Unit 3 chemistry

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  • Created by: Rebecca F
  • Created on: 05-03-13 18:11

The Modern Periodic Table

 The Modern Periodic Table:
John Newlands:
 - Tried listing the elements in order of atomic mass.

- Every eighth element was similar, but  the pattern broke after the first 15.

Dmitri Meneleev:
 - He left gaps in his table so similar elements always lined up.

- He even predicted properties of missing elements, his theory was accepted when his predictions were proved accurate.

We now know that the periodic table is related to the structure of the atoms of each element. They should be arranged according to their atomic numbers, not masses.

The Law of Octaves:  If the chemical elements are arranged according to atomic weight those with similar physical and chemical properties occur every 8 groups.

The law of triads:  Nature contains triads of elements where the middle element has an average of the other 2 elements when ordered by atomic weight. E.g. lithium, sodium, potassium.

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