Question

Non-directional orbital is:
A. $3{\text{s}}$
B. $4{\text{f}}$
C. $4{\text{d}}$
D. ${\text{4p}}$

Answer 1

Hint: Orbital is a mathematical expression also called a wave function which describes the characteristic of no more than two electrons in the surrounding of an atomic nucleus or of a system of nuclei as in a molecule.

Complete answer:
In chemistry and quantum mechanics an orbital is a mathematical function which explains the wave-like behavior of an electron, electron pair. It may be called an atomic orbital or electron orbital and the purpose of this mathematical function is to map the probability of the location of an electron in a region around an atomic nucleus.
An orbital can contain two electrons with paired spins which is associated with a specific region of an atom, the s orbital, p orbital, d orbital, and f orbital which refer to the orbital that have an angular momentum quantum number 'l' is equal to zero, one, two and three, after s, p, d, and f, orbital names beyond 'l' equals to three are alphabetical (g, h, i, k...).
s orbitals are non-directional because they have spherical symmetry which means that the probability of finding an electron at a particular distance from the nucleus is same in all directions as compared with a p orbital which has somewhat a dumbbell like shape.
So distance from the nucleus within these orbitals is the same in spherical shaped orbital and therefore they are non-directional.

Hence the correct option is A i.e. $3{\text{s}}$.

Note: The angular momentum quantum number also known as azimuthal quantum number denoted by 'l' for an atomic orbital explains its orbital angular momentum and also the shape of the orbital that an electron occupies.