Question

The monatomic ions of Groups 1A(1) and 7A(17) are all singly charged. In what major way do they differ? Why?

Short answer

The Group$1\mathrm{A}\left(1\right)$ metals generate monocations, and the Group$7\mathrm{A}\left(17\right)$ nonmetals generate mono-anions.

Step-by-step solution

Write the elements in Group 1A(1) and Group 7A(17)

The elements in Group$1\mathrm{A}\left(1\right)$ are metal while the elements in Grouprole="math" localid="1656591865204" $7\mathrm{A}\left(17\right)$ are non-metals. Grouprole="math" localid="1656591826381" $1\mathrm{A}\left(1\right)$ elements are lithium (Li), sodium (Na), potassium (K), rubidium (Rb), caesium (Cs), and francium (Fr). These are also called alkali metals. Group$7\mathrm{A}\left(17\right)$ elements are fluorine (F), chlorine (Cl), bromine (Br), iodine (I), and astatine (At). These are commonly known as halogens.

Formation of ions.

The elements in Group $\mathbf{1}\mathbf{A}\mathbf{\left(}\mathbf{1}\mathbf{\right)}\mathbf{}$ always form monoatomic cationsby losing their single valence electron, resulting in the generation of a single positive charge on them (for example${\mathbf{Li}}^{\mathbf{+}}$,) while the elements of Group $\mathbf{}\mathbf{7}\mathbf{A}\mathbf{\left(}\mathbf{17}\mathbf{\right)}\mathbf{}$ form monoatomic anions by gaining a single valence electron from their counterparts, resulting in the generation of a single negative charge on them (for example, $\mathbf{F}$).