Hello; I couldn't find the answer to this anywhere, so I thought that I might ask here instead. What are the electron shell capacities for any given element? I think that any elements that are arranged in GROUPS have electron capacities that follow the pattern; 2,8,8,18,18,32,32... is this correct? And, as for elements that are not arranged in groups, i.e. actinides, lanthanides, and transition metals, will it follow the pattern of (3n2 - 2)? i.e. 2,8,18,32,50,72,98,128... ? For example, the formula of gold bromide would be AuBr, because the charge of a gold ion is Au+ (because according to my pattern it has 1 electron in its outer shell) and because the charge of a bromine ion is Br-. So is this why the formula should be AuBr (as an example)? EDIT: I looked up gold bromide on Wikipedia, which lists gold bromide as having the formula AuBr3. Why?