What is nuclide notation referring to? Only the nucleus or the whole atom? sorry that this is an easy question but I am just a bit confused about nuclide notation. When you say e.g. $^{240}_{94}\text{Pu}$, are you referring to the atom of $\text{Pu}$ or only its nucleus?
It doesn't make this clear in my revision guide so I wanted to make sure.
 A: Either.
It's context dependent. Chemists generally mean the whole atoms, nuclear physicists usually mean the nucleus, and people not in those categories could mean either. And there are exception to all those rules or thumb.
And the distinctions is important when people start throwing masses around because the mass of an electron is almost on the same order as typical per-nucleon mass deficits.
A: The notation is that of one specific isotope (isotopes are nuclides with the same number of protons) of the chemical element Pu. 94 is the number of its protons, which is also the total charge, 240 is the total number of nucleons (protons and neutrons). In a neutral Pu atom there will always be 94 electrons to offset the charge of the protons in the nucleus. All neutral Pu atoms therefor have the same number of protons and electrons, but the number of neutrons differs from isotope to isotope. When chemists are talking about an element, they usually mean a chemical mixture of different isotopes of that element, mostly the mixture that occurs naturally. 
A: The entire atom is referred to by Pu.
