Question

Why are the spheres representing nitrogen and oxygen different colors?

Answer 1

To be able to tell the atoms apart in a model of the compounds, or elements.

Explanation:

Oxygen is usually represented as a red sphere with two holes.(because Oxygen usually forms 2 bonds) This represents Oxygen's ability to aid in combustions ( fires)

Nitrogen is usually represented as a blue sphere. atmospheric nitrogen is very stable forming a diatomic molecule `N_2` with three bonds between the two atoms. ( the blue sphere has five holes because nitrogen can form up to five bonds though usually only 3 )

Molecular modes use different colors to aid in understanding the atomic structure of the model. Red for Oxygen, Blue for Nitrogen. Black for Carbon, and White for Hydrogen.