The periodic table of the elements is sorted as it is (in row-like periods and column-like groups) because of the number of free/occupied valence electrons, which is the number one factor in determining each atom’s chemical properties. Atoms can link up to form molecules in tremendous varieties, but it’s the electron structure of each one that primarily determines what configurations are possible, likely, and energetically favorable. Prior to 2003, bismuth was designated as the heaviest stable element; today, we know it’s inherently unstable. (Credit: Adobe Stock)

The periodic table you grew up with is wrong

Up until 2002, we thought that the heaviest stable element was bismuth: #83 on the periodic table. That’s absolutely no longer the case.

As we came to observe the Universe on smaller and more fundamental scales, we began to discover what the building blocks of matter were. Macroscopic materials are made up of smaller components that still retain the physical and chemical properties of the larger original. You can break things down into individual molecules, and still those molecules will exhibit the same behavior in isolation as they did when they were part of the larger structure. Molecules can be broken down further, into individual atoms, which still retain the same binding properties they possessed when they were in molecules: evidence that there’s something very important, on the atomic level, for building up the larger-scale structures in our Universe today.

We eventually came to recognize that atoms have properties that can be sorted, periodically, by the number of protons in their nucleus. The positive charges in the nucleus determine how many electrons must orbit that nucleus to make an electrically neutral atom, and then the behavior of those electrons, according to the laws of quantum physics, determine how those atoms behave, interact, and…