An isotope has more or less in the nucleus.

Neutrons

Explanation:

An isotope has more or less number of neutrons in the nucleus.

The nucleus of an atom is made up of two fundamental particles, the protons and the neutrons. Protons are positively charged particles in an atom. Neutrons do not carry any charges whatsoever.

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 !

i'm pretty sure its b i might be wrong though!