Organska kemija in biokemija EN 20/21

You can find a detailed explanation of the periodic table at the Britannica webpage.

Here you have a shorter version, with a quiz at the end to test your understanding, please consider taking it and let me know if there's something that need additional explanation.

On lumenlearning you can find an explanation of orbitals, if you are not familiar with this concept, I warmly recommend looking at the part about the Aufbau principle. You will also find exercises at the end to test your knowledge.

For those more visual, here you are a few videos:

on the periodic table

chemical bonds

and the orbitals