Question

Why does potassium have $4$ energy levels?

Answer 1

We need to know that a quantum mechanical framework or molecule, that is bound, that is, restricted spatially, can just interpret certain discrete upsides of energy, called energy levels. This differentiation with traditional particles, which can have any measure of energy. The term is normally utilized for the energy levels of the electrons in atoms, particles, or atoms.

Complete answer:
In science and nuclear physical science, an electron shell, or head energy level, might be considered as the circle of at least one electron around an atom's core. The nearest shell to the core is known as the first shell (called K shell), trailed by the second shell (or L shell), then, at that point the third shell or M shell, etc farther and farther from the core. The shells compare with the central quantum numbers ( $n = 1,2,3,4..$ ) or are marked sequentially with letters utilized in the X-beam documentation (K, L, M, N… ).
Each shell can contain just a fixed number of electrons. The main shell can hold up to two electrons, the subsequent shell can hold up to eight $\left( {2 + 6} \right)$ electrons, the third shell can hold up to $18$ $\left( {2 + 6 + 10} \right)$ , etc. The overall recipe is that the nth shell can on a fundamental level hold up to $2{n^2}$ electrons. Since electrons are electrically drawn to the core, a molecule's electrons will for the most part involve external shells just if the more internal shells have effectively been totally filled by different electrons. Notwithstanding, this is certifiably not an exacting necessity, particles may have two or even three inadequate external shells. For a clarification of why electrons exist in these shells see electron setup.
Potassium has four energy levels, because potassium has $19$ electrons and $19$ protons. This is on the grounds that two electrons possess the principal energy level, eight electrons involve the subsequent energy level, again eight electrons possess the third energy level, and the extra one electron involves the fourth energy level.

Note:
As we know that the electrons in the furthest energy level of a particle have an extraordinary importance. These electrons are called valence electrons, and they decide large numbers of the properties of a molecule. A particle is generally steady if its furthest energy level contains however many electrons as it can hold.