Alkali Metals: Reaction with oxygen, water, chlorine, hydrogen and acid

Reaction with oxygen
The alkali metals will react quickly with the oxygen in the air to create a white oxide.
e.g.
4K(s) + O₂(g) → 2K₂O(s)
All except lithium react further to form yellow peroxides
2K₂O(s) + O₂(g) → 2K₂O₂(s)

Reaction with water
The alkali metal will react vigorously with water to form a hydroxide and also produce hydrogen gas. The hydroxides dissolve in water to form a basic solution.
e.g.
2Li(s) + 2H2O(l) --> 2LiOH(aq) + 2H2(g)

Reaction with chlorine
The alkali metal will react vigorously with chlorine gas and produce a white crystalline chloride salt.
e.g.
2Na(s) + Cl2(g) --> 2NaCl(s)

Reaction with hydrogen
The alkali metals react with hydrogen gas to form hydrides
e.g.
2Li(s) + H2(g) --> 2LiH(s)

Reaction with acid
Alkali metals react with acid to form a salt and hydrogen gas.
e.g.
2Na(s) + 2HCl(aq) --> 2NaCl(aq) + H2(g)

http://www.bbc.co.uk/schools/gcsebitesize/science/add_ocr_pre_2011/periodic_table/group1rev4.shtml
http://chemed.chem.wisc.edu/chempaths/GenChem-Textbook/Group-IA-Alkali-Metals-544.html
http://wiki.answers.com/Q/What_is_the_reaction_of_alkali_metals_with_an_acid