Posted on February 7, 2016
Not long ago I wrote about Dmitri Mendeleev's Periodic Table of the Elements. I linked to an interactive table, a video, some cool Periodic Table products, and of course the wonderful Periodic Table song.
So...why is TODAY Periodic Table Day?
As with all scientists, Mendeleev came up with his contribution by “standing on the shoulders” of past scientists who had made earlier contributions. (One of the most respected scientists ever was Sir Isaac Newton, and he once wrote, “If I have seen further it is by standing on the shoulders of Giants.”) That's one of the most marvelous things about science – whatever works is kept, ideas that are disproven fall away, and we hone in little by little to a better, truer understanding of life, the universe, and everything.
Today we acknowledge one of the earlier scientists who noticed the pattern to the properties of elements. On this date in 1863, English chemist John Newlands published one of the first table of elements. At that time, 63 elements were known; Newlands arranged the elements by increasing atomic weight and assigned them atomic numbers that showed that order. He grouped them into 11 different groups and suggested the “Law of Octaves”: any one element has similar properties to elements eight places before and behind it on his table.
Newlands was correct about there being patterns of properties, and he was able to correctly predict an element that was eventually discovered and named germanium. However, at the time he presented his idea, it was ridiculed by many other chemists, and his lecture presenting the idea was not published.
Actually, Newlands arrangement of the elements was not as helpful to chemists and did not make as many accurate predictions as Mendeleev's table, so in my opinion, Mendeleev deserves the credit that he receives. However, Newlands did have some great ideas, and he ended up fighting to receive some credit and recognition after Mendeleev's table was published and praised!
You are hopefully wondering why the chemical elements should follow a pattern of eight.
It's because electrons of atoms can only exist at certain energy levels (and therefore certain distances from the atom's nucleus). And the first several energy levels can hold up to two electrons (in the first shell) or up to eight electrons (in the next two shells). Check out this video.
And the outermost electrons (which are called the valence electrons) are the ones that react with other elements. Check out this video.
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