
The periodic table was created by Dmitri Mendeleev in 1869, simply for the convenient use of elements. The vertical "columns" are called groups, because elements of each vertical column are of the same group. Whereas the horizontal rows are going in order from smallest atomic number to largest. Starting at the top left with hydrogen, and then to the top right with helium. Then on to lithium and beryllium. It then keeps going until you hit the man made " group" referred to as the "unun" group (ununtrium, ununium, ununquadium, etc.). It has all 118 known elements on it, missing numbers 113, 115, and 117. Making it a total of 115 elements actually known to mankind. Although I'm sure that they have found the missing numbers, and possibly more than that. But, they haven't quite updated the commonly known periodic table yet. I'm sure they probably will after a while, but as for now they have not. Tom Lehrer wrote a song about it in 1959, which only contains about 102 of the elements, but it is understandable considering that only about 102 elements were actually discovered in 1959. Here is the song -->
http://youtu.be/DYW50F42ss8. The song actually has no relations to the order of the periodic table, it does list many of the elements. The periodic table is well-organized to say the least. There are a couple of ways to divide the periodic table, starting with horizontally, stated above. but there is another way, vertically. Starting with the far right, those are the Alkali metals, and a noble gas (Hydrogen). The Alkali metals all have some of the same characteristics, such is why they happen to be in the same group. All of the Alkali metals are similar in that all of their outermost electrons lie in the s-orbital. Also, this group of elements is located in the s-block of the periodic table. Right next to the next group, the Alkaline earth. These 2 groups make up the S-block on the periodic table. These are similar because of the freakishly high melting point, and that they would remain as "solid earth metals" in a fire. Not to mention that most of the Alkaline earth metals have a specific flame color when lit ablaze. Well, besides beryllium and magnesium of course. Calcium burns orange, Strontium burns bright red, barium burns green, and radium burns crimson red. There is another that will go into the alkaline earth metals, which is Unbinilium (Ubn). Although they have to synthesize it first, which is proving extremely difficult, it may be added soon. Those are only the first 2 groups, although group #'s 3-12 consist of the transition metals. They are a big category, so i think that we will come back to them later. one thing you may have noticed in the periodic table, is that there is a diagonal line between groups 13 and 16. Starting with Aluminum, and going all the way down to titanium. Then over 2 elements to Bismuth, then it goes diagonally upwards, including the elements of Tin, and Gallium. Those elements are known as the post-transition metals, all 7 of them. And directly after that, comes the metalloids.This group consists of Boron, Silicon, Germanium, Arsenic, Antimony, tellurium, and Polonium. These metals show characteristics of both metals and non-metals, so they are the "half-way" elements. They show some characteristics of both elemental "categories" (metals and non-metals).

So, we simply label them the metalloids, or Semimetals. After the metalloids come the Non-metals, which consist of pretty much all the gases. In reality its anything and everything that isn't a metal. Which is pretty much everything on the right side of the metalloids. So, the diagonal line that i told you about earlier, its everything that is on the other side of that. The nonmetals are divided into a couple groups (halogens, noble gases, and other non-metals). The "other" non-metals consist of carbon, trogen, oxygen, phosphorus (below nitrogen), sulfur (below oxygen) and Selenium (blow Sulfur). they arnt halogens, or noble gases. Yet they aren't metals, so we call them the "other" non-metals." Then are the halogens, which contains all three normal states of matter (gas, and liquid). The halogens include fluorine, bromine, chlorine, iodine, astatine, and the new element, temporarily named ununseptium. Halogens are extremely reactive, and are only found in nature as compounds and ions. This category is in the P-block, right in between the noble gases, and non-metals. To be more specific they are group 17, all of them. On the other side of the halogens, are the noble gases, which are also in the p-block. These consist of helium, krypton, radon, neon, argon, xenon and quite possibly ununquadium. Pretty much all of these elements are non-reactive, colorless, odorless, monatomic gases. We are now going to skip back a little bit to the lanthanoids and actinides. We shall start with the lanthanoids. They are located in group 3, and includes all the elements between the atomic numbers of 57-71, and are somewhat sectioned off towards the bottom of the periodic table. Right below the lanthanoids are the Actinides, which include elements of the atomic #'s 89-103. These elements are considered to be the inner transitional metals (lanthanoids and Actinoids). Now we will revisit the Transitional metals, which make up most of the periodic table. They go from group 3 to group 12. covering periods 4-7 (excluding the inner transitional metals). All of these are located in the d-block, meaning that all of their electrons go out to the d-orbital. Although many transition metals are somewhat reactive, although many of these metals' inner d orbital has more energy than the valence-shell s orbital. That there would rap up the entire periodic table...
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