Question

*Which of the following isoelectronic species has the smallest size?*

1️⃣ N³⁻
2️⃣ O²⁻
3️⃣ Al³⁻
4️⃣ All have equal size​

Answer 1

The correct option is 2:
All the species in the option are isoelectronic.
Isoelectronic species are those species which have same number of electrons.
Talking about the size , we know that the size of elements decreases from left to right in a period.
Hence O2- will have smallest size.
Talking about Al3- it's size is greater than other elements because it is present below Boron and we know that in a group size increases , down the group.
Hence, option 2 is the correct answer.

Answer 2

Answer:

The correct answer to the question-*Which of the following is electronic species has the smallest size?* is-

2️⃣ O²⁻

Explanation:

N³⁻,O²⁻, Al³⁻are all isoelectronic species.

Isoelectronic species

Isoelectronic species refers to those two atoms, ions or molecules that have the same number of valence electrons  and same electronic structure . Isoelectronic chemical species shows similar chemical properties.

Talking about the size , we know that the size of elements decreases from left to right in a period.

Therefore, O²⁻ will have smallest size.

In Al³⁻  ,it's size is greater than other elements as it is present under Boron and we know that in a group ,size increases as we move down the group.

Therefore, option 2️⃣ O²⁻ is the correct answer.