Chemistry terminology consists of scientific terms used to describe chemical substances, properties, reactions, and calculations. Understanding these terms is essential for learning and applying chemistry effectively. 1. Atomic Number (Z) The atomic number is the number of protons present in the nucleus of an atom. It determines the identity of an element. Example: Carbon has an atomic number of 6, meaning it contains 6 protons. 2. Atomic Mass Atomic mass is the average mass of an atom of an element compared to 1/12th the mass of a carbon-12 atom. Example: The atomic mass of oxygen is approximately 16 u. 3. Molecular Mass The sum of the atomic masses of all atoms present in a molecule. Example: H₂O = (2 × 1) + 16 = 18 u 4. Formula Mass The sum of atomic masses of all atoms represented in a chemical formula, especially for ionic compounds. Example: NaCl = 23 + 35.5 = 58.5 u 5. Mole A mole is the amount of substance containing particles (Avogadro's number). Example: 1 mole of water contains water molecules. 6. Molarity (M) Molarity is the number of moles of solute dissolved in one liter of solution. Example: A solution containing 1 mole of NaCl in 1 liter of solution has a molarity of 1 M. 7. Molality (m) Molality is the number of moles of solute dissolved in one kilogram of solvent. Example: A solution containing 1 mole of glucose in 1 kg of water has a molality of 1 m. 8. Oxidation Oxidation is the loss of electrons by an atom, ion, or molecule. It is often associated with an increase in oxidation number. Example: Fe → Fe²⁺ + 2e⁻ Iron loses electrons and is oxidized. 9. Reduction Reduction is the gain of electrons by an atom, ion, or molecule. It is often associated with a decrease in oxidation number. Example: Cu²⁺ + 2e⁻ → Cu Copper ion gains electrons and is reduced. 10. Oxidizing Agent A substance that causes oxidation of another substance and itself gets reduced. Example: Oxygen (O₂), KMnO₄. 11. Reducing Agent A substance that causes reduction of another substance and itself gets oxidized. Example: Hydrogen (H₂), Carbon monoxide (CO). 12. Endothermic Reaction A chemical reaction that absorbs heat energy from its surroundings. Characteristics: Surroundings become cooler. Energy is absorbed. Example: Photosynthesis, thermal decomposition of calcium carbonate. 13. Exothermic Reaction A chemical reaction that releases heat energy to its surroundings. Characteristics: Surroundings become warmer. Energy is released. Example: Combustion of fuel, neutralization reactions. 14. Catalyst A substance that increases the rate of a chemical reaction without being consumed. Example: Manganese dioxide (MnO₂) in the decomposition of hydrogen peroxide. 15. pH A measure of the acidity or basicity of a solution. pH < 7 = Acidic pH = 7 = Neutral pH > 7 = Basic Example: Lemon juice has a pH around 2, while soap solution has a pH around 10. 16. Electrolyte A substance that conducts electricity when dissolved in water or in molten form. Example: NaCl solution, HCl solution. 17. Isotope Atoms of the same element having the same atomic number but different mass numbers. Example: Carbon-12, Carbon-13, Carbon-14. 18. Chemical Equilibrium A state in which the rates of forward and reverse reactions become equal. Example: N₂ + 3H₂ ⇌ 2NH₃ 19. Saturated Solution A solution that contains the maximum amount of solute that can dissolve at a given temperature. Example: Sugar solution containing no more dissolved sugar at room temperature. 20. Unsaturated Solution A solution that can dissolve more solute at a given temperature. Example: Dilute salt solution. 👉 Follow for more easy content! or join our Whatsapp channel👇👇👇👇 https://whatsapp.com/channel/0029Vb7uiP0AYlUNkzs66y0o #Aspire_Coaching_Academy #Malakand #chemistrynotes #chemistry #1MillionViewsOnMyFirstVideo - @aspire.coaching.a