This week's science tutorial is about the periodic table of the elements. I assume you already know what the atomic number means, and you understand a little bit about orbitals and electron shells. (If not, go to this video science tutorial).
Anyway, the meaning of the vertical and horizontal placement of an element has always been a source of confusion. This week's science tutorial is an attempt to clear up some of the confusion.
The calendar analogy is my way of trying to connect important science facts with bits of your every day life. In this science tutorial, a period is like a week, and a group is like a day of the week. (Ya gotta love how the noble gasses end up as part of the weekend, while Mondays are highly reactive--potentially explosive.)
As you move further to the right on the table, you'll find that the atomic radius of any given element will usually decrease. This is because the attractive force of the nucleus pulls the electrons tighter in.
The attractive force of the nucleus also leads to a higher ionization energy. The electrons are held in a tight orbit around the nucleus, and it takes more energy to dislodge them and cause a chemical reaction.
In fact, most of this week's science tutorial can be connected directly with the attractive force of the atomic nucleus.
In contrast, as you descend down the periodic table, each element in a group will have a larger atomic radius. This is due to the great number of electrons. They quickly fill up the inner shells, and the remaining electrons have to occupy outer electron shells that are far from the nucleus.
Ionization energy decreases as you descend down the group. The electrons in the outer shells are not held as securely by the attractive force of the nucleus. So they are more likely to be influenced by other atoms.
Keep in mind that there are exceptions to these rules. For example, all of the elements in the f-block behave differently, as well as some of the lightest and heaviest of the known elements. I'm planning to post another video science tutorial about this in the future.
Next week's science tutorial, however, will probably not cover chemistry.