What is the difference between an enthalpy driven reaction and entropy driven reaction?

Enthalpy is regarding the amount of heat that is given off or taken in during the process of a reaction, while entropy is about the disorderliness of a reaction. 
Both are related in the equation ∆G=∆H-T∆S, where ∆G is the Gibbs free energy. So we can say that a reaction is both enthalpy and entropy driven. It's like, both of them are interlinked with each other. 

There is one s orbital, and there are three p orbitals, five d orbitals, and seven f orbitals. thus, the answer is b. do not confuse the number of orbitals in a subshell with the number of electrons the subshell can hold. each orbital can hold two electrons, so the capacity of an nf subshell is 14 electrons.