Importance of the periodic table.
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#1
December 28th, 2007, 06:42
 nuke Junior Member Join Date: Dec 2007 Posts: 1
Importance of the periodic table.

I have an assignemt to do and i have written 1050 words on the history and info about the table but i have nothing to write on why it is so important. I know a few things but i need more facts to write them out.

can anyone help?

This is the first assignment i've ever done and i'm proud about the 1050 words but i need another 600!
#2
December 30th, 2007, 11:10
 Hix3r Member Join Date: Apr 2007 Location: Hungary Posts: 40

The periodic table was invented by Dimitri Mendeleev in 1869. This is the history part.

Anyway the periodic table is an awesome thing. When you look at it, it tells you more than you need to know. So it is basically divided into 7 rows and eighteen columns. Now when you look at it the rows are the periods, and columns are groups. The period tells you which shell with the highest energy is being used by that atom. So every atom in the third period aka the third row is using up to the third shell of their shells of electrons. This outer layer is also called the valence shell. In quantum mechanics these shells are marked with letters from K. So the third shell is M.

Then you can see instantly how many valence electrons are in that atom. If it is in the first group it has one, in the third it has three etc. It is really easy. Now the atomic number elements have tell you how many protons are in that atom, which tells you how many electrons are in that atom is its relative charge is zero. Now you also see the standard atomic weight of the element which tells you how many neutrons are in that element. Well how?

The relative weight of the protons are one the neutrons weight is also one, the electron's is 1/2000. So if you have the helium for example. Atomic number 2, standard atomic weight 4. So it has two protons, and two neutrons nad two electrons if it is not an ion. Wow. And that was just from looking at it. Now there is more to this.

The eight group is called the noble gases. Why noble? Because the don't like other elements company. They are the hardest ones to force into a reaction. Why is that? They have the perfect combination of electrons and protons, all of their shells are completed, nothing is missing. all of the other elements are trying to reach this state as well, that is why they go into a reaction and pull an electron, or give an electron away, this way they will be closer to this state. (Not so different from our lives, noble ones are hard to make contact with.)

The seventh group are the halogens. They are one electron short from noble gas state, so they are doing everything to get one electron. They are the most eager ones to form a reaction and get a hold of an electron.

The sixth called the oxigen group, fifth the nitrogen, fourth the carbon, the third is a tricky one because the first one boron has metalloid attributes. Right under the aluminium is a metal. So the border is from boron to Astatine. This line goes through the element that are metalloid elements. Below it are the metals, above the non-metals.

The first group is the alkaline metals second one is the earth alkaline metals. Now there are the eight main groups. The ones inside are the transition elements. They are different form the main groups because in them the d subshell starts to get electrons. Because of this they have very different attributes. Also here you can find jumps in the atomic numbers. Well there is the point where the two rows below the table come in play.

In these two rows (upper one is Lantanides lower is Actinides) you will find the ones where the f subshell is filling up with electrons, and again because of this they have different attributes. But this was the only way to make this work because they d subshell remain the same.

In some tables you can also read the exact electron configuration, the state of the element is normal circumstances, the electronnegativity.
As you can see the atomic number is always increasing from left to right, this is the same with atomic mass, but the diameter of the atom is increasing in groups from up to down.

Now these are just bits and pieces, if you want information, why don't you try wikipedia?
http://en.wikipedia.org/wiki/Periodic_table

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