The arrangement of electrons in an atom is governed by the principles of quantum mechanics. In the case of a hydrogen atom, which has only one electron, the electron's distribution into different orbits follows the Pauli exclusion principle and the principle of maximum multiplicity.
The Pauli exclusion principle states that no two electrons in an atom can have the same set of quantum numbers. Quantum numbers describe various properties of electrons, such as their energy, angular momentum, and magnetic orientation. This principle ensures that each electron within an atom is uniquely identified.
In the hydrogen atom, the energy levels or orbits available to the electron are labeled with quantum numbers. The first energy level is called the 1s orbital, followed by the 2s, 2p, 3s, 3p, and so on. According to the principle of maximum multiplicity, which is a consequence of the Pauli exclusion principle, each orbital can accommodate a maximum of two electrons with opposite spins.
When the hydrogen atom has only one electron, it occupies the lowest energy level, which is the 1s orbital. This means that the first electron goes into the 1s orbital with a specific set of quantum numbers. The quantum numbers of this electron describe its unique characteristics, such as its energy, angular momentum, and magnetic orientation.
Since the 1s orbital can hold a maximum of two electrons, and there is only one electron in the hydrogen atom, it fills the 1s orbital completely. As a result, the hydrogen atom contains only one electron in its lowest energy level, satisfying the Pauli exclusion principle and the principle of maximum multiplicity.
It's important to note that the distribution of electrons in atoms becomes more complex as the atomic number increases, leading to the filling of multiple energy levels and the formation of electron configurations. However, for the simplest case of hydrogen, with just one electron, only the 1s orbital is occupied.