Magnesium
Magnesium is an earth alkali metal, which, in spite of its
electropositive nature can be kept well in a dry place. It is covered by an
oxide layer, which protects the metal for further oxidation. It slowly is
attacked by air, but in practice it can be stored for many years without too
much deterioration. Magnesium is a silvery/grey metal, which is very light,
compared to other metals.
Magnesium metal is an interesting metal for the home lab. For some purposes small turnings or ribbon are most suitable, for other purposes, the powder form is more suitable. Magnesium metal frequently is available on eBay, sometimes as a single 1 lb block, sometimes as turnings and sometimes as powder. Ribbon and turnings are not really risky. The powder form is quite dangerous, when handled carelessly. Ribbon or turnings can be burned with an intense bright white flame, but these are not so easily ignited.
Powdered magnesium
is very flammable and once it burns, it is hard to stop the fire. Burning
magnesium continues burning in carbon dioxide and reacts violently with water!
If possible, then it would be nice to have some magnesium available for the home lab. Many interesting experiments can be done with this. It can be used to make hydrogen in a convenient way, it can be used in some interesting dry chemical experiments (a nice example is given here) and it can be used for interesting pyrotechnic effects.
Compounds of magnesium only are of limited value for the home lab. Magnesium ion is quite unreactive. The metal only exists in the +2 oxidation state in its compounds. Magnesium ion is colorless and does not have extensive coordination chemistry. Magnesium forms precipitates with hydroxides and carbonates and with many other anions.
A cheap compound of magnesium, which is soluble in water is magnesium sulfate, MgSO4·7H2O. This can be purchased in most drugstores. It is a white, somewhat transparent crystalline compound.