Before we move on, electrons are now called orbitals.

So every time you see the term orbital, just know that it means electron.

That's not really the case. There's a beautiful and elegant distinction between orbitals and electrons but it's quite long + takes effort to understand. Hence, it's easier for us to get by by just interpreting orbitals as electrons. (We are not here to appreciate chemistry, we are just here for 4.0 right?)

Electrons move in a circular shell around the nucleus

Energy of electron is quantized

electrons will be promoted to a higher energy state (higher shell) when energy is supplied.

Electrons at higher energy state is unstable and will tend to fall back to its ground state while releasing excess energy in the form of EM waves (light)

represents the size of the orbital

higher number, bigger size

higher number, higher energy

represents the sub-shell the electron is in.

l=0 indicates that the electron is in the first subshell (s subshell)

l=1 indicates that the electron is in the second subshell (p subshell)

l=2 indicates that the electron is in the third subshell (d subshell)

l=3 indicates that the electron is in the fourth subshell (f subshell)

represents the orientation of the orbital

higher the l, higher the possible orientations of the orbital

represents the direction the electron is spinning

+1/2 = clockwise (denoted by an arrow pointing upwards)

-1/2 = anticlockwise (denoted by an arrow pointing downwards)