Chemistry Topic 1

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  • Created by: Hannah
  • Created on: 28-10-12 11:53

In 1817, Johann Dobereiner, a German chemist, proposed his law of triads. He saw that calcium, barium and strontium had similar properties as did bromine, chlorine and iodine. He proposed that similar elemts exisist in groups of three called Triads. Elements did seem to come from families but not enough to support his theory.

In 1863, English man John Newlana proposed his law of Octave. He noticed that if the elements were written in order of their atomic mass every eighth element has a similar property. Newlans was ridiculed, but he had noticed an underlying pattern that would later form the basis of the modern periodic table.

Dmitri Mendeleev enjoyed playing cars. He grouped the elements with similar properties and did not strictly follow the order of atomic masses. He presumed that some of the atomic masses had been incorretly calculated and moved some elements to make sure that ones with similar properties were kept together. He also realized that there was more elements to be discovered and left gaps in the table.

In 1800's scientist has no clue on the structure of atoms, but they could measure the relative atomic mass.

When all elemens were put in order of their relative atomic mass, they noticed a periodic pattern in the properties of the element.

Since then, new elements have been found which fit into the gaps left in Mendeleev table e.g. scandium, gallium and geranium and a whole new group of elemtns have been discovered and added to the table. The noble gases.

The nucleus is in the centre of the atom and the neutrons. The nucleus is positively charged as the protons are positively charged whilst the neutrons have no charge. Most of the mass of the atom is concentrated in the nucleus however it is very small compared to the rest of the atom.

Electrons move around the nucleus and have…

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