how many valence electrons does carbon have?

Carbon has 4 valence electrons. This is because its atomic number is 6, with an electron configuration of 1s22s22p21s^22s^22p^21s22s22p2. The electrons in the outermost shell, which is the second shell here, are the valence electrons, totaling four (two in 2s and two in 2p orbitals).