![]() You see how that works? What do you think is true about the alkaline earth metals, that's group two. The potassium cation is isoelectronic with the argon. So sodium becomes isoelectronic with neon when it's sodium one plus. And they become isoelectronic with noble gases by losing one electron. It's a very, it's a very low ionization energy electron if you will. In fact, everything in group one, all of the alkaline metals, prefer to lose one electron, they lose that electron quite easily. Which of the noble gases over here, is closest to the number of electrons to lithium? Well helium is, right? Helium has two, so lithium, can lose one of the three electrons, and become isoelectronic with helium. Okay, so that's what I'm focusing on right now. But, it does include also group 13 through 18. ![]() Lanthanide and actinide are inter transition metals. So we're not going to talk about those right now. So, for the main group elements, that includes group one and two, remember? Does not include the transition metal. But for now, let's just say, it wants to have the same number of electrons as a noble gas. So what does this word isoelectronic mean? That means it has the same electron configuration, and we haven't talked about electron configurations. It's the main group elements that like to be isoelectronic with the noble gasses. Now, let's look at the main group elements. But, really it sometimes act like a metal and sometimes like a nonmetal. You know, I like to put it kind of in the middle. So you see hydrogen there is right above lithium. So the first thing I'm going to do to make the periodic table more the way I personally like it is move hydrogen. Sometimes it does loose an electron, like in alkaline metals, but other times it doesn't. I don't actually think that's the best place for hydrogen. This periodic table has drawn hydrogen above the alkaline metals. What do I mean by an atom becoming isoelectronic with a noble gas? Well let's take a look at the periodic table and see. Another driving force that you may have heard about is that atoms of the main group elements want to become isoelectronic with the noble gases. So the electrons can go to lower energy by leaving metals and joining nonmetals. Are that, the system wants to lower its energy. The driving force, once again, for these processes. They tend to gain electrons, often by taking those electrons away from metals, and the nonmetals tend to form anions. Which means they have large electronegativity. Nonmetals on the other hand, have relatively low energy open orbitals. They tend to lose electrons and become cations because of this. One of the things you might remember is that the metals have relatively small ionization energy. Look at a periodic table now, to remind yourself of a couple of periodic trends that have been discussed in this course. Finally, we'll wrap up by talking about some of the common polyatomic ions. In this lecture I'll review the driving forces for ion formation, and show how this was translated into a set of rules for assigning oxidation states to atoms in all kinds of compounds.
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