Question

how are chemical reactions expressed in shortest way

Answer 1

when the compounds, reactants , products are written in symbolic form.

Answer 2

The shortest way to express chemical reactions is to make use of the element symbols.

EXPLANATION:

The chemical equations can be written by using the symbols of the elements which is involved to express chemical reactions in the shortest way. For example, the reaction of hydrogen and oxygen forms water is expressed as Hydrogen+ Oxygen $\rightarrow$ Water. This can be expressed in the shortest way by using symbols for hydrogen, oxygen and water as:

$\mathrm{H}_{2}+\mathrm{O}_{2} \rightarrow \mathrm{H}_{2} \mathrm{O}$