Chemistry PYQ 13 of 152 · Structure of Atom

The number of electrons and neutrons in an element is 18 and 20 respectively. Its mass number is -

  1. A22
  2. B2
  3. C38
  4. D20
  5. ENone of the above / More than one of the above

65th BPSC

Show answer and explanation

Correct answer: (c) 38

Explanation

Mass number (A) = number of protons + number of neutrons.

In a neutral atom, protons = electrons = 18, and neutrons = 20.

Therefore A = 18 + 20 = 38.

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