The hydrogen atom has a relatively low ionization energy compared to many other atoms because of its unique electron configuration and the nature of its single electron.
Ionization energy is the energy required to remove an electron from an atom, resulting in the formation of a positive ion. In the case of hydrogen, it consists of only one electron orbiting its nucleus, and this electron is located in the first energy level (1s orbital). The electron experiences a relatively weak attractive force from the positively charged nucleus because hydrogen has a single proton in its nucleus. As a result, the electron is less tightly bound to the nucleus compared to electrons in atoms with more protons.
Additionally, the electron in the hydrogen atom experiences a lower level of electron-electron repulsion compared to electrons in multi-electron atoms. In atoms with multiple electrons, the electrons repel each other due to their negative charges, leading to a higher overall energy and stronger electron-electron interactions. This increased repulsion makes it more difficult to remove an electron, resulting in higher ionization energies.
In contrast, the hydrogen atom's single electron is not shielded by other electrons, and there is no significant electron-electron repulsion to overcome. These factors contribute to the relatively low ionization energy of hydrogen.
It's worth noting that while hydrogen has a lower ionization energy compared to many other elements, there are other factors such as atomic size, effective nuclear charge, and electron configuration that also influence ionization energies across the periodic table.