Lecture 4.5 Intro to Ions

Welcome back. Let's talk a little bit about ions. So, so far, every atom we've talked about has been a neutral atom, or in other words, the number of protons has been equal to the number of electrons. However, some atoms gain or lose electrons in order to get eight valence electrons in the outer ring. This idea is called the octet rule. Let's take a look. So, some atoms like sodium, which has one electron in its outer ring, group one, loses that electron to become a positive ion or a cation, right? This chemistry sentence here shows that process. Similarly, other elements which have maybe six valence electrons or seven will gain two or one electrons to get eight in their outer ring. Sulfur is an element that does this. Here's some common charges on ions on the periodic table. As you're looking at this and copying down that blue sentence, think about why these elements might form those charges. Remember, group one, sometimes called group 1A, has one valence electron. So, it loses that one electron and becomes a positive ion. Why? Well, lithium originally has three protons and three electrons, a total charge of zero. When it loses one of those electrons, it now has two electrons, negative two, and three positive charges with an overall charge of plus or plus one. One thing you might be thinking here with lithium is why it doesn't have eight valence electrons in that outer ring. And that's okay. That first ring is complete with only two electrons. So, two is a very stable number for lithium ions and beryllium ions to have in their outer ring. What's the symbol for magnesium ion? We'll find magnesium on the table. Magnesium symbol is Mg. It has two valence electrons, so it's gonna form a 2 plus or a plus 2 ion. What's the symbol for an atom with 15 protons, 16 neutrons, and 18 electrons? Well, the number protons identifies the element, so the element with 15 protons is nitrogen. If it has three additional electrons, it has a minus 3 charge. How about an iron 3 plus ion? Well, an iron 3 plus ion, might take you a minute to find iron on your periodic table, has 26 protons. Remember, the plus 3 means it has three less electrons. That's all for ions for now. We're gonna next jump ahead to a future chapter where we're gonna take a look at a little more about electrons.