Final answer:
The chemical formula for a compound formed from one nitrogen atom and three chlorine atoms is NCl3, as each chlorine forms a single covalent bond with the nitrogen atom.Answer is option (a).
Step-by-step explanation:
When three chlorine atoms covalently bond with a nitrogen atom, the resultant compound will be nitrogen trichloride, which has the chemical formula NCl3. This is because nitrogen (N), which is in group 15 of the periodic table, has 5 valence electrons and requires three additional electrons to complete its octet.
Chlorine (Cl), being in group 17, has 7 valence electrons and needs just one electron to complete its octet. Therefore, each chlorine atom forms a single covalent bond with nitrogen. The correct chemical formula reflects one nitrogen atom covalently bonded to three chlorine atoms, as each chlorine atom satisfies one of the three available bonding sites on the nitrogen atom.