This section is on the periodic table so we can use it to help us predict what type of formulas we're going to have and to help us put those formulas together. So just as a review, metals versus non-metals, if you'll see that stair step line that I've put in dark black ink, you may want to go ahead and add that to your periodic table. You'll see that on another couple more images in this section.
And we'll talk more about the left and the right hand side of that on a future slide. But what we find is groups or families are columns with similar properties, and periods are horizontal rows, and they have variable properties. The blocks in the periodic table, the main group elements, are found in columns 1, 2, 13 through 18. We number the columns 1 through 18. because that is the IUPAC convention, the International Union of Physical and Applied Chemists. The transition metals are found in columns 13 through 12, that middle section. There's some post-transition elements, okay, and they're in group 13 through 15 to the right of the transition metals.
And basically there's about six of them. And we're not going to worry too much about them. We just realize sometimes... We have to add something to their name if they're not acting like they would be predicted on the periodic table.
Periods and groups, horizontal rows are periods. So the first period is hydrogen and helium. The second is lithium through neon.
And the third is through sodium through argon. Again, the vertical columns are groups. and by the international union of physical and applied chemist convention we use numbers 1 through 18. so elements within a family have similar chemical properties okay what we're going to find is alkaline metals are are all soft reactive metals noble gases are relatively unreactive gases right they're the few elements that their atoms actually have a charge of zero. So if we kind of take that information we've been just talking about and we can label this, and you can do this in your slide notes, I wouldn't do this in your references, but we need to recognize the alkali metals, the alkali earth metals, sometimes called the alkaline earth metals, the halogens, the noble gases, And we talked about that the horizontal rows are periods and the vertical columns are groups. If we take a look at the metals versus non-metals, notice that diagonal black line separates the, that starts with boron.
And these separate the metals from the non-metals. The problem is those elements that touch that stair-step line except for aluminum. I would assume that we could probably remember that aluminum is a metal and I'm not going to worry too much about the polonium but the rest of them that touch that stair-step line are said to be metalloids because they'll act like a metal in some conditions and then act like a nonmetal under other conditions.
So what we find is the alkaline metals form ions with a one plus charge okay cations alkali earth metals are reactive metals and they form a two plus charge transition metals they have variable charges because they can depending on what conditions they're in they'll either give up one or two or sometimes even three electrons halogens like to gain electrons so they have a one minus charge and become anions and like i said Noble gases are non-reactive metals, or sorry, non-reactive non-metals, and they have a full shell of electrons. Right now, we need to know that they don't want to gain or lose electrons. So to make this information a little bit more useful, I would have you, I would suggest you add that stair-step line to the periodic table in your references. And then put the following charges at the top of the following columns, which is just basically charting out the information from the previous slide.
Put a plus one above group one. a plus 2 above group 2, a plus 3 above group 13, a minus 1 above group 17, a minus 2 above group 16, and a minus 3 above group number 15. And we'll talk about later on in this in the course why they have these charges. We just need to know what their charges are because that's going to help us in the next two sections in the slot notes to write our formulas. Again, this is also what's called a periodic trend because if you notice all the ones in the same column have similar charges.
So if I can ask you a couple questions, it says name a halogen in the fifth period. and that would be iodine and what is the alkali or alkaline earth metal in the third period and that's magnesium what charge do halogens usually have when they form ions that's column number 17 so they're minus one or one minus and do four metals form positive are negatively charged. Well, if you notice everything left of that stair step line has a positive charge at the top of the column.
So this ends the section on the periodic table, and we'll use this information to write formulas in the next two sections.