Question

between a neutral atom and its cation which has bigger size ?

Answer 1

Nucleus of an atom is positively charged & electrons are revolving around the nucleus in their respective orbitals.The more the cations or anions comes closer to the nucleus ,lesser will be their atomic radii. Therefore in the case of cations & anions are as follows:

A cation is a positively charged species that  has a fewer number of electrons than its parent atom, while its nuclear charge remains the same. As a result, the attraction of electrons to the nucleus is more in a cation than in its parent atom. Therefore, a cation is smaller in size than its parent atom.

On the other hand, an anion is a positively charged species that  has one or more electrons than its parent atom, resulting in an increased repulsion among the electrons and a decrease in the effective nuclear charge. As a result, the distance between the valence electrons and the nucleus is more in anions than in it’s the parent atom. Hence, an anion is larger in radius than its parent atom.

Answer 2

Between a neutral atom and its cation which has bigger size  neutral atom will have bigger size because in order to form a cation an atom will have to lose an electron 

as the atom will lose electron the nucleus can hold its electrons more tightly which will decrease the size