Question

list the following ions in order of increasing ionic radius: sr^{2 +}, rb^{+}, as^{3 -}, se^{2 -}, br^{-}

Explanation:

Step1: Consider is - electronic species

These ions ($Sr^{2 + },Rb^{+},As^{3 - },Se^{2 - },Br^{-}$) are is - electronic (have the same number of electrons).

Step2: Apply the rule of ionic radius for is - electronic species

For is - electronic species, the ionic radius increases with an increase in the negative charge and decreases with an increase in the positive charge.

Step3: Analyze the charges

$Sr^{2+}$ has a + 2 charge, $Rb^{+}$ has a + 1 charge, $As^{3 - }$ has a - 3 charge, $Se^{2 - }$ has a - 2 charge and $Br^{-}$ has a - 1 charge.

Answer:

$Sr^{2+}