Question

How to write the formula for Calcium carbonate by using the criss-cross method?

Answer 1

Writing the formula of Calcium carbonate

• Step 1: Identify the constituent elements

1. Calcium carbonate is an inorganic compound with constituent elements Calcium (Ca) Carbon (C) and Oxygen (O).
2. In this formula, Calcium is a cation while carbonate is an anion.
3. The formula of carbonate anion is ${{\mathrm{CO}}_3}^{2-}$.

• Step 2: Finding the valency of the constituent elements

1. Electronic configuration of Ca (20) = 2,8,8,2
   Number of valence electrons in Ca = 2
   Valency of Ca = +2
2. Valency of ${{\mathrm{CO}}_3}^{2-}$ = -2

• Step 3: Formation of Chemical formula

1. Using the criss-cross method
   $\underset{2}{\mathrm{Ca}}\underset{2}{C{O}_3}$

• The formula of the compound comes out to be ${\mathrm{CaCO}}_3$

Hence, the formula of Calcium carbonate comes out to be ${\mathrm{CaCO}}_3$.