Question

pick the larger species from each of the following pairs.
match the words in the left column to the appropriate blanks in the sentences on the right.
li
between li and li⁺, the larger species is
li⁺
between i⁻ and cs⁺, the larger species is
i⁻
between mo and mo³⁺, the larger species is
cs⁺
between o and o²⁻, the larger species is
mo
mo³⁺
o
o²⁻

Explanation:

Step1: Compare \(Li\) and \(Li^{+}\)

When an atom loses an electron to form a cation (\(Li^{+}\) here), the remaining electrons are more strongly attracted to the nucleus (due to the same nuclear charge but fewer electrons). So, \(Li\) is larger than \(Li^{+}\).

Step2: Compare \(I^{-}\) and \(Cs^{+}\)

\(I^{-}\) has an extra electron (compared to neutral \(I\)), increasing electron - electron repulsion and making it larger. \(Cs^{+}\) has lost an electron. Also, considering their positions in the periodic table, \(I^{-}\) (in the p - block, larger atomic radius trend) and \(Cs^{+}\) (in the s - block, but cation). \(I^{-}\) is larger.

Step3: Compare \(Mo\) and \(Mo^{3+}\)

Similar to the \(Li/Li^{+}\) case. When \(Mo\) loses 3 electrons to form \(Mo^{3+}\), the remaining electrons are more tightly held by the nucleus. So, \(Mo\) is larger.

Step4: Compare \(O\) and \(O^{2 -}\)

\(O^{2-}\) has two extra electrons. The increased electron - electron repulsion (for the same nuclear charge) causes \(O^{2-}\) to expand. So, \(O^{2-}\) is larger.

Answer:

Between \(Li\) and \(Li^{+}\), the larger species is \(Li\).
Between \(I^{-}\) and \(Cs^{+}\), the larger species is \(I^{-}\).
Between \(Mo\) and \(Mo^{3+}\), the larger species is \(Mo\).
Between \(O\) and \(O^{2-}\), the larger species is \(O^{2-}\).