Elephants are really cool
According to Arrhenius theory of acid and bases, an acid is a proton donor, while base donates hydroxyl ions. Further, acid and base reacts to form salt and water.
Consider following example.
HCl + H2O → Cl- + H3O+
here, HCl has donated a proton, hence it is an acid.
Now consider following reactionHCl + NaOH ↔ NaCl + H2O
in this reaction, HCl donates proton, hence it is acid. On other hand, NaOH donates hydroxyl ion (i.e. OH-), hence it is a base.
We need to dilute 0.400 mol of copper (II) sulfate, how do we know, how many weigh of

we have to dilute??
It's simple.

Using a periodic table we can find the molar mass of


Then

now we can replace it


Then we have to dilute 63.84 grams of copper (II) sulfate in 1 L of water to obtain a solution with 0.400M
This is a short answer but because they have the same amount of protons and electrons but different amount of neutron