Atomic Structure~

proton: has a relative mass of 1 and electric charge of +1; located in the nucleus.
neutron: has a relative mass of 1 and no electric charge; located in the nucleus.
electron: has a relative mass of almost 0, has a electric charge of -1; located in the cloud surrounding the nucleus.


Atomic number=the proton number


Atoms have no overall electric charge. Therefore, # of p+ = # of e-
anion: when e- is added to an atom
cation: when e- is removed from a atom.


Mass number= # of proton + # of neutron. (therefore, # of neutron = mass # - # of proton)
Atomic mass= the average mass of a element's isotopes


Isotope: have same atomic number but different atomic mass (in another word, different # of neutron)