To determine the number of valence electrons in the molecule HCN (Hydrogen Cyanide), we first need to take a look at each atom in the molecule and how many valence electrons they contribute.
1. **Hydrogen (H)**: Hydrogen is in Group 1 of the periodic table and has 1 valence electron.
2. **Carbon (C)**: Carbon is in Group 14 and has 4 valence electrons.
3. **Nitrogen (N)**: Nitrogen is in Group 15 and has 5 valence electrons.
Now, we simply add the number of valence electrons contributed by each atom:
Total Valence Electrons = Valence Electrons of H + Valence Electrons of C + Valence Electrons of N
Total Valence Electrons = 1 (from H) + 4 (from C) + 5 (from N) = 10
Therefore, the molecule HCN has a total of 10 valence electrons.