The distant past
Aristotle (384-322 BC) was an ancient Greek philosophers who thought that everything was made up of just four elements: earth, water, air and fire.
Antoine-Laurent de Lavoisier
In 1789, a French chemist Antoine-Laurent de Lavoiser preoduced the first modern chemical textbook which he compiled the first list of elements; oxygen, nitrogen, hydrogen, phosphorus, mercury, zinc and sulfur.
Jons Jakob Berzelius
In 1828, the Swedish chemist Jons Jakob Berzelius published a table of atomic weights, determined the composition by mass of many compounds, and introduced the letter-based symbols for elements.
In 1892, Dobereiner discovered that strontium had similar chemical properties to calcium and barium, and that its atomic weight fell midway between the two.
Nature contains triads of elements where the middle element has properties that are an average of the other two members of the triad when ordered by the atomic weight.
The English chemist John Newlands was the first person to devise a Periodic Table of the elements in order of their relative atomic weights. In 1865, he put forward his ‘law of actaves’-
Any given element will exhibit analogous behaviour to the eight element in the table above
• Newlands’ arrangement showed all known elements in seven ‘octaves’
• The elements are ordered by the atomic weights that were known at the time.
In Mendeleev’s table:
• Elements with similar properties were arranged in vertical columns
• Gaps were left for not found elements
• The order of elements was rearranged where their properties did not fit
Mendeleev’s periodic law:
• The elements, if arranged according to their atomic weights, exhibit an apparent periodicity of properties
• Elements which are similar, as regards to their chemical properties, have similar atomic weights or increase regularly
• The elements which are the most widely diffused have small atomic weights
• The magnitude of the atomic weight determines the character of the element
• Certain characteristic properties of elements can be foretold from their atomic weights