Question

how to write chemical formula

Answer 1

writing a chemical Equation is very easy just write the formulas of the reactants in the left side and products at the right side.This equation is called skeletal equation,after balancing it will give the required equation.

Answer 2

U hav to learn the short forms for the Elements. This can be done by going through the Periodic Table. Once u learn them, making a formula will be easy. :)

For eg- Say sodium reacts with Hydrochloric acid.

Sodium - Na (short form)

Hydrochloric acid - HCl  (Hydrogen + Chlorine) (H+ Cl)

then the reaction will be- Na+ HCl -----> NaCl (Sodium Chloride) Salt + H (Hydrogen gas)

this is the primary level of understanding. Hope u did. :)