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CHEMISTRY FORM 2


1. STRUCTURE OF THE ATOM, AND THE PERIODIC TABLE
2. CHEMICAL FAMILIES AND PATTERNS IN PROPERTIES
3. CHEMICAL BONDING AND STRUCTURE
4. SALTS
5. EFFECT OF AN ELECTRIC CURRENT ON SUBSTANCES
6. CARBON AND SOME OF ITS COMPOUNDS
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Chemical Bonding and Structure: Oxides of elements in Period 3

3.0 Chemical Bonding and Structure


3.10 Oxides of elements in Period 3


All the elements in Period 3, except argon, react with oxygen to form oxides.


high school chemistry

The oxides of sodium and magnesium dissolve in water to form alkaline solutions. Their ability to dissolve in water decreases sharply from sodium oxide to aluminium oxide, which is insoluble. But they all react with acids to form salt and water only. That is, they neutralize acids. Aluminium oxide reacts with bases as well. It is amphoteric.


An amphoteric oxide (or hydroxide) is one that behaves as a base and sometimes as an acid.


The structure of the oxides is giant ionic in sodium oxide (Na2O) to aluminium oxide (Al2O3, giant covalent in silicon oxide (SiO2, and molecular from phosphorus (V) oxide (P2O5) to chlorine oxide (Cl2O).


Silicon oxide is highly stable (unreactive) and insoluble in water. But the oxides of phosphorus and sulphur are highly soluble, forming acidic solutions (sulphurous and phosphoric acid).


Questions 3.10

  1. Which piece of information given above suggests that silicon oxide has a high melting point?
  2. Phosphorous (V) oxide reacts with water to form phosphoric (V) acid, (H3PO4) as the only product. Write a balanced chemical equation for the reaction.
  3. Phosphorus (III) oxide reacts with water to form phosphoric (III) acid, (H3PO3) as the only product. Write a balanced chemical equation for the reaction.

Answers to Questions 3.10


At home

Silicon oxide absorbs water vapour and is therefore used as a desiccant (drying agent) in suitcases to keep clothes dry and fresh.