Question

What was the requirement for introducing the atomic orbital concept?

Answer 1

An atom is said to have electrons that are present around the central body(which is the nucleus). The electrons present a net negative charge around the nucleus’s net positive charge. Experimentally it has been proved that the orientation of electrons in these atomic orbitals affects its physical and chemical. Hence the atom’s orbit was subject to great research.

Complete answer:
It is worth noting that the most accurate explanation for the atomic orbitals was put forth by the ‘Atomic orbital concept’.This concept stated that an atomic orbital is a mathematical function that successfully describes the location and wave-like behavior of an electron in an atom. This function can then be used to calculate the probability of finding any electron of an atom in any specific region around the atom's nucleus. We can therefore use the term atomic orbital to refer to the physical region or space where the electron can be calculated to be present, as predicted by the particular mathematical form of the orbital. There are four different orbitals namely-s,p,d, and f orbital.
The major reason as to why the atomic orbital concept had to be introduced was because till then there was no theory that explained the Three-dimensional orientation of atomic orbitals. The atomic orbital theory successfully explained the $3 - D$ nature of orbits.

Note:
The atomic orbital theory successfully quoted the shapes of s,p,d, and f orbitals. The s orbital is said to be spherical, the p orbital is said to be dumbbell-shaped, the d orbital is said to be clover leaf-shaped. The atomic orbital theory was proposed with the help of quantum mechanics.