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!
Why...?
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.
Also
on this date:
Plan
ahead:
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out my Pinterest boards for:
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