When chemicals react with each other which factors decide that a successful reaction has taken place ?

The factors that affect the rate of a reaction are:

nature of the reactant - when reactants with different chemical composition are exposed to same conditions they would react differently.  For instance, when an acid or base is added on litmus paper, blue litmus paper turns red in presence of acid while red litmus paper turns blue when base is added.surface area- a compound with small pieces spread over a large area will react faster than a big lump of a compound occupying a small area.temperature of reaction- reactants would react faster at high temperatures. this is because they have higher kinetic energy to collide with each other. Hence a plate of food on the table spoils faster than a plate of food in the fridge.concentration- an increase in concentration leads to more molecules available to collide and form products. An example, when you add more of indicator in a solution, the color becomes more clear since more particles react to give more color.presence of a catalyst- a catalyst lowers the activation energy, which means less energy is required to shift reaction in forward direction. In the presence of iron (Fe) a catalyst, nitrogen N₂ and hydrogen H₂ react to produce NH₃

Ithink 2 is the correct

You use the atomic number to find out how many protons and neutrons there are in the atom. you use the atomic mass to find out how many protons and electrons there are in the atom.