Draw a Lewis structure for nitrogen trichloride, `NCl_3`.

Explanation

Step 1: Calculate the number of valence electrons. The N atom has five and each Cl atom has seven, giving `5+(3xx7)=26` valence electrons.
Step 2: Determine the skeleton structure. Since Cl forms only one bond, unless it is bonded to O or F, and nitrogen tends to form three bonds, the skeleton structure must be
`Cl-underset(Cl)underset(|)N-Cl`
Note that the central N atom is less electronegative than Cl.
Step 3: The number of electrons used to form the three bonds in the skeleton structure is 6, leaving `(26-6=)20` electrons to complete the octets in the molecule.
Step 4: The number of electrons needed to complete all the octets is` [2 (for the N atom)+(3 x 6) (for the Cl atoms)=]20`.
Step 5: Since the number of electrons needed to complete all the octets (step 4) is the same as the number of available electrons (step 3), the Lewis structure is finished by completing the octets, writing the nonbonding valence electrons as pairs of dots:
`:overset(..)underset(..)Cl-underset( :underset(..)C: )underset|overset(..)N-underset(..)overset(..)Cl:`
Step 6: As final step, check to be sure that the Lewis structure has the correct number of valence electrons. The structure we have written for `NCl_3` has 26 electrons (6 bondings and 20 nonbonding), which is the number of valence electrons.