Consider the following electron configurations to answer the question.(i)   1s²2s²2p⁶3s²3p⁶4s²3d¹⁰4p⁶5s¹
(ii)   1s²2s²2p⁶3s²3p⁵
(iii)   1s²2s²2p⁶3s²3p⁶4s²3d⁸
(iv)   1s²2s²2p⁶3s²3p⁶4s²3d¹⁰4p⁶
(v)   1s²2s²2p⁴3s¹
Which represents the ground state electron configuration for a halogen?

• A. (i)
• B. (ii)
• C. (iii)
• D. (iv)
• E. (v)

Answer: (B)

Verified step by step guidance

1. Understand that halogens are elements in Group 17 of the periodic table, characterized by having seven electrons in their outermost shell.
2. Review the electron configurations provided and identify the one that corresponds to a halogen. A halogen will have an electron configuration ending in 'p5', indicating five electrons in the p orbital of the outermost shell.
3. Examine each electron configuration: (i) ends in 5s1, (ii) ends in 3p5, (iii) ends in 3d8, (iv) ends in 4p6, and (v) ends in 3s1.
4. Recognize that configuration (ii) 1s2 2s2 2p6 3s2 3p5 matches the characteristic ending of a halogen, with the outermost p orbital containing five electrons.
5. Conclude that configuration (ii) represents the ground state electron configuration for a halogen, specifically chlorine, which is in the third period and Group 17.