Which orbital is known for having the lowest energy?

The s orbital is known for having the lowest energy among the different types of atomic orbitals. This is primarily due to its spherical shape and the fact that it can hold a maximum of two electrons. In an atom, the energy levels of electrons increase with the complexity of the orbital shape; the s orbital is the simplest, featuring a single sublevel. Because of its lower energy level, the electrons that occupy s orbitals are typically found closer to the nucleus, where the attractive force from the protons is stronger.

In contrast, p, d, and f orbitals have more complex shapes and higher energy levels. The p orbitals, for instance, have a dumbbell shape and can hold up to six electrons, while the d orbitals can accommodate ten electrons, and the f orbitals can hold up to fourteen electrons. These additional complexities require more energy for the electrons to occupy these orbitals, making them higher in energy compared to the s orbital. Consequently, the s orbital naturally fills first in the arrangement of electrons in an atom, reinforcing its position as the orbital with the lowest energy.