Chemistry (Salters) Skills for Chemistry: Open-Book Paper - The Periodic Table.

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Chemistry (Salters)

Skills for Chemistry: Open-Book Paper

The Periodic Table is a matrix in which known elements are arranged in order of increasing atomic number. Elements with similar properties are placed under one another in columns, of which there are 8 groups. Each group shows an order of chemical and physical properties, from group 1, to group 8.

Antoine Lavoisier was the first scientist to define a chemical element, immediately upon doing so applied 33 of those known into a table for the publication of his book in 1789. Within his table, the ‘elements’ were grouped into four categories in relation to their chemical properties. These were: gases, metals, non-metals and earths. As technology began to develop over the years, more reliable theories were devised in order to characterise and present elements.

By the early 19th century German scientist Johann Dobereiner produced his law of Triads. This was key to the development of the modern day Periodic Table. Dobereiner grouped elements based upon similarities. Taking the three elements calcium, strontium and barium, he noticed the atomic weight of strontium fell midway between that of the other two.

, ,     (40 + 137) ÷ 2 = 88

From this, more triads were found. In 1829 Dobereiner published the law of triads. From this, scientists established that chemical relationships extended beyond triads and atomic masses. This has developed further into what forms groups in the modern Periodic Table.

Alexandre Beguyer de Chancourtoise of Paris first produced a table involving this, listing the elements periodically. The ideas were complex and his graph was designed spherically. It wasn’t until Mendeleev’s discovery that his ideas were taken seriously.

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In 1863, English chemist John Newlands wrote of his discovery about the law of octaves. Charting the 62 known elements in order of mass, he noticed the repeated physical and chemical properties of each, every eighth element (the noble gases were yet to be discovered). Thus, creating the ‘first’ periodically listed table of elements.

In 1869, Russian scientist Dimitri Mendeleev also arranged the elements by atomic weight and their properties. During 1871, he revised his original 17-group table, into 8 columns, of which the eighth were transition elements. Not only did Mendeleev’s periodic table comprise of Dobereiner’s ...

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