What is the total number of outer (valence) electrons in carbon dioxide, co2? answer?

Carbon dioxide has a total of 16 valence electrons.

1. To determine the number of valence electrons of carbon dioxide (CO2), first determine the number of valence electrons of each of the elements in the molecule. 

a. We have 1 carbon (C) molecule, and 2 oxygen (O) molecules. 

b. The carbon molecule has 4 valence electrons and each oxygen molecule has 6 oxygen molecules. 

2. Add up the valence electrons of each of the elements

   4            +          (2 x 6)      = 16
(from C)           (2 oxygen molecules, with 6 valence electrons each)

Thus, CO2 has a total of 16 valence electrons. 

The number of valence electrons can be more clearly seen from the Lewis structure of the CO2 in the figure below (Source: http://chemistry.tutorvista.com/inorganic-chemistry/bonding-electrons.html). The the dots surrounding the letters represent the valence electrons.