Paramagnetic vs diamagnetic behavior
Paramagnetic vs diamagnetic classification rests on electron spin pairing. Unpaired electrons create a net magnetic moment that couples to an external magnetic field, producing attraction into the field region. Fully paired electrons produce no permanent net magnetic moment, and the induced response is weakly opposed to the applied field, producing weak repulsion.
Paramagnetic vs diamagnetic: paramagnetic substances contain one or more unpaired electrons and are attracted into a magnetic field; diamagnetic substances have all electrons paired and are weakly repelled.
Electron pairing as the deciding criterion
Electron configuration provides the decisive test for atoms and ions: at least one singly occupied orbital implies paramagnetism, while complete pairing in all occupied orbitals implies diamagnetism. For molecules, the same logic applies to molecular orbitals: singly occupied molecular orbitals imply paramagnetism, while fully paired occupancy implies diamagnetism.
- Unpaired electrons present → paramagnetic response (attraction).
- All electrons paired → diamagnetic response (weak repulsion).
Quantitative link to unpaired electrons
In many introductory general chemistry contexts (especially for transition-metal ions and radicals), the magnitude of the magnetic moment correlates with the number of unpaired electrons \(n\) through the spin-only estimate \( \mu \approx \sqrt{n(n+2)}\,\mu_B \), where \(\mu_B\) is the Bohr magneton. The qualitative classification in paramagnetic vs diamagnetic comparisons depends only on whether \(n = 0\) or \(n \ge 1\).
Comparison table
| Property | Paramagnetic | Diamagnetic |
|---|---|---|
| Electron occupancy | At least one unpaired electron (singly occupied orbital) | All electrons paired (no singly occupied orbitals) |
| Net magnetic moment (no external field) | Nonzero at the microscopic level (from unpaired spins) | Zero (paired spins cancel) |
| Response in an external field | Attracted into higher-field regions | Weakly repelled from higher-field regions |
| Typical chemistry examples | O2, many transition-metal ions with unpaired d electrons, radicals | N2, noble gases, closed-shell ions (e.g., Na+, Cl−) |
| Magnetic susceptibility (qualitative) | Positive and relatively larger | Negative and small in magnitude |
Visualization: molecular orbital filling and magnetic behavior
Worked classifications that commonly appear in general chemistry
Closed-shell atoms and ions (filled subshells) fall on the diamagnetic side of paramagnetic vs diamagnetic comparisons. Species with partially filled subshells or singly occupied molecular orbitals fall on the paramagnetic side.
| Species | Electron pairing highlight | Classification |
|---|---|---|
| He | \(1s^2\), all paired | Diamagnetic |
| N (atom) | \(1s^2 2s^2 2p^3\), three unpaired in \(2p\) | Paramagnetic |
| N2 | Valence MOs fully paired | Diamagnetic |
| O2 | Two unpaired electrons in π*2p | Paramagnetic |
| Na+ | \(1s^2 2s^2 2p^6\), closed shell | Diamagnetic |
| Fe3+ (high-spin, common ionic picture) | Unpaired \(d\) electrons present | Paramagnetic |
Common confusions
The words “magnetic” and “attracted” often evoke ferromagnetism, which is a different phenomenon (domain alignment) and typically involves solids such as iron metal. Paramagnetic vs diamagnetic comparisons in general chemistry refer to weak, electron-based responses that depend on unpaired versus paired electrons, not on permanent magnetic domains.