Which combinations of n and l represent real orbitals, and which do not exist a) 2s b) 3p c) 5s d) 1d

Answer : The combinations of n and l don not exist is, (d) 1d

Explanation :

Principle Quantum Numbers : It describes the size of the orbital and the energy level. It is represented by n. Where, n = 1,2,3,4

Azimuthal Quantum Number : It describes the shape of the orbital. It is represented as 'l'. The value of l ranges from 0 to (n-1). For l = 0,1,2,3... the orbitals are s, p, d, f...

(a) For 2s :  

n=2 and l can have value 0 to (n-1) i.e. 0 and 1 only. For s, l=0 which is possible.

(b) For 3p :  

n=3 and l can have value 0 to (n-1) i.e. 0, 1 and 2 only. For p, l=1 which is possible.

(c) For 5s :  

n=1 and l can have value 0 to (n-1) i.e. 0, 1, 2, 3 and 4 only. For s, l=0 which is possible.

(d) For 1d :  

n=1 and l can have value 0 to (n-1) i.e. 0 only. For d, l=2 which is not possible.

Hence, the combinations of n and l don not exist is, (d) 1d

definition

                    entropy is a measure of the randomness or the extent of disorder of a chemical process.

                      enthalpy is a measure of the heat change of a reaction occurring at a constant pressure.

measurement units:

                        entropy is measured in joule per kelvin (jk⁻¹)   whereas enthalpy is measured in joule per mole (jmol⁻¹)

requirements:

                            entropy has no requirements or limits, and its change is measured by the division between the heat change of the chemical process and the temperature.

                              in contrast, enthalpy can only be related to the heat change of the reaction under standard conditions.

you need to have a picture of the atom that way we can answer it