Question

Smallest cation and smallest anion are respectively:
1.${H^ + }$ and ${H^ - }$
2.${H^ + }$ and ${F^ - }$
3.$L{i^ + }$ and ${H^ - }$
4.$L{i^ + }$ and ${F^ - }$

Answer 1

Hint: We can say that the atomic radius could be described as the shortest distance among the nuclei of an atom and its valence shell of the atom. We could say that atomic radius could be measured by x-ray and several other spectroscopy techniques. In a constant pattern, we can say that in the periodic table the atomic radii of the elements could vary.

Complete answer:
We can say that as we move across the period, there would be decrease in atomic radii and when we move from top to bottom in a group, there would increase in atomic radii. The reason is because the outermost electrons are found in the same valence shell in periods. There would be an increase in atomic number inside the same period whereas moving from left to right would increase in the effective nuclear charge. The atomic radii of the elements would decrease when there is an increase in attractive forces.
Among the given options, we can say that the smallest cation is ${H^ + }$ and the smallest anion is ${F^ - }$. The reason why the smallest anion is ${F^ - }$is because on moving across the periods, the size could reduce from left to right whereas we move down the group. As the number of protons increases, the attraction of electrons also gets increased and they are moved closer to the nucleus. This leads to a smaller size of ion/atom.
The reason why hydrogen ions are the smallest cation is because hydrogen contains one electron in the valence shell once it loses electron, it becomes ${F^ - }$.
We can conclude that the smallest cation is ${H^ + }$ and the smallest anion is ${F^ - }$.

Option (2) is correct.

Note:
We can say that atomic radius could be defined by four basic definitions. They are van der Waals radius, metallic radius, covalent radius, and ionic radius. We have to know that atomic radii of isolated neutral atoms could be found in the range of thirty-three hundred pm. We have to remember that factors which affect atomic radii are shielding, nuclear charge, and electron shells.