BBQ said she had been a girl and a friend
The reaction is exothermic, the energy in the bonds has been released to the surroundings (causing the potential energy to go down). The increase in energy in the surrounding heats them up hence exothermic.
None. To bind with an hydrogem atom, the carbon needs to ''share'' one of it's valence electron's with the hydrogen's valence electron. Therefore, forming 4 bounds means the carbon atom will share it's 4 valence electrons and there will be no lone electrons.