## Chemistry and Chemical Reactivity (9th Edition)

Assuming $0\leq L\leq N$ There are $N+1$ subshells per shell and 3 orbitals per subshell (-1 ,0 and 1), so for the first three: $(2+3+4)×3=27$ If on the other hand $L=N$ There is 1 subshell per shell and 3 orbitals per subshell, so for the first three: $3×3=9$