Question

What is the electronic configuration of a hydrogen atom?

Answer 1

The hydrogen atom is the first element of the modern periodic table. Elements in the periodic table are arranged in an increasing order of their atomic numbers which means that hydrogen is the element with the lowest atomic number.

Complete answer:
The structure of an atom is such that it contains a dense positively charged nucleus that is known to contain the entire mass of an atom concentrated in a small spherical volume.
The electrons are negatively charged and the mass contributed by them is almost negligible in comparison to other subatomic particles like protons and neutrons.
The electrons are not accumulated in a small volume like protons but are placed in fixed energy levels where they revolve around the nucleus. The electrons in shells are filled one by one and no higher shell is filled before the shells below it are already filled with electrons. Thus each shell have a fixed number of electrons that it can accommodate and this sums up the Aufbau principle of filling up electrons.
Hydrogen being the first element of the periodic table, it has only one proton in its nucleus and one electron in its first shell.
The first orbital of the lowest energy level is the $1s$ orbital. Thus hydrogen contains a single electron in the $1s$ level.
Hence the electronic configuration of hydrogen atoms is $1{s^1}$ .

Note:
The notation $1{s^1}$ gives us the information that the value of the principal quantum number i.e. the energy level is one, the orbital is $s - orbital$ which means that the azimuthal quantum number value is zero and a single electron is present. The values of magnetic quantum number and spin quantum number cannot be decided by simply looking at the electronic configuration.