History of the periodic table Flashcards
In the early 1800’s, what were the two ways to categorise elements?
- Their physical and chemical properties.
- Their relative atomic mass (the only thing they could measure).
When was it realised that elements were best arranged in order of atomic number?
In the 20th century after the discovery of protons and electrons.
What was John Newland’s attempt at arranging the elements called?
Newlands’ law of octaves.
When did Newlands attempt arranging the elements?
1864.
Why was Newland’s attempt called Newlands’ law of octaves?
Because he noticed that every eighth element had similar properties, so he arranged his table in rows of seven.
Why did Newland’s pattern break down on the third row of his table?
Because transition metals such as titanium and iron did not fit the pattern.
Why did the chemical society criticise Newland’s idea in 1865?
- His groups contained elements that didn’t have similar properties, e.g. carbon and titanium.
- He mixed up metals and non-metals, e.g. oxygen and iron.
- He didn’t leave any gaps for elements that hadn’t been discovered.
When and where did Dmitri Mendeleev arrange his table of elements?
In 1869, in Russia.
How did Mendeleev arrange his table?
- In order of atomic mass.
- He found that he had to leave gaps in order to keep elements with similar properties in the same vertical columns (known as groups).
- He left very big gaps before the transition metals come in on the third row.
Why were the gaps Mendeleev left clever?
Because they predicted the properties of so far undiscovered elements. When they were found they also fitted the pattern.
