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Model Paper 5 — Chemistry STD 11 Science — Question

Rajasthan BoardEnglish MediumSTD 11 ScienceChemistryModel Paper 51 Mark
MCQ
An anion $A ^{3-}$ has 18 electrons. Write the atomic number of A.
  • A
    24
  • B
    21
  • C
    12
  • ✓
    15
✓

Answer

Correct option: D.
15
(d) 15
Explanation: $A ^{3-}$ means it has got an additional 3 electrons. The atomic number is the number of electrons in a neutral atom.
Therefore atomic number $=18-3=15$.

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