Chemistry Essentials
Syllabus focus
Admission chemistry covers atomic structure, the periodic table, chemical bonding, mole concept and stoichiometry, acids-bases-salts, oxidation-reduction, organic functional groups, and basic environmental chemistry.
Core concepts
Know the Bohr model and electronic configuration rules (Aufbau, Pauli, Hund). Periodic trends: atomic radius decreases across a period and increases down a group; electronegativity and ionisation energy follow the opposite pattern. Bonding: ionic between metals and non-metals; covalent between non-metals; hydrogen bonding explains water's high boiling point. The mole (6.022 × 10²³ particles) links mass, molar mass and volume of gas at STP (22.4 L). Acids donate protons, bases accept them; pH = −log[H⁺]. Oxidation is loss of electrons, reduction is gain; balance redox by the ion-electron method. In organic chemistry, recognise alkanes, alkenes, alkynes, alcohols, aldehydes, ketones, carboxylic acids and esters by their functional groups.
Common traps
Confusing atomic number with mass number; assuming all gases behave ideally at extreme conditions; forgetting that molarity depends on solution volume, not solvent volume; writing unbalanced equations; and mixing up oxidation numbers with valency. In periodic-trend questions, check whether the comparison is along a period or down a group.
Worked example
How many grams of NaOH are needed to make 500 mL of 0.2 M solution? Moles = 0.2 × 0.5 = 0.1 mol. Molar mass of NaOH = 40 g/mol. Mass = 0.1 × 40 = 4 g. Rule of thumb: moles = molarity × volume in litres; then mass = moles × molar mass.
Practice habit
Balance every equation before doing stoichiometry, and always check that units (g, mol, L) are consistent.