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Chemistry · Glossary

What is Paramagnetic and diamagnetic?

Also known as: paramagnetic · diamagnetic

Definition 14.11 University Chemistry — Year 2 · Chapter 14 — Molecular Orbitals of Diatomic Molecules

A substance is paramagnetic if its molecules have unpaired electrons: it is drawn into a magnetic field. It is diamagnetic if all its electrons are paired: it is weakly pushed out of the field.

Valence molecular orbital diagrams of N2 (left, with s–p mixing: _2p above π_2p) and O2 (right). Nitrogen: bond order (8 - 2)/2 = 3, all electrons paired. Oxygen: bond order (8 - 4)/2 = 2, with two unpaired electrons in the two π* orbitals (Hund’s rule): O2 is paramagnetic. The diagrams take x as the molecular axis, hence the labels 2 _x, 2π_y, 2π_z. Valence molecular orbital diagrams of N2 (left, with s–p mixing: _2p above π_2p) and O2 (right). Nitrogen: bond order (8 - 2)/2 = 3, all electrons paired. Oxygen: bond order (8 - 4)/2 = 2, with two unpaired electrons in the two π* orbitals (Hund’s rule): O2 is paramagnetic. The diagrams take x as the molecular axis, hence the labels 2 _x, 2π_y, 2π_z.
Valence molecular orbital diagrams of NX2\ce{N2} (left, with s–p mixing: σ2p\sigma_{2p} above π2p\pi_{2p}) and OX2\ce{O2} (right). Nitrogen: bond order (8−2)/2=3(8 - 2)/2 = 3, all electrons paired. Oxygen: bond order (8−4)/2=2(8 - 4)/2 = 2, with two unpaired electrons in the two π∗\pi^* orbitals (Hund’s rule): OX2\ce{O2} is paramagnetic. The diagrams take xx as the molecular axis, hence the labels 2σx2\sigma_x, 2πy2\pi_y, 2πz2\pi_z.
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