The possibility of bonds formation by a carbon atom is as follows:

1. a) i. Four single covalent bonds, with atoms of same element like hydrogen, Chlorine
   
   Eg: CH₄ , CCl₄ or H | H – C – H | H , C l | Cl – C – Cl | Cl
   
   ii. Four single covalent bonds with atoms of different elements ;
   
   Eg: H | H – C – Cl | Br
   
   b) Carbon atoms may form one double bond and two single bonds HH
   
   Eg: CC HH HO ; H CC HH
   
   c) Carbon atom may form one single bond and a triple bond
   
   Eg: H–C C–H or CH₃ –C N or carbon atoms may also    form two double bonds as in CH₂ = C = CH₂

• How do carbon atoms form bonds in so many different ways as mentioned above?


• Explain the four unpaired electrons in carbon atom through excited state

As per valence bond theory (see chapter-8, chemical bonding), the four unpaired electrons in a carbon atom are shown by suggesting excited state to carbon atom.

Electronic configuration of carbon ( ground state):

1s² 2s² (or) 1s² 2s² 2p_x ¹2p_y ¹2p_z⁰

Electronic cknfiguration of carbon (excited state):

1s² 2s¹ 2p_x ¹2p_y ¹2p_z¹