3. Cl will form ionic compound by gaining one electron from the cation.
Explanation:
The chloride ion can be formed by gaining an electron during ionic bond formation.
Chlorine has 7 electrons in its outermost shell thereby requiring only 1 electron to complete its octet.
Electronic configuration of chlorine is 1S2,2S2,2P6.3S2,3P5
Chloride is an anion formed when chlorine element gains an electron or when compound like NaCl dissolves in water Sodium ions (cation) and chloride ions(anion) is formed.
In ionic compounds only electrons take part ie they move from one atom to another.