One neutral atom of carbon has four valence electrons. An easy way to tell how many valence electrons an element has is to look at the periodic table and find the element's main group number. Carbon is in group 4, which means it has four valence electrons.
Valence electrons are the electrons found in an atom's outer electron shell. A neutral carbon atom has a total of six electrons, but not all six electrons are located in the same energy level. Two of them are located in the first shell, while the remaining four are located in the second shell. The four electrons in the second shell are the valence electrons.
Valence electrons are important because they help determine if an element is able to participate in a chemical reaction.