Periodic table

Compounds can be chemically broken down into the elements of which they are made.​

Elements is a substance that cannot be broken down chemically into simpler substances

Greek philosophers had the idea that the universe was made up of a few basic substances or  element (earth ,air, water and fire​)

Robert Boyle defined an element as a substance that cannot be broken down into simpler material

 Humphrey Davy developed new electrochemical techniques for breaking down compounds into elements​​(Used electrolysis to break down water into hydrogen and oxygen. Isolated potassium and sodium)​

Henry Moseley using x-rays he discovered the number of protons in the nuclei of atoms. Used atomic number to arrange elements.​

In the periodic table elements are arranged in order of increasing atomic number

A column that goes from top to bottom, it's called a group in the periodic table.

The outer electrons are called valence electrons.

Group 1 are called Alkali metals​ (Very reactive​, Low density​, Soft-can be cut with a knife, Burn in air to form oxides​)

Group 2 are called Alkaline Earth metals​ (Reactive​, Harder than group one​, Burn in air to form oxide​, React  with water to form hydroxides​)

Group 7 are called The Halogens​ (Reactive​, Chlorine, Bromine, Iodine​, React with hydrogen to form acids​)

Groups 8 are called The Noble (inert) Gases (not reactive)​

A horizontal row of elements in the periodic table is called a period.

 Dobereiner Traid establish a relationship between the properties of elements and their atomic weights (Cl, Br, I)

newlands Octaves

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