Tuesday, April 21, 2009

Group 2/ halaogens /IGCSE chemistry notes

group 2


* Group 2 elements are known as alkaline earth metals.

* They can form strong alkali and they occur widely on earth crust.

* They are metals.

* They have melting points and densities that are quite low for metals.

* They react with air, water or steam to form oxides and hydroxides.

* They show the same reactivity trend as group 1, increasingly reactive as you go down the group.

* They form compounds in which the metal has a +2 ion.

* They form white or colorless compounds which gives colorless solutions.

* The alkaline earth metals are reactive, but less reactive than the alkali metals.



HALOGENS

* Each of the halogens gives colored vapour.

* Halogens react with hydrogen to form hydrogen halides.

* Halogens react with metals to form metal halides such as iron chloride and sodium chloride, ordinary salt.

* Halogens are oxidizing agents and are themselves reduced.

* Any halogen can displace another that is lower down in group 7.

* We can use ionic equations to show how halogens react.

* Halogens compounds have useful properties.

* They have diatomic molecules X2 .

* They go from gases to liquid to solid as you go down the group.

* They become less reactive towards the bottom of the group.

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