KS 3 Chemistry The periodic Table

In this video we're going to learn about the periodic table. So we'll cover what the periodic table tells us about the structure of atoms in different elements, how the table organizes elements into metals and nonmetals, what groups and periods are, and then also how patterns in reactions can be predicted using the periodic table. Let's begin by looking at what the periodic table tells us about different elements. Now the periodic table organizes all of the known elements, and everything in the universe is created from different combinations of the elements in this table. Each element is shown in separate box. So for instance, this box shows copper, and this one shows oxygen. If we use sodium as an example, we can see that every box contains three pieces of key information. Firstly, we can see the one or two letter symbol for each element. In this case, it's Na, which stands for sodium. Next, we can also see the number of protons each atom of that element has. Then lastly, we can see this larger number here, which tells us the total number of protons plus neutrons in an atom of that element. So now let's move on to see how the periodic table organizes elements. Just like book, the periodic table is read from left to right and from top to bottom, with the elements arranged in order of an increasing number of protons. Sometimes you might see zigzag line running along here, and this line separates the metals, shown here in orange, from the nonmetals, here on the right, shown in blue. Now the table's organized into vertical columns called groups and horizontal rows called periods. So starting on the far left, we have group one, then groups two, three, four, five, six, and seven. And then at the end, rather than group 8, it goes to group 0. Group 1 elements are known as the alkali metals, whilst group 7 are the halogens, and group 0 are the noble gases. This block in the middle here are all metals, but you don't need to worry about their group numbers, so just remember to skip them when you're counting your groups. Then to finish up, let's take look at how patterns in reactions can be predicted using the periodic table. The first thing to know is that the elements within group usually all have similar chemical properties. As an example, all the elements in group 1 here react strongly with water, and they're all soft and shiny. Meanwhile, all the elements in group 0 are really unreactive, which basically means that they're very unlikely to react with anything else. There are also patterns within groups, though. In the case of group 1, they become more reactive as you go down the group. What this means is that even though all the elements are reactive, the elements lower down in group 1 react much more strongly than those higher up in the group. For instance, when lithium reacts with water, it just fizzes bit, but when rubidium reacts with water, it explodes violently. On the other hand, if we look at group 7, the elements become less reactive as you go down the group. So, fluorine is the most reactive, while astatine is the least reactive. If you haven't heard yet, you can find all of our videos on our website, cognito.org. You'll also find questions, flash cards, exam-style questions, and past papers. And we track all of your progress, so that you always know what to study next. So, sign up for free by clicking here, or browse our playlist here on YouTube. Mhm.