Orbitals for ℓ > 3 continue alphabetically, omitting j (g, h, i, k, ...) because some languages do not distinguish between the letters "i" and "j". Atomic orbitals are the basic building blocks of the ...

That means all of the elements in the third period — sodium, magnesium, aluminum, silicon, phosphorus, sulfur, chlorine and argon — have three atomic orbitals where their electrons reside.