# Why do the d suborbitals start at 3d instead of 4d?

Why do the suborbitals for d start at 3 instead of four? It is in the fourth row on the periodic table and all other suborbitals start according to the row on which they are located except for d. Why is that?

• – Tyberius Dec 12 '17 at 16:37
• Actually $d$ orbitals are not exceptional. $4f$ orbitals come in row 6. – Oscar Lanzi Dec 12 '17 at 18:58

If you do the math you'll see that in the 3rd period there's the main quantum number $n=3$ which allows the secondary quantum number $l$ to take the values 0, 1 or 2. As $l$ determines the kind of the orbital you get a $s$, $p$ or $d$ orbital.