Chemistry Notes PDF

**Atoms and Their Structure** - **Subatomic Particles**: - **Protons**: Positive charge, found in the nucleus. - **Neutrons**: No charge, also in the nucleus. - **Electrons**: Negative charge, orbit the nucleus in shells. - **Atomic Number**: Number of protons in an atom, unique for each...

**Atoms and Their Structure** - **Subatomic Particles**: - **Protons**: Positive charge, found in the nucleus. - **Neutrons**: No charge, also in the nucleus. - **Electrons**: Negative charge, orbit the nucleus in shells. - **Atomic Number**: Number of protons in an atom, unique for each element. - **Mass Number**: Total number of protons and neutrons. --- ### **Elements** - There are over 100 known elements. - **Metals**: Found on the left and center of the Periodic Table. - **Non-Metals**: Found on the right side. - **Metalloids**: Have properties of both metals and non-metals (e.g., Silicon). --- ### **Discovering the Elements** - Scientists used properties like reactivity, state, and atomic weights to identify elements. - Mendeleev left gaps in his Periodic Table for elements yet to be discovered and predicted their properties accurately. --- ### **Organising the Elements** - Elements are arranged by their: - **Atomic Number**: Increases from left to right. - **Chemical Properties**: Elements in the same group behave similarly. - **Electron Configuration**: Determines the element’s position. --- ### **Properties of Metals and Non-Metals** - Metals form **basic oxides**, while non-metals form **acidic oxides**. - Metals lose electrons to form **cations**, and non-metals gain electrons to form **anions**. --- ### **Compounds** - **Properties of Compounds**: Differ from their constituent elements. For example: - Sodium (a reactive metal) + Chlorine (a toxic gas) = Sodium Chloride (table salt). - **Formation**: Involves chemical reactions that cannot be reversed easily. --- ### **Making a Compound** 1. **Direct Combination**: Elements react directly (e.g., Fe + S → FeS). 2. **Reaction with Water**: Some elements react with water to form compounds (e.g., Na + H₂O → NaOH + H₂). 3. **Decomposition**: Breaking down compounds into simpler substances (e.g., Electrolysis of water: 2H₂O → 2H₂ + O₂). --- ### **Naming Compounds** 1. **Binary Compounds** (two elements): Name the first element, add the second with "-ide" (e.g., MgO = Magnesium Oxide). 2. **Ternary Compounds** (three elements): Usually include polyatomic ions (e.g., Na₂SO₄ = Sodium Sulfate). --- ### **Common Compounds** - **Oxides**: Metals form basic oxides (e.g., MgO), non-metals form acidic oxides (e.g., CO₂). - **Hydroxides**: Bases like NaOH, which neutralize acids. - **Sulfates**: Found in minerals, used in fertilizers (e.g., CaSO₄). - **Carbonates**: React with acids to release CO₂ (e.g., Na₂CO₃). - **Chlorides**: Salts formed with chlorine (e.g., KCl). --- ### **Mixtures** - **Heterogeneous Mixtures**: Components are visible (e.g., sand and iron filings). - **Homogeneous Mixtures**: Components are uniformly distributed (e.g., sugar in water). --- ### **Methods of Separating Mixtures** 1. **Filtration**: Separates insoluble solids from liquids. 2. **Decanting**: Carefully pouring liquid to separate it from sediment. 3. **Evaporation**: Removes liquid to leave behind solids. 4. **Simple Distillation**: Separates substances with large boiling point differences. 5. **Fractional Distillation**: Uses a fractionating column to separate closer boiling points (e.g., separating ethanol from water). 6. **Chromatography**: Separates based on solubility and movement through a medium. --- ### **Separating Metals from Ores** - **Ore**: A naturally occurring rock containing a metal. 1. **Roasting**: Heating sulfide ores in air to form oxides. 2. **Reduction with Carbon**: For metals like iron (Fe₂O₃ + C → Fe + CO₂). 