As you learn chemistry, the periodic table is the most important tool you'll use. A calculator is a close second, but you could probably work the math by hand if you had to. I've been doing chemistry for years and still rely on a periodic table all the time. In this video, we'll go over a few terms that you'll need to be familiar with so that we can efficiently use the periodic table. First up, we see that the table is divided into rows. Each row is called a period and is numbered from 1 to 7. The periods are arranged so that many properties of the elements increase or decrease fairly smoothly as you read from left to right. If you look towards the bottom of the table, you'll see that the two rows that sit apart from the rest of the table are color coded to match the sixth and seventh periods. You may be asking why that is, why those elements sit out by themselves. There's a reason for that coloration. This shown here is a long form periodic table. The elements that are usually down at the bottom are placed into the table in their proper positions. The problem with the long form table is that it's hard to fit on a single sheet of paper with text large enough to easily read. So most periodic tables pull those two rows out leaving the format that you're more used to. The columns of the periodic table are called groups or families. Most properties increase or decrease smoothly as you move down a given group, just like they do going from left to right along a given period. There are two numbering systems for the groups. And most periodic tables include them both. The standard numerals 1 through 18 can be used, starting at the left and counting towards the right. The elements that are separated out at the bottom of the page don't have group numbers. They're really weird, rare elements. And so we can sort of pretend that they don't exist right now. The older numbering system involves Roman numerals from 1 to 8, along with an A or B designation. In this color scheme, the Boulder groups, which are the first two and last six groups, are numbered 1A through 8A. The middle groups colored in sort of pastels are numbered 1B through 8B. The numbering gets funky there in the middle, especially where there's three columns are all designated as 8B. The advantage of the Roman numerals system, even if the numbers are super weird, is that the A and B designations are really useful. Everything in an A group can be called a main group or representative element. Everything in a B group is a transition metal. When we talk about the periodic properties and their trends, we're going to focus on our representative elements. This version of the table highlights the metallic nature of the elements. The purple elements along that diagonal are known as the metalloids. Elements above and to the right in blue are nonmetals. And elements below and to the left are metals. The only exception to this is hydrogen, the smallest element. It is placed above lithium, firmly on the metal side of the table, even though it is in fact a nonmetal. Hydrogen is small enough that it can behave in some interesting ways. And so even though it's a nonmetal, it acts more like lithium than fluorine, so it goes on the left. In general, metals are shiny, malleable, which means they can be hammered into sheets. They're ductal, which means they can be drawn out into wires and they're conductive. Nonmetals tend to be brittle and dull, and they don't conduct heat or electricity very well. The metalloids have a wide variety of properties, and things like their conductivity can change depending on the conditions. The last bits of vocabulary you should know are the names of a few special groups. The group one elements with the exception of hydrogen are collectively known as the alkali metals. They are incredibly reactive and not found in nature by themselves. The group two metals are the alkaline earth metals. They are also pretty reactive, but somewhat more stable than the alkali metals. On the right side of the table, group 18 contains the elements known as the noble gases. These gases are almost completely non-reactive, and in fact were among the last elements discovered, because early elemental discoveries involved novel reactions. Group 17 elements are called the halogens, and most of these are diatomic, which means that if you find elemental chlorine, for example, you'll find two chlorine atoms chemically bonded together instead of individual separate chlorine atoms. The lighter brown elements in the middle there are the transition metals, just as I mentioned before. The two rows down at the bottom are commonly called the inner transition metals. There are many other names and subdivisions that can be applied to the periodic table, but what I've just covered are a few of the most common. You should also be aware that while most periodic tables are presented in a two-dimensional grid, that's not the only way to illustrate the periodic nature of the elements. Shown here is one example of a spiral table. It's got hydrogen in the center, and the yellow wedge contains the noble gases. The halogens are on one side of the noble gases, and the alkali metals are on the other. The standard grid format suggests that halogens are closely related to noble gases, and alkali metals are very far removed from the noble gases. The spiral arrangement shows a little more clearly that halogens and alkali metals are related to the noble gases in very similar but opposite ways.