Chemistry Period 3 Metals and Oxides

Study Notes

Sodium and magnesium react ionically to form positive ions.
Sodium forms 1+ ions, magnesium forms 2+ ions.
Sodium is more reactive than magnesium because it only needs to lose one electron, while magnesium needs to lose two electrons.
This means that sodium requires less energy to ionize, making it more reactive.
Magnesium reacts slowly with water but reacts violently with steam.
This is because steam provides more energy, resulting in a bright white flame, hydrogen, and magnesium oxide.

Period 3 elements react with oxygen to form oxides with each element in its highest oxidation state.
This number is often the same as the group number.
Sodium oxide (Na2O), Magnesium oxide (MgO), Aluminium oxide (Al2O3), Silicon dioxide (SiO2), Phosphorus pentoxide (P4O10), Sulphur dioxide (SO2) are all examples of period 3 oxides.
The reactivity of each oxide is determined by its structure and bonding:
- Ionic oxides are generally more reactive.
- Simple covalent oxides are also reactive.
- Macromolecular oxides are less reactive.

Oxide structures affect their reactivity and melting points.
Sodium oxide (Na2O) and Magnesium oxide (MgO) are ionic with high melting points and are highly reactive.
Aluminium oxide (Al2O3) is ionic with covalent character, has a high melting point and is less reactive.
Silicon dioxide (SiO2) is a giant covalent structure, highly stable with a high melting point.
Phosphorus pentoxide (P4O10) is a simple covalent structure, reactive, with a low melting point.
Sulphur dioxide (SO2) is a simple covalent structure with a low melting point and readily burns.

Ionic oxides (Na2O, MgO) react with water to form alkaline solutions (pH 10-14).
Simple covalent oxides (SO2, P4O10) react with water to form acidic solutions (pH 0-2).
In solution, these acids dissociate into H+ ions and ions of conjugate base.

Basic, ionic oxides react with acids to produce a salt and water in a neutralization reaction.
Acidic, covalent oxides react with bases to produce a salt and water in a neutralization reaction.
Aluminium oxide (Al2O3) is amphoteric, meaning it can act as both an acid and a base.
As a result, it can react with both acids and bases to form a salt and water in neutralization reactions.