and they are #n,l,m_l,m_s#. Each specifies a different meaning and its function.

#n# is the principal quantum number and states the energy level of an electron. You can think of it as the electron shell number. It can only be a whole number greater than 0, i.e. #n>0,AAninZZ#.

#l# is the angular momentum number and specifies the subshell #(s,p,d,f,...)# of an atom. It therefore determines the shape of the orbital. The conditions are such that #l=0,1,2,3,4,...,(n-1)#.

#m_l# is the magnetic angular momentum number, and determines the number of orbitals in the subshell. The conditions are such that #m_l=-l,(-l+1),(-l+2),...,-2,-1,0,1,2,...,(l-2),(l-1),l#.

#m_s# is the electron spin number and states the direction spin of an electron. It only has two values and does not depend on another quantum number. Conditions are that #m_s=+-1/2#. Positive #1/2# means an #uarr# spin while negative #1/2# designates a #darr# spin.