1Periodic Table - B.pdf

The Periodic Table The modern periodic table is a list of elements arranged in increasing atomic number. It is arranged into horizontal periods & vertical groups        Ancient Greeks - Stated there were 4 elements: Earth, Air, Wind, Fire. Robert Boyle - Element cannot be split up into simple...

The Periodic Table The modern periodic table is a list of elements arranged in increasing atomic number. It is arranged into horizontal periods & vertical groups        Ancient Greeks - Stated there were 4 elements: Earth, Air, Wind, Fire. Robert Boyle - Element cannot be split up into simpler substances by chemical means. Humphry Davy - Used electrolysis to break down water into hydrogen and oxygen. Isolated potassium and sodium. Johann Dobereiner- Triads. The elements in a triad has similar chemical properties. The atomic weight of the middle element is half way between the other 2 elements. John Newlands - increasing atomic weights.He found that the eighth element had properties similar to the first. He called these groups octaves. Dmitri Mendeleev -He arranged the elements in order of increasing atomic weight.  Listed in subgroups elements such as Cu & Ag whose properties did not fit into the main group.  Put Iodine & Tellurium out of order of Atomic weight.  Left gaps for undiscovered elements  Predicted the properties of these yet to be discovered elements. Henry Moseley – Arranged by atomic number, not atomic weight. He used X-rays to determine the number of protons in the nucleus of an atom.