الثلاثاء، 12 يناير، 2016

The Group 1 elements




The Group 1 elements
The group 1 elements in the periodic table are known as the alkali metals.
They include lithium, sodium and potassium, which all react vigorously with air and water
The reactivity of the alkali metals increases down the group.
Flame tests are used to identify alkali metal ions in compounds.

The alkali metals

The group 1 elements are placed in the vertical column on the left hand side of the periodic table.
Diagram showing group 1 of the periodic table
Group 1 of the periodic table
Lithium, sodium and potassium are the three group 1 elements you are likely to see at school.
Like all the group 1 elements, they are very reactive.
They must be stored under oil to keep air and water away from them.
group 1 elements form alkaline solutions when they react with water, which is why they are called alkali metals.

Reactions with water

Potassium reacting with water
The reaction of potassium with water gives a lilac flame
Group 1 elements react vigorously with water to produce an alkaline metal hydroxide and hydrogen gas.
In general:
Metal + water → metal hydroxide + hydrogen
For example, here are the equations for the reaction of sodium with water:
sodium + water → sodium hydroxide + hydrogen 2Na + 2H2O → 2NaOH + H2 (the 2s in front of Na, H2O and NaOH are for balancing)
The reactivity of the alkali metals increases down the group. Lithium is the least reactive and potassium is the most reactive of the three. The hydrogen ignites immediately during the reaction between potassium and water with the potassium producing a lilac coloured flame.





http://www.bbc.co.uk/schools/gcsebitesize/science/add_ocr_gateway/periodic_table/group1rev1.shtml

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