Chemistry — SSC CGL Study Notes

Overview

Chemistry questions in SSC CGL Tier 1 typically constitute 4–6 marks out of the 25-mark General Science section. The exam tests foundational concepts from three areas: the periodic table and atomic structure, acid-base chemistry and pH, and basic organic chemistry including hydrocarbons and functional groups. Unlike board exams that require detailed derivations, SSC focuses on fact recall, simple applications, and real-world connections—think everyday chemicals, common reactions, and properties you can observe.

Success in this section requires memorizing key facts (atomic numbers, pH values, functional groups) and understanding simple cause-effect relationships (why metals react with acids, what makes a compound acidic). Questions are usually direct: "What is the pH of blood?" or "Which element has atomic number 26?" Occasionally you'll see application-based questions linking chemistry to daily life (bleaching powder composition, uses of common acids). The syllabus is broad but shallow—prioritize high-frequency topics and practice previous year questions to identify patterns.

Key Concepts

• **Periodic Table Organization**: Elements are arranged by increasing atomic number in 18 groups (vertical columns) and 7 periods (horizontal rows). Groups contain elements with similar chemical properties because they have the same number of valence electrons.

• **Metals, Non-metals, Metalloids**: Metals (left and center) are malleable, ductile, good conductors, and form positive ions. Non-metals (right side) are brittle, poor conductors, and form negative ions. Metalloids (B, Si, Ge, As, Sb, Te) show intermediate properties.

• **Acids and Bases**: Acids release H⁺ ions in water (HCl, H₂SO₄, HNO₃), taste sour, turn blue litmus red. Bases release OH⁻ ions (NaOH, Ca(OH)₂), taste bitter, feel slippery, turn red litmus blue. pH scale runs 0–14: below 7 is acidic, 7 is neutral, above 7 is basic.

• **Salt Formation**: Acid + Base → Salt + Water (neutralization). The salt's nature depends on the strength of the parent acid and base. Strong acid + strong base = neutral salt (NaCl). Weak acid + strong base = basic salt (sodium acetate).

• **Organic Chemistry Basics**: Organic compounds contain carbon-hydrogen bonds. Hydrocarbons are pure C-H compounds: alkanes (single bonds, C_nH_{2n+2}), alkenes (double bonds, C_nH_{2n}), alkynes (triple bonds, C_nH_{2n-2}).

• **Functional Groups**: An atom or group that determines a compound's chemical behavior. Common ones: –OH (alcohol), –COOH (carboxylic acid), –CHO (aldehyde), –CO– (ketone), –NH₂ (amine).

• **Valency and Chemical Bonding**: Valency is the combining capacity of an element (H=1, O=2, N=3, C=4). Ionic bonds form by electron transfer (NaCl), covalent bonds by electron sharing (H₂O, CO₂).