Year 13 - The oxides of Elements in Period 3 Flashcards
Name and give properties of the metal oxides.
Sodium, magnesium and aluminium. Giant ionic lattices - bonds extend through the complexes, high melting points.
Why is aluminium oxide considered different to the other 2 metal oxides?
The bonding is ionic but has some covalent character - as aluminium forms a very small ion with a large positive charge (Al3+) and so can get close to O2- and distort the electron cloud.
Name the non metal oxides and state their properties.
Silicon oxide - giant covalent, high melting point due to many strong covalent bonds.
Phosphorous oxide - solids, weak van der Waal and dipole dipole IMF, low melting point
Sulfur dioxide and trioxide - gases
Name the basic oxides and highlight how they react with water.
Sodium and magnesium oxides. Sodium oxide reacts with water to form sodium hydroxide which is strongly alkaline.
Magnesium oxide - reacts with water to form magnesium hydroxide, sparingly soluble, somewhat alkaline.
Name the insoluble oxides.
Aluminium oxide and silicon dioxide are insoluble in water.
Name the acidic oxides and describe their reactions with water.
Phosphorous pentoxide reacts violently with water to produce phosphoric (V) acid.
Sulfur dioxide soluble, reacts to give sulfuric (IV) acid. Partially dissociates which causes the acidity of the solution.
Sulfur trioxide reacts violently in water to produce sulfuric (VI) acid.
Why do metal oxides form alkaline solutions?
Sodium and magnesium oxides form ions and so the strong base sodium ion readily reacts with water to form hydroxide ions. Magnesium oxide is less soluble than sodium hydroxide and so forms a weaker alkaline solution.
Aluminium oxide, ionic but the bonding is too strong for the ions to dissociate (partly due to the covalent character).
Silicon dioxide is macromolecular, water won’t affect that structure.
Phosphorous and sulfur oxides react with water to form acid solutions.
What is the general trend for oxides in period 3.
The oxide solutions go from alkaline to acidic across the period.
