The Lewis structure of HCN (H bonded to C) shows that __________ has __________ nonbonding electron pairs.

The Lewis structure of HCN (H bonded to C) shows that Nitrogen (N) has one nonbonding electron pair.

Here's the step by step process:

1. Identify the total number of valence electrons. Hydrogen has 1, Carbon has 4, and Nitrogen has 5. So, total valence electrons are 10.

2. Draw a skeleton structure of the molecule. H is bonded to C, and C is bonded to N.

3. Connect the atoms with single bonds. This uses up 2 electrons for each bond, so 4 electrons are used.

4. Distribute the remaining electrons as lone pairs, starting with the outer atoms first. Nitrogen gets 6 electrons (3 pairs), but one of these pairs is involved in bonding with Carbon, leaving it with 2 nonbonding pairs.

5. Check the structure to see if each atom (except Hydrogen) has an octet (8 electrons). In this case, Carbon only has 6 electrons, so we need to move one of Nitrogen's lone pairs to form a triple bond with Carbon.

6. Now, Nitrogen has 1 nonbonding electron pair, Carbon has 0, and Hydrogen doesn't have any nonbonding pairs because it can only form 1 bond.