The correct option is B 20
The atomic number of carbon =6
Electronic configuration of Carbon is: [He] 2s2 2p2
Number of valence electrons: 4
Similarly, the number of valence electrons in Hydrogen (H) and Chlorine (Cl) are 1 and 7 respectively.In CH3CH2Cl, we have 2 carbon atoms, 5 hydrogen atoms and one chlorine atom. Hence, total number of valence electrons in CH3CH2Cl=4×2+1×5+7=20