# Quantum Numbers - Revised¶

Each electron is described by four quantum numbers

## $$n$$ −1, 2, 3, 4, 5¶

• Energy level - This is effectively the period number
• The first number in the orbital descriptor
• $$\textbf{3}d^5$$

## $$l$$ −1(s), 2(s, p), 3(s, p, d), 4(s, p, d, f)¶

• Angular momentum/subshell - describes the shape of the orbital
• The letter in the orbital descriptor
• $$3\textbf{d}^5$$

## $$m_l$$¶

• The shape of the orbital
• The dimensionality of the orbital descriptor
• $$3d_{\textbf{xy}}^2$$

## $$m_s$$¶

• Electron spin
• Can be +½ or −½