Question #28c50
1 Answer
Answer:
To designate a specific orbital within a subshell, you need
Explanation:
The principle quantum number,
 For example, the
#3d# subshell is in the#n=3# shell, the#2s# subshell is in the#n = 2# shell, etc.
The angular momentum quantum number,
 For example, the
#n=3# shell has subshells of#l=0,1,2# , which means the#n=3# shell contains#s# ,#p# , and#d# subshells (each containing their respective orbitals). The#n=2# shell has#l=0,1# , so it contains only#s# and#p# subshells.
The magnetic quantum number,

So, for a
#2p# orbital with#n=2# and#l=1# , we can have#m_1=1,0,1# . This tells us that the#p# orbital has#3# possible orientations in space. 
If you've learned anything about group theory and symmetry in chemistry, for example, you might remember having to deal with various orientations of orbitals. For the
#p# orbitals, those are#p_(x)# ,#p_(y)# , and#p_(z)# . So, we would say that the#2p# subshell contains three#2p# orbitals (shown below).
Therefore, to describe any specific orbital within a subshell, where we care about the specific orientation of the orbital, we would need three quantum numbers, as described above.
If we had all four quantum numbers, we could then begin to describe the electrons "within" the orbitals. The fourth quantum number is the electron spin quantum number,
 Remember that there are only two electrons to every orbital, and that they should have opposite spins (again, this is because electrons are fermions
#># think Pauli exclusion principle). This tells us that there are two electrons per orbital, or per#m_l# value: one with an#m_s# value of#+1/2# and one with an#m_s# value of#1/2# .
In summary,