To determine the number of valence electrons in a molecule, you need to consider the valence electrons of each individual atom in the molecule and then account for any additional electrons due to the presence of a charge or the formation of bonds.
In the case of pentacarbon dioxide (C5O2), you have five carbon atoms (C) and two oxygen atoms (O).
Carbon (C) is in Group 14, so it has 4 valence electrons. Since there are five carbon atoms, the total number of valence electrons contributed by carbon is 5 * 4 = 20.
Oxygen (O) is in Group 16, so it has 6 valence electrons. Since there are two oxygen atoms, the total number of valence electrons contributed by oxygen is 2 * 6 = 12.
To find the total number of valence electrons in C5O2, you sum up the contributions from carbon and oxygen: 20 (from carbon) + 12 (from oxygen) = 32.
Therefore, pentacarbon dioxide (C5O2) has 32 valence electrons.