(L)/angular momentum quantum number = is an energy sublevel within an shell in which the electrons all have the same energy
2. distinguishs shapes of orbitals
3. identified by letters s,p,d,f,g, etc...
4. the number of subshells w/in a shell is the same as the shell number (ex. shell 1=1 sub, shell 2=2 sub)
5. subshell differ in size & energy
ex. apartments on one floor of apartment building