3. **Electrolysis**: For reactive metals like aluminum, using electricity to extract the metal. --- --- ### **Chemical Reactions** - **Definition**: A process where substances (reactants) are transformed into new substances (products) with different properties. - **Signs of a Chemical Reaction**: 1. Color change 2. Gas production 3. Temperature change 4. Formation of a precipitate 5. Odor change --- ### **Writing Word Equations** - **Format**: Reactants → Products - Example: Magnesium + Oxygen → Magnesium Oxide - **Key Rules**: 1. Write the names of reactants on the left, products on the right. 2. Use "+" to separate multiple reactants or products. 3. An arrow indicates the direction of the reaction. --- ### **Corrosion Reactions** - **Definition**: The deterioration of materials (usually metals) due to chemical reactions with the environment. - Example: **Rusting** (Iron reacts with oxygen and water): Iron + Water + Oxygen → Hydrated Iron(III) Oxide (Rust) - Prevention: Painting, galvanizing, or using protective coatings. --- ### **Using Reactions to Identify Chemicals** - **Tests for Common Gases**: 1. **Hydrogen**: Burns with a "pop" sound. 2. **Oxygen**: Relights a glowing splint. 3. **Carbon Dioxide**: Turns limewater milky. 4. **Chlorine**: Bleaches damp litmus paper. --- ### **Atomic Structure** - **Key Components**: 1. **Protons**: Positive charge, in the nucleus. 2. **Neutrons**: No charge, in the nucleus. 3. **Electrons**: Negative charge, orbit the nucleus in energy levels (shells). - **Electron Arrangement**: - First shell: Maximum 2 electrons - Second shell: Maximum 8 electrons - Third shell: Maximum 8 electrons (for the first 20 elements). --- ### **Discovering the Nucleus** - **Rutherford’s Gold Foil Experiment**: - Fired alpha particles at thin gold foil. - Most passed through, but some were deflected. - Conclusion: Atoms have a dense, positively charged nucleus. --- ### **Protons and Electrons** - **Proton Number**: The number of protons in the nucleus, also known as the **atomic number**. - **Electrons**: Equal to the number of protons in a neutral atom. --- ### **Periodic Table** - **Proton Number**: Determines the element's position. - **Groups**: Vertical columns showing similar chemical properties. - **Periods**: Horizontal rows where properties change gradually. --- ### **Nucleon Number** - **Definition**: The total number of protons and neutrons in the nucleus. - Formula: Nucleon Number = Proton Number + Neutron Number --- ### **Isotopes** - **Definition**: Atoms of the same element with the same number of protons but different numbers of neutrons. - Example: - Carbon-12 (6 protons, 6 neutrons) - Carbon-14 (6 protons, 8 neutrons) --- ### **The Group 1 Elements (Alkali Metals)** - **Examples**: Lithium, Sodium, Potassium. - **Properties**: 1. Highly reactive, especially with water. 2. Reactivity increases down the group. 3. Form basic oxides and hydroxides. - Reaction with Water: Alkali Metal + Water → Metal Hydroxide + Hydrogen. --- ### **The Group 2 Elements (Alkaline Earth Metals)** - **Examples**: Magnesium, Calcium. - **Properties**: 1. Less reactive than Group 1. 2. Form oxides and hydroxides that are less soluble than Group 1 hydroxides. - Example Reaction: Calcium + Water → Calcium Hydroxide + Hydrogen. --- ### **The Group 7 Elements (Halogens)** - **Examples**: Fluorine, Chlorine, Bromine, Iodine. - **Properties**: 1. Reactivity decreases down the group. 2. Form salts when combined with metals. - Example Reaction: Chlorine + Sodium → Sodium Chloride. --- ### **Secondary Data – Chlorinating Water** - Chlorine is added to water to kill bacteria and make it safe to drink. - **Reactions**: 1. Chlorine + Water → Hypochlorous Acid + Hydrochloric Acid 2. Hypochlorous Acid is the active disinfectant. --- ### **Periodic Trends** 1. **Atomic Radius**: Decreases across a period, increases down a group. 2. **Ionization Energy**: Increases across a period, decreases down a group. 3. **Reactivity**: - Metals: Increases down the group. - Non-Metals: Decreases down the group. --- ### **Inside Subatomic Particles** - **Protons and Neutrons**: - Made of quarks (up and down quarks). - Held together by the strong nuclear force. - **Electrons**: - Fundamental particles (not made of smaller parts). ---