Atomic Structure | Chapter 12 | 8th Science - Chemical formula or Molecular formula | 8th Science : Chapter 12 : Atomic Structure
Chapter: 8th Science : Chapter 12 : Atomic Structure
Chemical formula or Molecular formula
Chemical formula or Molecular
formula
Chemical formula is the shorthand
notation of a molecule (compound) . It shows the actual number of atoms of each
element present in a molecule of a substance. Certain steps are followed to
write down the chemical formula of a substance. They are given below.
Step1: Write
down the symbols of elements/ ions side by side so that the positive radical is
on the left and the negative radical is on the right hand side.
Step2: Write
the valencies of the two radicals above their symbols to the right in
superscript (Signs ‘+’ and ‘-’ of the ions are omitted) .
Step3: Reduce
the valencies to simplest ratio if needed. Otherwise interchange the valencies
of the elements/ions. Write these numbers as subscripts. However, ‘1’ appearing
on the superscript of the symbol is omitted.
Thus, we arrive the chemical formula
of the compound.
Let us derive the chemical formula
for calcium chloride.
Step
1: Write the symbols of calcium and
chlorine side by side. Ca Cl
Step
2: Write the valencies of calcium and
chlorine above their symbols to the right. Ca2 Cl1
Step
3:
Interchange the valencies of elements. Ca Cl2
Thus the chemical formula for
calcium chloride is CaCl2
Activity 3
Write the chemical
formula of the compounds
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