What Is The Principal Quantum Number?

Description

Quantum numbers were developed to characterize electrons – its electron configuration, movement and position in an atom. Each electron has a unique set of quantum numbers. Of the four quantum numbers, our focus in this lesson is the principal quantum number.

!!!What is the Principal Quantum Number?

Let us imagine an apartment building with multiple floors – the more floors there are, the more people can reside in the building, and each person’s address is different, based on the room and floor they occupy.

Just like each person or family occupies different floors in the apartment building, for electrons, they occupy different principal electron shells. How do we know which principal electron shell these electrons occupy? The

If you occupy a higher floor, and if there is no elevator, you need to spend more energy going to where you need to be. In the same way, as __’’n’’__ increases, this means that the energy of the electron also increases.

!!!Visualizing the Principal Quantum Number

When there are more floors in an apartment building, that means more people can occupy the building and spread out more on the floors. If there are not as many floors, the people occupying the building are more concentrated in a smaller space. The same can be said about the principal quantum number and electron density.

The principal quantum number tells us not only the energy of an electron, but also gives us an idea about the electron density around the nucleus of an atom. In the illustration below, it shows on the left, ‘’when the principal quantum number is smaller, that the electron density is more concentrated closer to the atom, which means the electron cloud is smaller. On the right, the electron density is more spread out when the principal quantum number is larger, and the electron cloud is larger’’. Principal Quantum Number and Electron

This means that ‘’the energy needed to remove an electron, the __ionization energy__, is smaller due to the lower attraction between the nucleus and the electron’’

The space in between each floor of an apartment building is a space that people cannot occupy. Electrons also have a space that they cannot occupy, called a ‘’node’’. A __node__ is an area where there is zero probability of finding an electron. The principal quantum number also tells us about the number of ‘’nodes’’ in an