The periodic table ended the age of alchemy and gave birth to chemistry. I wish to show you what the periodic table is, a little of its history, what it does and why it is so important.
Before we start here is some definitions:
- · Element – the simplest form of a substance; i.e. the building basic block.
- · Proton and neutrons – the smaller particles found in middle of atoms.
- · Atomic number – number of protons
- · Mass number – number of protons + neutrons
- · Atom – the building blocks for everything; one atom in an element*
- · Period – the proper name for the rows in the Periodic Table.
- · Group – the proper name for the columns in the Periodic Table.
Way back in 1869 a little known Russian chemist called Dmitri Mendeleev arranged all the known "elements" in order of increasing atomic number. The discovery was beyond belief. Mendeleev had managed to construct a table of all the elements with knowledge of just under half of them. He managed to leave space for the elements not even yet discovered. Well that's the history.
Now for the science. Below is the Periodic Table of Elements (shorted to Periodic Table normally) - I thought this picture shows it quite nicely. Do you think?
Each element on the Periodic Table is represented by a symbol. For example the first column (called the alkali metals) read from top: Hydrogen, Lithium, Potassium, Rubidium, Cesium and Francium. When writing the symbol remember: the first letter is a capital and the second is lower case.
The periodic table can be divided into two, if you draw a diagonal line between the yellows and the light greens on the right you find everything on the left of the line is a metal and everything on the right of the line is a non-metal.
Here it gets a little fiddlier: ignore the yellow part in the middle of the second table below.
The numbers refer to group number - the number lets us work out how they react. The number is actually referring to the number of electrons (see definition above) in the outside of the atom with 0 actually meaning 8.The outer layer of an atom is called the outer energy level.
The aim of all the numbered groups is to have the same number of outer electrons as group 0 which is 8. To do this they must either react to gain or lose electrons. The table this shows this:
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Group:
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1
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2
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3
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4
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5
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6
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7
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0
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Loss/gain of electrons.
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1
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3
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4
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3
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2
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1
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0
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The elements in group 1-3 gain electrons to have the same number of outer electrons as group 0.
The elements in group 5-7 lose electrons to have the same number of outer electrons as group 0.
Group 4 either gain or lose electrons.
Well, that's a basic look at the periodic table and how it is put together. I have tried to keep it simple- don't worry if you can't understand the last part.
Connor Davidson 05/02/09
Pic credits: BBC
