Answer
(a) Sodium loses an electron to to obtain a stable configuration and form a $Na^{+}$ cation
Na to $Na^{+}$ + $1e^{-}$
(b) Oxygen atom acquires 2 electrons to obtain a stable configuration and form a $O^{2-}$ anion
O + $2e^{-}$ to $O^{2-}$
(c) Calcium loses 2 electrons to obtain a stable configuration and form a $Ca^{2+}$ cation
Ca to $Ca^{2+}$ + $2e^{-}$
(d) Chlorine obtains a 1 electron to obtain a stable configuration and form a $Cl^{-}$ anion
Cl + $1e^{-}$ to $Cl^{-}$
Work Step by Step
(a) Sodium loses an electron to to obtain a stable configuration and form a $Na^{+}$ cation
Na to $Na^{+}$ + $1e^{-}$
(b) Oxygen atom acquires 2 electrons to obtain a stable configuration and form a $O^{2-}$ anion
O + $2e^{-}$ to $O^{2-}$
(c) Calcium loses 2 electrons to obtain a stable configuration and form a $Ca^{2+}$ cation
Ca to $Ca^{2+}$ + $2e^{-}$
(d) Chlorine obtains a 1 electron to obtain a stable configuration and form a $Cl^{-}$ anion
Cl + $1e^{-}$ to $Cl^{-}$
