Identify the Mg2+ ion from the Fig.4.1, where n and p represent the number of neutrons and protons respectively.

AcademicChemistryNCERTClass 9

Correct Answer: (d)

Explanation:  Atomic number (Z) of magnesium is 12

Mass number (A) is 24 ( as p = 12, n = A - Z = 24 - 12 = 12 ).

Electronic configuration of Mg atom is 2, 8, 2.

Electronic configuration of  Mg 2+ion is 2, 8 (the positive charge is due to the loss of 2 electrons). 

The number of protons and the number of neutrons inside the magnesium atom remain unaffected by the formation of a magnesium ion by the magnesium atom. 

Option (B) and Option (C) do not represent the number of neutrons (n) and the number of protons (p) correctly.

Option (A) represents Mg atom but not Mg 2+ion.

Updated on 10-Oct-2022 13:32:09