Answer:
2Na + I2= 2NaI
Explanation:
Sodium molecule has a valency of 1 and iodine valency of 1. Iodine is a type of halogen with atomic number 53. However, when two molecules of iodine combine they form a gas molecule with a valency of 2. The two iodide atoms combine together by covalent bonds to form iodine gas. When the two molecules react together only one molecule of iodine is used to complete the reaction. The two added before the reactants and the products balances the reaction.
The 2 that is added before the product formed is used to balance the number of atoms that have reacted. 2 iodide atoms in the reactants were used and therefore 2 iodide atoms in the product were formed. This makes the number of Na formed to be 2 and therefore 2 is added in the reacting Na molecule.
