electrons and atoms behave as giraffes wait no waves weird yes easy to understand not really important definitely the whole periodic table all of the amazing properties of the elements come down to the properties and behaviors of these electron waves let's recap what we know about electron waves one the more loops that they have the higher an energy and larger they are that's n the principal quantum number two their shape depends on the number of nodal planes in the wave that's l the azimuthal quantum number to understand the properties of single electron species we can pretty much stop here but that would be no fun after all the interesting elements all have more than one electron so what other properties do we need to know one thing we have already intuited is that electrons will be the lowest possible energy wave unless you do something to them we call the lowest energy state of an atom its ground state what is the ground state of a hydrogen atom hydrogen's electron is a 1s electron unless it is excited this is another principle of electrons so let's add to our list with number three electrons will always be in the lowest possible energy state that they can be this is the aufbau principle there is one more principle that's a little harder to intuit the polyexclusion principle it says that you can't have two electrons with identical quantum numbers but you can have two 1s electrons in an atom and even more 2p electrons right now this might be a little confusing for this to make sense we need to talk about a few more quantum numbers that'll be the topic of the next few videos