Why do I have to learn about electron shells.

This knowledge may not help you become good at your job in the future, but it is critical knowledge for everyone to have. electrons exist in certain energy levels around the atom. When an atom is hit by a ray of light, the energy from the light will be absorbed by the electron and the electron will move to a higher energy level (we call this an excited electron). However the amount of energy a given electron needs to jump to a higher energy level is discrete and it is a well known amount for each electron in each level. This means, electrons of different atoms can only absorb a certain wavelength of light. As time goes by, the electron loses that energy by emitting light of the same wavelength. This ray of light emitted has different colours depending on the type of atom. Now imagine this process of gaining and loosing electrons to happen infinite times every second. As a result of this process we are able to see the world around us and identify different colours of different materials.