History of the periodic table 1

In ancient times, the Greeks believed that there were 4 elements, air, earth, fire and water. In turn, everything else was made up of a mixture of these 4 elements. This was the first notion of elements but didn't advance any further. They were aware of elements such as gold and silver which occurred in nature, but failed to recognise their significance

Hennig Brand was the first person recorded to have discovered a new element. Brand was trying to discover the Philosopher's Stone (a mythical object that was supposed to turn inexpensive base metals into gold). He experimented with distilling human urine until in 1649 he finally obtained a glowing white substance which he named phosphorus. This and related discoveries raised the question of what it means for a substance to be an "element". In 1661 Boyle defined an element as a substance that cannot be broken down into a simpler substance by a chemical reaction.

In 1817, Döbereiner began to formulate one of the earliest attempts to classify the elements. In 1828 he found that some elements formed groups of three with related properties. He termed these groups "triads". Some triads classified by Döbereiner are: chlorine, bromine, and iodine calcium, strontium, and bariumIn all of the triads, the atomic mass of the second element was almost exactly the average of the atomic weights of the first and third elements. This remained the most advanced idea until Mendeleev's periodic table was discovered.

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