The formation of an ionic bond involves the

Answer is: transfer of electrons.

Ionic bond is the electrostatic attraction between oppositely charged ions.  

For example, compound magnesium chloride (MgCl₂) has ionic bond.

Magnesium (Mg) transfers two electrons, became positive cation, to chlorine (Cl), which became negative anion.

Magnesium is metal from group 2 and chlorine is nonmetal from group 17 of the Periodic table.

what is the volume occupied by 40 grams of argon gas (ar) at standard conditions? what volume, in liters, is occupied by 1.5 x 1023