Write the names of the formulae and the uses of of at least five salts

Below.

Explanation:

Sodium Chloride NaCl.  Cooking.

Calcium Sulphate CaSO4.  Plaster of Paris.

Ferrous Sulphate FeSO4. Iron supplement in medicine.

Magnesium Sulphate. MgSO4. Laxative.

Ammonium Nitrate. NH4NO3. Fertiliser.

the density(ratio between mass and volume as m/v) decreases from top to bottom in periodic table group as the size increases and nuclear charge decreases. but in periods density increases from left to right as atom size decreases and nuclear charge increases.

the mantle

explanation:

earth is divided into three layers: the crust or the outermost layer on which we live; the underlying, middle layer - the mantle - and the core (the innermost layer of earth).