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

Options

A. `""_(26)^(56)Fe^(3+)`
B. `""_(26)^(56)Fe^(2+)`
C. `""_(27)^(56)Co^(2+)`
D. `""_(27)^(58)Co^(3+)`

Answer

A

Explanation

Let the number of protons(p) = x
`therefore`" "Number of electrons (e) = x - 3 (because the ion carries 3 units of positive charge, it will have 3 electrons less than the number of protons.)
Number of neutron(n)
`=(x-3)+((x-3)30.4)/100=(100(x-3)+(x-3)30.4)/100
n=(100x-300+30.4x-91.2)/100=(130.4x-391.2)/100`
We know that A = p + n
`56=x+(130.4x-391.2)/100
0r" "56=(100x-130.4x-391.2)/100
or" "5600=230.4x-391.2 or 5600 + 391.2 = 230.4x
or" "5991.2 = 230.4x
therefore" "x=5991.2/230.4=26`
Thus, number of protons (p) =26,
number of electrons (e) = 26 - 3 = 23.
Therefore, symbol of the ion is `._(26)^(56)Fe^(3+)`.