Chemistry Notes For Competitive Exams

Atoms: Basic units of matter, composed of protons, neutrons, and electrons. The nucleus contains protons and neutrons, while electrons orbit the nucleus.
Subatomic Particles: Protons (positive charge), neutrons (neutral), and electrons (negative charge).
Atomic Number: Number of protons in the nucleus of an atom, determining the element.
Isotopes: Atoms of the same element with different numbers of neutrons.
Electron Configuration: Distribution of electrons in an atom’s electron shells, important for understanding chemical behavior.

Radioactive Decay: Process by which unstable atomic nuclei lose energy by emitting radiation.
Types of Radiation: Alpha particles (helium nuclei), beta particles (electrons or positrons), and gamma rays (high-energy photons).
Half-Life: Time required for half of the radioactive nuclei in a sample to decay.
Applications: Medical imaging, cancer treatment, radiocarbon dating, nuclear energy.

Ionic Bonding: Transfer of electrons from one atom to another, forming ions. Typically occurs between metals and nonmetals.
Covalent Bonding: Sharing of electrons between atoms, typically between nonmetals.
Metallic Bonding: Sea of electrons shared among a lattice of metal atoms.
Polarity: Distribution of electrical charge over the atoms joined by the bond.
Intermolecular Forces: Forces between molecules, including hydrogen bonding, dipole-dipole interactions, and London dispersion forces.

Periodic Table: Tabular arrangement of elements by increasing atomic number, showing periodic patterns in properties.
Groups and Periods: Columns (groups) and rows (periods) on the periodic table, where elements in the same group have similar chemical properties.
Metals, Nonmetals, and Metalloids: Categories of elements with distinct physical and chemical properties.
Essential Elements: Elements necessary for life, including carbon, hydrogen, oxygen, nitrogen, phosphorus, and sulfur.

Acids: Substances that donate protons (H⁺) in aqueous solutions. Have a pH less than 7.
Bases: Substances that accept protons or donate hydroxide ions (OH⁻) in aqueous solutions. Have a pH greater than 7.
Salts: Compounds formed from the neutralization reaction between an acid and a base.
pH Scale: Measures the acidity or basicity of a solution, ranging from 0 to 14.
Indicators: Substances that change color in response to pH changes, used to identify acidic or basic solutions.

Stoichiometry: Calculation of reactants and products in chemical reactions based on the balanced chemical equation.
Thermochemistry: Study of heat changes that accompany chemical reactions and phase changes.
Electrochemistry: Study of the relationship between electricity and chemical reactions, including redox reactions, galvanic cells, and electrolytic cells.
Organic Chemistry: Study of carbon-containing compounds and their reactions.

Atomic Theory: Concepts about the nature of atoms, including Dalton’s Atomic Theory, Thomson’s Plum Pudding Model, Rutherford’s Nuclear Model, and Bohr’s Model.
Quantum Theory: Describes the behavior of electrons in atoms, incorporating wave-particle duality and the Heisenberg Uncertainty Principle.
Kinetic Molecular Theory: Explains the behavior of gases in terms of the motion of their molecules.
Collision Theory: Describes how chemical reactions occur and why reaction rates vary with conditions, focusing on the collisions between reactant molecules.