Final answer:
The Lewis structure for hydrogen cyanide (HCN) should show a total of 10 valence electrons, which is sum of the individual valence electrons from each hydrogen, carbon, and nitrogen atom. The correct option is c.
Step-by-step explanation:
The question asks how many electrons must be shown in the Lewis structure of hydrogen cyanide (HCN). To answer this, we must first determine the total number of valence electrons in the HCN molecule.
Each hydrogen atom has one valence electron, each carbon atom has four, and each nitrogen atom has five (since carbon and nitrogen are in the 14th and 15th groups of the periodic table, respectively). The sum of these gives us: (1×1) + (1×4) + (1×5) = 1 + 4 + 5 = 10 valence electrons.
Therefore, the correct answer would be option c. 10, which represents the total number of valence electrons to be used in the Lewis structure for hydrogen cyanide.