`Na^(+), Mg^(2+), Al^(3+)`, and `Si^(4+)` are isoelectronic ions. Their ionic size will follow the order

Options

A. `Na^(+) gt Mg^(2+) lt Al^(3+) lt Si^(4+)`
B. `Na^(+) lt Mg^(2+) gt Al^(3+) gt Si^(4+)`
C. `Na^(+) gt Mg^(2+) gt Al^(3+) gt Si^(4+)`
D. `Na^(+) lt Mg^(2+) lt Al^(3+) ltSi^(4+)`

Answer

C

Explanation

In isoelectronic species the number of electrons are same but nuclear charge is different. As the nuclear charge increase, the attraction force on last electron increases, so the size decreases or in other words .
`"Ionic size" prop(1)/("Charge oncation")`and hence, order is
`(Na^(+) gt Mg^(2+) gt Al^(3+) gt Si^(4+))/(("Nuclear charge increase")/("Size decrease"))`