An atom with two valence electrons in the periodic table belongs to the alkaline earth metals or 2nd group. The element with atomic number 17 is chlorine with 7 valence electrons. Ionic compounds are formed between the atoms of elements with high electronegativity difference. More the difference, more they are likely to form ionic bond.
Thus in this case, the most likely formed ionic compound will be with alkaline earth metal with high electropositivity. The highest electropositive element in group 2 is barium thus, ionic compound formed will be [tex]BaCl_{2}[/tex]
In [tex]BaCl_{2}[/tex], barium will donate its two electrons, one to each chlorine atom. The resultant compound will be ionic in which all the atom have complete octets.
