C2.1 Development of the periodic table
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How did John Dalton arrange the elements?
➢ In order of their atomic weights
How do Newlands arrange the known elements?
➢ Atomic weight
What did Newlands notice?
➢ That the properties of every eighth element seemed similar
Why did other scientists ridicule Newland’s ideas?
➢ Newland produced a table showing his law of octaves - he assumes all elements had been found ➢ Did not take account into discovering new ones ➢ Filled his law of octaves even though some of his elements were not similar at all ➢ His pattern only worked for the known elements up to calcium
How did Mendeleev arrange the elements?
➢ In order of their atomic weights ➢ Arranged them so that a periodic pattern in their properties could be seen
What did Mendeleev do?
➢ He left gaps for elements that had not yet been discovered ➢ Then he used his table to predict what their properties should be
How did Mendeleev’s prediction get proven?
➢ A few years later - new elements were discovered with properties that closely matched Mendeleev’s predictions
Why did not all the elements fit in with Mendeleev’s pattern?
➢ Ordering by atomic weights would result in argon ( a noble gas) being in the same group as reactive metals such as sodium and lithium