In oxygen and carbon molecule the bonding is
$\mathrm{O}_2: 2 \sigma, 0 \pi ; \mathrm{C}_2: 0 \sigma, 2 \pi$
$\mathrm{O}_2: 1 \sigma, 1 \pi ; \mathrm{C}_2: 0 \sigma, 2 \pi$
$\mathrm{O}_2: 0 \sigma, 2 \pi ; \mathrm{C}_2: 2 \sigma, 0 \pi$
$\mathrm{O}_2: 1 \sigma, 1 \pi ; \mathrm{C}_2: 1 \sigma, 1 \pi$
