What are the atomic numbers of elements whose outermost electrons are represented by:

(a) 3s² (b) 2p⁵ and (c) 2s¹

(iii) which atoms are indicated by the following configurations?

(a) [He]2s² (b) [Ne]3s²3p⁵ (c) [Ar]4s²3d⁵

Answer 1

(a) He⁺∶ Number of electrons = 2 − 1 = 1

\(\therefore\) Electronic configuration = 1s¹

(b) Mg²⁺:Number of electrons = 12 − 2 = 10

\(\therefore\) Electronic configuration = 2,8, = 1s² , 2s² , 2p⁶

(c) O²⁻:Number or electrons = 8 + 2 = 10

\(\therefore\) Electronic Configuration = 2, 8 = 1s² , 2s²2p⁶

(d) S²⁻∶ Number of electrons = 16 + 2 = 18

\(\therefore\) Electronic of Configuration = 2, 8, 8 = 1s² , 2s²2p⁶ , 3s²3p⁶

(ii) (a) 3s² , Atomic number of elements = 12

(b) For 2p⁵ , Atomic number of elements = 9

(c) For 2s¹ , Atomic number of elements = 3

(iii) 

Electronic	Atomic No.	Atom Configuration
(a) [He]2s2	4	Be
(b) [Ne]3s23p5	17	Cl
(c) [Ar]4s23d5	25	Mn