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MCQ practice · SSC Chemistry Board questions · Chapter 3: Structure of Matter

Dinajpur Board 2022

In the ion ⁷₃Li⁺:

  1. i. Number of neutrons 4
  2. ii. Number of protons 4
  3. iii. Number of electrons 2

Think it through first, then pick an option.

  1. a i
  2. b iii
  3. c i and iii
  4. d i, ii and iii
Answer and explanation

Correct answer: c i and iii

Neutrons 7 − 3 = 4 and electrons 3 − 1 = 2 are right; protons are 3, not 4.

Why the other options are wrong

  • a i: iii is also true: Li⁺ has 3 − 1 = 2 electrons.
  • b iii: i is also true: neutrons = 7 − 3 = 4.
  • d i, ii and iii: ii is false: lithium has 3 protons, and keeps 3 as an ion.