How many orbitals can exist at the third main energy level?
There are 9 orbitals in 3rd energy level.
1st shell contains only s subshell, 2nd shell has s and p subshells while 3rd has s,p and d subshells.
s subshell has only 1 orbital, p subshell contains 3 orbitals and d subshell has 5 orbitals.
As 3rd shell has s.p and d subshells so it contains total 9 orbitals.