The format AXZ is used when writing about specific isotopes. Here X is the chemical symbol for the element, Z is the atomic number, and A is the number of neutrons and protons combined (the mass number).
Image: http://www.radiation-scott.org/timeline/isotope_definition_LARGE.jpg
Ions are atoms that have lost or gained electrons so that they are no longer electrically neutral. Electrically neutral atoms have equal numbers of protons and electrons. Anions are ions with negative electrical charges due to gained electrons, while Cations are ions with positive electrical charges due to lost electrons.
When writing about ions, the format Xn(+/-) is used. Here X is the chemical symbol for the element, n is the number of electrons gained or lost, and either a + or - sign is used to denote the charge of the ion.
Image: http://www.blueeyedcurse.com/Images/ions.jpg
