What does the symbol ${{H}_{2}}$ convey?

Hint: Hydrogen is an element which is having atomic number 1. It is the lightest element in the periodic table. As we know that it is the most abundant substance present in the universe, that basically comprises about 75% of baryonic mass.

Complete answer:
- We can say that the symbol ${{H}_{2}}$ conveys molecular hydrogen that has two hydrogen atoms.
- There are several properties of dihydrogen like:
- ${{H}_{2}}$ is highly flammable, it is found to form explosive mixtures with air and chlorine. The reactions can be triggered by sunlight or heat. The pure flame of hydrogen-oxygen also emits ultraviolet light.
- ${{H}_{2}}$ is basically unreactive, due to the very strong H-H bond present . It is found that ${{H}_{2}}$ mainly form compounds with the elements that are electronegative, such as it reacts with fluorine and chlorine to form hydrogen fluoride and hydrogen chloride. Basically by the presence of metal catalysts, its reactivity is strongly affected.
- ${{H}_{2}}$is found to occur in various phases like gaseous hydrogen, slush hydrogen, solid hydrogen, liquid hydrogen, metallic hydrogen.
- As we know that ${{H}_{2}}$ is a product in some types of anaerobic reactions which is produced by several microorganisms, basically through the reactions that are catalysed by hydrogenases ( that are nickel or iron containing enzymes).

- Hence, we can say that the symbol ${{H}_{2}}$ conveys two hydrogen atoms that are bonded together by a single bond.

Note: -${{H}_{2}}$ should not be confused with 2H. As, ${{H}_{2}}$ consists of two hydrogen atoms that are bonded together by a single bond or we can say it is a molecule of hydrogen. Whereas, 2H signifies two moles of elemental hydrogen, which is not bonded to anything