Atoms, Molecules & Ions
The Building Blocks of Matter | Basic Concepts of Chemistry
1. The Atom
Atoms are usually electrically neutral. They consist of subatomic particles: Protons ($+$), Neutrons (neutral), and Electrons ($-$).
Examples: Hydrogen ($H$), Oxygen ($O$), Iron ($Fe$), Neon ($Ne$).
2. The Molecule
A molecule is the smallest particle of a pure substance (element or compound) that can exist independently and retains all properties of that substance.
It is formed by the chemical combination of two or more atoms.
Types of Molecules
- Homoatomic Molecules (Elements): Made of atoms of the same element.
Examples: $O_2$ (Oxygen), $O_3$ (Ozone), $P_4$ (Phosphorus), $S_8$ (Sulfur). - Heteroatomic Molecules (Compounds): Made of atoms of different elements combined in a fixed ratio.
Examples: $H_2O$ (Water), $CO_2$ (Carbon Dioxide), $CH_4$ (Methane).
Atomicity
The number of atoms present in one molecule of a substance.
| Type | Atomicity | Examples |
|---|---|---|
| Monoatomic | 1 | He, Ne, Ar (Noble gases) |
| Diatomic | 2 | $H_2, N_2, O_2, HCl$ |
| Triatomic | 3 | $O_3, CO_2, H_2O$ |
| Polyatomic | > 3 | $P_4, S_8, CH_4$ |
3. The Ion
An ion is an atom or a group of atoms that carries a net electric charge (positive or negative) due to the loss or gain of electrons.
Types of Ions
- Cation (Positive Ion): Formed by the loss of electrons from a neutral atom (usually metals).
Formula: $Na \rightarrow Na^+ + e^-$
Examples: $Na^+, Mg^{2+}, Al^{3+}$. - Anion (Negative Ion): Formed by the gain of electrons by a neutral atom (usually non-metals).
Formula: $Cl + e^- \rightarrow Cl^-$
Examples: $Cl^-, O^{2-}, N^{3-}$.
Polyatomic Ions
A group of atoms carrying a charge is called a polyatomic ion.
Examples: Ammonium ($NH_4^+$), Sulphate ($SO_4^{2-}$), Nitrate ($NO_3^-$), Hydroxide ($OH^-$).
Practice Quiz
Test your knowledge on Fundamental Particles.
Sir you are doing a great job.
ReplyDelete