Chemical Reactivity And The Periodic Table Electron Structure And The Periodic Table: Fill & Download for Free

If you think about the Periodic Table of the Elements it can get pretty mind blowing.First of all there's the whole ordering of the elements. Electron valency, similar properties, etc. It's amazing how it fits together and predicts and that someone could find the patterns with such patchy information. (Dmitri Mendeleev)But that's man-made, imposed structure. Impressive as it is, the underlying structure of the elements themselves is so much more amazing,The defining feature of an element is the number of protons in its nucleus. The first element, Hydrogen, has one proton in its nucleus. Helium, the next, has two. Each time you add a proton you move up one spot on the periodic table to a new element. Sure, other stuff happens too; neutrons come into play, there are electrons to balance the charge. But the only thing that determines the element is the number of protons.Yeah, this is just explaining the periodic table to a five year old, big whoop!Well, what really blows my mind is the changes that occur on the macroscopic (real-world) scale as you add those protons. Hydrogen is chemically completely different to Helium. They're both gases but: Helium is non-reactive, safe and makes your voice go all squeaky; Hydrogen is highly explosive and burns to make water. Add one more proton to Helium and you get Lithium, a metal; solid, shiny and reactive with water.These three players are so different from each other on the large scale and yet, on the atomic scale, they are only one proton away from being each other. And it just keeps getting weirder. Carbon (three more protons up) is the soot from your fire. After that Nitrogen and Oxygen are gases again (though completely different) and Silicon with 14 protons is clear, glassy sand. Each one completely different from it's neighbours in wild and unusual ways.The existence of protons proves that there is an underlying order and structure to these elements (of which there are, not 5, but 118 discrete ones currently) but it is not any order that makes logical sense to my mind. Rather some natural order that produces the ungainly, but brilliant table adorning the walls of science rooms across the world.I don't know. It's a simple thing, maybe. But the more I think about it. The more it blows my mind.

The Groups are columns in the periodic table. Now there are two categories of groups, the main groupe (Roman numeral followed by A) and the transition metals (Roman numeral followed by B). For the main groups, all the elements belonging to a group have the same number of valence electrons and hence a similar chemical reactivity. The transition metals all have a similar electron structure and are not too different one from another when looking at them at a very basic level.

It was the Russian, Mendeleev, in the 1860s, who was mostly responsible for the structure of the periodic table, at a time when only about 60 elements were known.He noticed a number of patterns. For instance, if the elements were arranged according to their atomic masses, he found that just before a very reactive metal (such as sodium), there was an reactive gas (such as fluorine). So instead of writing the elements in a single column, he made a table in which the columns (now called groups) had elements with similar properties. For instance, one group, the alkali metals, had lithium, sodium, potassium, and rubidium. (Cesium hadn’t been discovered yet, I believe).Another column contained the halogens: fluorine, chlorine, bromine and iodine.He found that each alkali metal reacted in a similar matter with each halogen.As he arranged the periodic table, he was able to find ‘holes’ in the table, which he figured represented elements that had not been discovered. Based on their position, he could predict their atomic mass, and some chemical properties.This was a tremendous discovery, and, of course, we still use his periodic table, albeit in a somewhat modified manner.The structure of atoms wasn’t known then, so he did not know about electrons. Later, chemists would find that the electronic structure of the atoms that make up an element determines most of their chemical properties.