In a chemical formula, the number of atoms for each element is usually indicated by a

Subscript

Explanation:

For example shows 1 atom of Ca and 2 atoms of Cl

Another example

we multiply

Coefficient × subscript × number outside the bracket.......... to find the number of atoms  

(Please note: 3 is the coefficient, and if there is no number given then 1 will be the coefficient )

So,

, Ca atoms

, P atoms

, O atoms are present.

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