Question

an ion wih mass no. 56 contains 3 units of positive charge and 30.4% more neutrons than electrons assign the symbol for ion

Answer 1

Fe^3+ is the symbol of ion.
Mass no. of iron is 56
It is given that is contains 3 units of positive charge. So symbol is Fe3+

Answer 2

$\fbox\textcolor{orange}{\texttt{Answer = Fe(56,26)}}$

$\textcolor{indigo}{\texttt{Explanation :-}}$

Suppose number of electrons in the ion : $M^3+ \:=\:x$

No. of neutrons = $x+\frac{30.4}{100}\times{x}\:=\:1.304x$

No. of electrons in the neutral atom = $x\:+\:3$

No. of protons = $x\:+\:3$

Mass no. = No. of protons + No. of neutrons

$56=x+3+1.304x$

$2.304x=53$

Therefore, $x= \frac{53}{2.304}=23$

No. of protons = Atomic no. = $x+3=23+3=\texttt{26}$

Hence, the symbol of the ion is :

$\fbox{^{56}_{26}Fe^{3+}}$