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Periodic Table

8. Watch and listen to the video.     

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0:14 Our Earth is a collection of puzzle pieces that make up the universe.
0:17 In the vast darkness of space, the universe is lit by stars,
0:21 which could one day become a supernova
0:23 and create all the puzzle pieces that we know today as the elements.
0:27 All elements were formed and released
0:29 into space by exploding stars.
0:31 For centuries, humans have tried to discover
0:33 what makes up the world around them.
0:34 Little did they know that all the pieces they needed
0:37 were right under their noses.
0:39 The discovery of these pieces revolutionized
0:40 our understanding of the world
0:42 and allowed for the creation of what might be
0:44 the greatest gift to science: the periodic table.
0:47 So, where are these elements,
0:49 and how do we find a means to order them?
0:52 Well, believe it or not, ancient civilizations were very much aware
0:55 of many elements around them,
0:57 but they did not identify them as the pieces of our universe.
1:00 Elements like gold, silver, and copper
1:02 were easily spotted by ancient cultures,
1:04 and were used for multiple purposes like jewelry and tools.
1:07 Why were these elements spotted so easily?
1:10 Think of the periodic table as a puzzle.
1:12 The corner pieces are edges of a puzzle,
1:14 are generally the easiest to find and place
1:16 because they stand out with their smooth edges,
1:18 and clearly don't interlock with other puzzle pieces.
1:21 Like puzzle pieces, elements can be choosy on who they interact with.
1:25 Some like to react with other elements,
1:27 while others do not.
1:29 The elements that do not interact with other elements are easy to pin-point,
1:32 while the ones who like to interact with others are difficult to find.
1:35 Gold, silver, and copper are some of the choosier elements
1:39 so we can find them easier.
1:41 So let's fast forward to the late 1600's
1:43 where Hennig Brand, a German alchemist,
1:46 was busy working in his laboratory.
1:47 Like many other alchemists of his time,
1:49 Brand was trying to extract gold from the human body.
1:52 Brand hit upon what he thought was the most obvious answer to his problem: urine.
1:58 Urine is gold in coloration and could perhaps have gold in it.
2:01 So, Brand collected as much urine as he possibly could,
2:04 much of it being his own,
2:06 then he decided to boil it down in hopes of obtaining gold.
2:09 So Brand boiled his, well, urine, down until he collected a paste
2:13 and heated the paste to a very high temperature.
2:16 Eventually smoke appeared and the material burned brightly and violently.
2:20 Brand had unknowingly isolated phosphorous from his urine.
2:23 It was the first time anyone had discovered an element,
2:26 but he didn't really understand what he had done.
2:28 At the time of Brand, the concept of element had not been discovered.
2:32 Instead ancient Greek principles of objects being composed of earth, water,
2:36 air, and fire were predominant.
2:39 It wasn't until the work of Antoine Lavoisier,
2:41 who is now known as the father of chemistry,
2:43 that science defined what an element was.
2:46 Lavoisier defined an element as a substance
2:48 that cannot be broken down by existing chemical means.
2:52 Lavoisier created a list of the known elements of his time
2:54 and tried to put the elements in some sort of order
2:57 in which they could be classified, such as gases or metals.
3:01 He was the first one to try to put the puzzle together.
3:03 This was just the beginning of a means
3:05 to organize the known elements of his time.
3:07 Many other chemists then came along to make the puzzle clearer.
3:10 One of them, John Dalton, weighed the elements
3:13 and arranged the puzzle by weight.
3:15 German chemist Wolfgang Döbereiner later combined elements
3:18 to see how they reacted with one another.
3:21 What he found was that certain elements shared similar properties and reactions.
3:24 For example, when pure lithium, sodium, and potassium
3:28 are exposed to water, they will react violently
3:31 and skid across the surface of the water with sparks.
3:34 The scientists then realized that these similiaritiesare no coincidence:
3:37 elements belong to families that share similar properties.
3:41 But the chemist who finally put the puzzle together is Dmitri Mendeleev.
3:45 He created cards of each known element and tried to order them
3:47 based on atomic weight and their known properties.
3:50 The story is that he stayed up 3 days and 3 nights,
3:53 and he finally fell into a deep sleep
3:55 and he dreamed about a table to order the elements.
3:57 Mendeleev was not only able to create the periodic table,
4:00 but he was able to predict elements that were not yet discovered.
4:03 The puzzle of the periodic table of the elements was solved.

Now, we are going to study its structure. Let's go to the new tab called: "What is the periodic table?"

Short url:   http://multidict.net/cs/2846