posted by Maria
what is the difference between an atom and an ion ???
In an atom, the number of electrons is equal to the number of protons. In an ion, the number of electrons is not equal to the number of neutrons. A positive ion has more protons than electrons whilst a negative ion has more electrons than protons.
Another way of looking at it--an ion is an atom (sometimes more than one atom) with a + or - charge on it.
example of one atom--Na atom; Na^+ ion
examle of more than one atom--SO4^2-