Additional -Questions:
Q1. What is atomicity?
Ans: The number of atoms contained in a molecule of a substance is called its atomicity.
Q2. How molecules are categrised on the base of atomicity?
Ans:
1. Monoatomic Molecules (Molecule having 1 atom)
2. Diatomic Molecules (molecule having 2 atoms)
3. Triatomic Molecules (molecules having 3 atoms)
4. Tetraatomic Molecules (molecules having 4 atoms)
5. Ployatomic Molecules (molecules having more than 4 molecules)
1. Atom
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The smallest particle of an element that cannot be divided further by chemical means.
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It retains all the properties of that element.
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Example: H (Hydrogen atom), O (Oxygen atom).
2. Molecule
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A group of two or more atoms (same or different) chemically bonded together.
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Example: H₂ (hydrogen molecule), H₂O (water molecule).
3. Ion
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A charged particle formed when an atom or molecule loses or gains electrons.
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Positive ions → Cations (formed by loss of electrons).
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Negative ions → Anions (formed by gain of electrons).
4. Atomicity
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The number of atoms present in one molecule of an element.
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Example:
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O₂ → Atomicity = 2
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P₄ → Atomicity = 4
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5. Anion
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A negatively charged ion.
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Formed by gain of electrons.
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Example: Cl⁻, O²⁻.
6. Cation
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A positively charged ion.
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Formed by loss of electrons.
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Example: Na⁺, Ca²⁺.
7. One mole atom
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The amount of a substance containing 6.022 × 10²³ atoms of that element.
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Example: 1 mole of carbon = 6.022 × 10²³ atoms of carbon.
8. One mole molecule
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The amount of a substance containing 6.022 × 10²³ molecules.
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Example: 1 mole of water (H₂O) = 6.022 × 10²³ molecules of H₂O.
9. Monoatomic
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A molecule that contains only one atom.
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Example: Noble gases (He, Ne, Ar).
10. Diatomic
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A molecule that contains two atoms.
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Example: H₂, O₂, Cl₂.
11. Triatomic
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A molecule that contains three atoms.
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Example: O₃ (ozone), H₂O (water).
12. Polyatomic
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A molecule that contains more than three atoms.
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Example: P₄ (phosphorus), CH₄ (methane), C₆H₁₂O₆ (glucose).
