Explanation:

The semicarbazone molecule of acetone is formed by the reaction of acetone (CH3COCH3) with semicarbazide (NH2CONHNH2). In this reaction, one of the carbonyl groups in acetone reacts with the amino group of semicarbazide to form a semicarbazone.

The molecular formula of acetone is CH3COCH3, which means it contains three carbon atoms, six hydrogen atoms, and one oxygen atom. On the other hand, the molecular formula of semicarbazide is NH2CONHNH2, which means it contains one nitrogen atom, four hydrogen atoms, one carbon atom, and two oxygen atoms.

When acetone reacts with semicarbazide, the carbonyl group in acetone (-C=O) reacts with the amino group in semicarbazide (-NH2) to form a C=N double bond, resulting in the formation of a semicarbazone molecule.

Key Points:

- Acetone (CH3COCH3) reacts with semicarbazide (NH2CONHNH2) to form a semicarbazone.
- Acetone contains three carbon atoms, six hydrogen atoms, and one oxygen atom.
- Semicarbazide contains one nitrogen atom, four hydrogen atoms, one carbon atom, and two oxygen atoms.
- The carbonyl group in acetone (-C=O) reacts with the amino group in semicarbazide (-NH2) to form a C=N double bond.
- The resulting molecule, semicarbazone, contains three nitrogen atoms.

Conclusion:

Therefore, the correct answer is that there are three nitrogen atoms in a semicarbazone molecule of acetone.