Given, n= principal quantum number The principal quantum number is one of four quantum numbers assigned to each electron in an atom to describe that electron state. As n increases, the electron is also at a higher energy and is, therefore less tightly bound to the nucleus. l= azimuthal quantum number The azimuthal quantum number is a quantum number for an atomic orbital that determines, it orbital angular momentum and describes the shape of the orbital. Azimutal quantum number (l)=0,1,2,3,4 Shape of orbitals =s,p,d,f,g Energy of orbitals $s So, higher the value of n and l higher the energy of electron. Decreasing order of energy for the electrons, n=5 and "l=2>n=4 and l=3>n=5 and l=0>n=4 and l=1 i.e. A>C>B>D