Let’s take a look at sodium (Na) and chlorine (Cl). Draw what I am describing, and you will see it better. A sodium atom has how many protons? A sodium atom has how many electrons? How many electrons will go in the first shell? How many in the second shell? How many in the third? Now draw this out on the diagram in Figure 2.1, and take a look at it, in particular the third (valence) shell. We know that Na requires eight electrons in its valence shell to become stable. But how many does it have? So, to fill this shell, will it be easier for sodium to steal seven more electrons from another atom, or will it be easier for sodium to give up that one electron and get rid of that third shell? Sodium is simply going to give away that last electron. This means that it will lose an electron (negative charge) but will keep the same number of protons (positive charges). What will the sodium ion’s overall charge be now? _

I have attached a photo below of the answer, it is very detailed. If you want a typed up version, here you go.
A sodium atom has 11 protons and 11 electrons. 2 electrons will go in the first shell, 8 will go in the second shell, and 1 will go in the third shell. Because sodium has 11 electrons, it has one extra in the third shell, making it unstable. It will get rid of that single electron and it’s third shell so it can become stable. After this, there will be more protons than electrons, giving it a positive charge. Hope this helps you and again, the photo holds a lot more detail with some notes and a drawing that can help you. Good luck and stay safe!