What is the difference between atomic number and atomic mass, and what do they tell you about the atom

Mass number is the number of protons and neutrons in an atom, and it tells us about the mass of the atom in amu, or atomic mass units.

Atomic mass is the average mass of all the isotopes of a certain type

2fe + 3h2so4 -> fe2(so4)3 + 3h2

it is necessary to balance equations in order to get the proper amount of reactants as well as products in order not to make a miscalculation.

you cannot change the subscripts as that would change the substance itself. for instance, diatomic elements such as h2 only have the subscript two when a gas. another example would be so4, if you were to change the subscript, the element would no longer be sulfate.

we change the coefficients instead as that only changes the number of molecules rather than the substance itself.

hope this !