Question

Why is ${\mathrm{B}}_2$ paramagnetic while ${\mathrm{C}}_2$ is diamagnetic?

Answer 1

Paramagnetic and diamagnetic

• Materials having unpaired electrons are paramagnetic and attracted to a magnetic field.
• Examples of paramagnetic: aluminum, gold, and copper.
• Materials containing paired electrons are diamagnetic and repel a magnetic field.
• Examples of diamagnetic: copper, zinc, silver.

${\mathbf{B}}_{\mathbf{2}}$ paramagnetic while ${\mathbf{C}}_{\mathbf{2}}$ is diamagnetic

• The molecular orbital electronic configuration of ${\mathrm{B}}_2$:

${\left(\sigma 1s\right)}^2\left(\sigma *1s^{\mathit{2}}\right){\left(\sigma 2s\right)}^2{\left(\sigma *2s\right)}^2{\left(\pi \mathit{2}{p}_x\right)}^1{\left(\pi 2p_y\right)}^1$

• ${\mathrm{B}}_2$ has two unpaired electrons.
• Therefore, ${\mathrm{B}}_2$ is paramagnetic.
• The molecular orbital electronic configuration of ${\mathrm{C}}_2$:

${\left(\sigma 1s\right)}^2\left(\sigma *1s^{\mathit{2}}\right){\left(\sigma 2s\right)}^2{\left(\sigma *2s\right)}^2{\left(\pi \mathit{2}{p}_x\right)}^2{\left(\pi 2p_y\right)}^2$

• ${\mathrm{C}}_2$ has no unpaired electron.
• Therefore, ${\mathrm{C}}_2$ is diamagnetic.