What are Electronegative and Electropositive atoms?
We know that an atom can gain, lose or share electrons when forming a compound. Based on this behaviour, atoms can be classified as electronegative and electropositive atoms.
An atom that has a tendency to gain electrons and acquire a negative charge is known as an Electronegative atom.
An atom that has a tendency to lose electrons and acquire a positive charge is known as an Electropositive atom.
Writing the chemical formula for compounds (Give and Take of electrons)
Valency of elements chart
| Name of Element | Symbol | Valency |
| Hydrogen | H | 1 |
| Helium | He | 0 |
| Lithium | Li | 1 |
| Beryllium | Be | 2 |
| Boron | B | 3 |
| Carbon | C | 4 |
| Nitrogen | N | 3 |
| Oxygen | O | 2 |
| Fluorine | F | 1 |
| Neon | Ne | 0 |
| Sodium | Na | 1 |
| Magnesium | Mg | 2 |
| Aluminium | Al | 3 |
| Silicon | Si | 4 |
| Phosphorus | P | 3 |
| Sulphur | S | 2 |
| Chlorine | Cl | 1 |
Magnesium chloride
The symbol for magnesium is ‘Mg’ and chlorine is ‘Cl’. The valency of magnesium is 2 and it is electropositive in nature. Hence, the charge on magnesium ion is 2+. The valency of chlorine is 1 and it is electronegative in nature. Hence, the charge on a chloride ion is 1-.
This means that 1 magnesium ion combines with 2 chloride ions to form magnesium chloride.
Hence, the chemical formula for magnesium chloride is ‘𝑀𝑔𝐶𝑙2’.
The chemical formula for magnesium chloride
Aluminium oxide
The symbol for aluminium is ‘Al’ and oxygen is ‘O’. The valency of aluminium is 3 and it is
electropositive in nature. The valency of oxygen is 2 and it is electronegative in nature. Hence, the charge on an aluminium ion is 3+ and that on oxide ion is 2-.
This means two aluminium ions combine with three oxide ions to form aluminium oxide. Therefore, the chemical formula for aluminium oxide is ‘𝐴𝑙2𝑂3’.
The chemical formula for aluminium oxide