Question

The actual cation radii are Y3+ = 104 pm, Nb3+ = 86 pm, and Sb3+ = 90 pm. Explain this trend. (Hint: You should consider the electron configurations!) [

Answer 1

Cations with larger charges are smaller than cations with smaller charges. Proceeding down the groups of the periodic table, we find that cations of successive elements with the same charge generally have larger radii, corresponding to an increase in the principal quantum number, n.

Step-by-step explanation:

Cations with larger charges are smaller than cations with smaller charges. Proceeding down the groups of the periodic table, we find that cations of successive elements with the same charge generally have larger radii, corresponding to an increase in the principal quantum number, n.

For example, Y3+ has a larger charge than Nb3+ and Sb3+, so its cation radius is smaller. Nb3+ has a larger charge than Sb3+, so its cation radius is also smaller.

This trend can be explained by considering the electron configurations of the cations. As you move down the periodic table, the principal quantum number, n, increases, which means electrons are being added to regions of space that are increasingly distant from the nucleus. This leads to an increase in the size of the atom and its cation radius.

Answer 2

Step-by-step explanation:

Atomic radius of an atom is defined as the total distance from the nucleus to the outermost shell of the atom.

An ion is formed when a neutral atom looses or gains electrons.

When an atom looses electrons, it results in the formation of positive ion known as cation.

When an atom gains electrons, it results in the formation of negative ion known as anion.

As moving from left to right in a period, more and more electrons get added up in the same shell and the attraction between the last electron and nucleus increases, which results in the shrinkage of size of an atom. Hence, the size of an atom decreases.

The size of the cation is small then their neutral atom because it has less number of electrons while its nuclear charge remains the same. Thus, the nucleus attracts the electron more towards itself and leads to the decrease in size.

We are given three cations:
`Y^(3+),Nb^(3+)\text{ and}Sb^(3+)`

Yttrium lies in Period 5, group 3 of the periodic table.

Electronic configuration of Yttrium

`1s^22s^22p^63s^23p^63d^(10)4s^24p^64d^15s^2`

Niobium lie in Period 5, group 5 of the periodic table.

Electronic configuration of Niobium

`1s^22s^22p^63s^23p^63d^(10)4s^24p^64d^45s^2`

Antimony lies in Period 5, group 15 of the periodic table.

Electronic configuration of Antimony

`1s^22s^22p^63s^23p^63d^(10)4s^24p^64d^(10)5s^25p^3`

So, the order of atomic radii in increasing order follows:

`Sb^(3+)<Nb^(3+)<Y^(3+)`

Hence, antimony ion is the smallest and yttrium ion is the largest.