Question

What is the 2 in ${\mathrm{H}}_2\mathrm{O}$ called?

Answer 1

1. ${\mathrm{H}}_2\mathrm{O}$ is the chemical formula of water.
2. 2 atoms of Hydrogen and 1 atom of Oxygen comprises to form the water molecule.
3. To show the two atoms of Hydrogen we use subscript 2.
4. The valency of Oxygen in a water molecule is 2.
5. Valency is defined as the total number of molecules present in the outermost shell of an atom to combine or displace another atom for bond formation.
6. The bonding present in a water molecule is Hydrogen bonding.
7. The Hydrogen bonding is shown below:
   
8. The chemical reaction occur as follows.
   $2{\mathrm{H}}_2\left(\mathrm{g}\right)+{\mathrm{O}}_2\left(\mathrm{g}\right)\to 2{\mathrm{H}}_2\mathrm{O}\left(\mathrm{l}\right)$