Why group 1 element is larger ionic?

Group 1 elements, known as alkali metals, have larger ionic radii compared to other elements because they possess a single valence electron in their outermost shell. When they form ions, they lose this electron, resulting in a positively charged ion (cation) that has fewer electron-electron repulsions and a larger radius. Additionally, the presence of only one electron in the outer shell means that the effective nuclear charge felt by the remaining electrons is relatively low, allowing the ion to maintain a larger size.