The spin quantum number is one of the quantum numbers that describes the intrinsic angular momentum or “spin” of an electron in an atom. It is denoted by the symbol “ms.” Here’s a concise definition of the spin quantum number:
- The spin quantum number, represented by “ms,” describes the intrinsic angular momentum or spin of an electron.
- The spin quantum number has only two possible values: +1/2 and −1/2.
- These values represent the two possible directions of an electron’s spin in a magnetic field—often referred to as “spin up” (+1/2) and “spin down” −1/2.
- The spin quantum number is fundamental to the Pauli Exclusion Principle, stating that no two electrons in an atom can have the same set of four quantum numbers, including ms.
Examples
| Element | Number of Electrons | Possible Spin Quantum Numbers (m_s) | Explanation |
|---|---|---|---|
| Hydrogen (H) | 1 | +1/2 or −1/2 | An electron in a hydrogen atom can have a spin of either +1/2 or −1/2. |
| Oxygen (O) | 8 | +1/2 or −1/2 | Each of the eight electrons in an oxygen atom can independently have a spin of +1/2 or −1/2. |
| Iron (Fe) | 26 | +1/2 or −1/2 | Each of the twenty-six electrons in an iron atom can independently have a spin of +1/2 or −1/2. |
