Ncert Exercises & Solutions

2.44 An ion with mass number 56 contains 3 units of positive charge and 30.4% more neutrons than electrons. Assign the symbol to this ion.

Let the number of electrons present in ion $A^{3 +}$ be x.
∴ Number of neutrons in it = x + 30.4% of x = 1.304 x

Since the ion is tripositive,

⇒ Number of electrons in neutral atom = x + 3
∴ Number of protons in neutral atom = x + 3

Given,

Mass number of the ion = 56

$∴ (x + 3) + (1.304 x) = 56$
$2.304 x = 53$
$x = \frac{53}{2.304} = 23$

∴ Number of protons = x + 3 = 23 + 3 = 26
∴ The symbol of the ion ${}_{26}^{56}{Fe}_{3 +}$ .