# Domanda n. 95d67

#### Risposta:

Those letters are used just by historical reasons.

#### Spiegazione:

The first time that atomic orbitals were observed, it was done by spectroscopists, which observed them as lines on the atomic spectra.

Here, there are some examples of atomic spectra for several elementi:

Fonte: www.wonderwhizkids.com

Each of the lines correspond to a transition to (or from) some of the blocks. They were called in that way according to how they were observed on alkali spectra:

• s for sharp lines.
• p for principal lines.
• d for diffuse lines.
• f for fundamental lines.

Dopo f, they just follow alphabetical order, skipping j (which is reserved to represent angular momentum):

g, h, i, k, l, m, n...