In the third and final part of our series about the periodic table of elements, Everyday Einstein explains just what is periodic about the periodic table.
In Part 1 of this series on the periodic table, we looked at the information contained in each block of the periodic table of the elements. These included things like the atomic number, chemical symbol, and atomic weight of each element. I also mentioned that these blocks of elemental information are arranged in columns called groups and rows called periods.
In Part 2 of the series, we looked at how elements in each column or group share some common properties. Today, in our third and final part of this series we’re going to look at the rows each element is arranged into in order to determine just what’s so periodic about the periodic table.
Before we really get into the details of the chemistry that we’re going to look at today, I need to get something off my chest. The truth is that the periodic properties of the periodic table aren’t really all that periodic. You see, normally in math and science, something that is periodic repeats its values at regular intervals. And just like the exceptions to the properties of elements in certain column groups that I mentioned in Part 2, things aren’t quite as perfect as textbook table artists would like you to believe.
Don’t Be So Negative
The first periodic trend in the periodic table that we’ll look at is called electronegativity. I mentioned electronegativity briefly in my episode on atomic bonds, but in case you’re the kind of person who doesn’t like to dwell on negative things, electronegativity can be thought of as the measurement of how good an atom is at hoarding electrons. For example, chlorine is more electronegative than sodium, so when they get together, chlorine grabs sodium’s lone valence electron in order to complete its collection.
Starting at any given point in the periodic table, electronegativity increases as you move to the right and decreases if you move down. Except when it doesn’t...