Cadmium
Cadmium is a soft, silvery-white transition metal, atomic number 48. Highly toxic heavy metal and carcinogen. Mainly occurs as a by-product of zinc smelting. Historically used in n…
Chemical Glossary — Letter C
89 chemicals found starting with "C"
Caesium
Caesium is a soft, gold-coloured alkali metal, atomic number 55. Has the lowest ionisation energy and electronegativity of any stable element. The caesium atomic clock defines the …
Calcium
Calcium is a soft, grey alkaline earth metal, atomic number 20. Fifth most abundant element in Earth crust. Essential for life - major component of bones, teeth, shells. Calcium io…
Californium
Californium is a synthetic radioactive actinide and a very strong neutron emitter. It was first produced at the University of California, Berkeley in 1950. It has practical uses as…
Calorie
The calorie (cal) is a unit of energy defined as the heat needed to raise the temperature of 1 gram of water by 1°C at 15°C. The nutritional Calorie (kcal) equals 1000 calories. In…
Calorimeter
A calorimeter is an insulated device used to measure the heat released or absorbed during a chemical reaction, physical change, or combustion. Common types include the coffee-cup c…
Canal Ray
Canal rays (also called anode rays or positive rays) are beams of positive ions produced in a discharge tube by removing electrons from gas atoms. They travel in the opposite direc…
Capillary
A capillary is a very narrow tube, typically with an internal diameter of less than 1 mm, used in chemistry for capillary action, capillary electrophoresis, and melting point deter…
Capillary Action
Capillary action (capillarity) is the spontaneous rise or fall of a liquid in a narrow tube or porous material due to the interplay of adhesive forces (between liquid and tube) and…
Carbanion
A carbanion is a carbon-containing anion in which the carbon bears a negative charge, meaning it has three bonds and an unshared pair of electrons. Carbanions are important reactiv…
Carbon
Carbon is a non-metal, atomic number 6, forming the basis of all known life. Allotropes include diamond, graphite, graphene, and fullerenes. Forms more compounds than any other ele…
Carbonium Ion
A carbonium ion (carbocation) is a positively charged carbon-containing ion in which a carbon atom bears a positive charge and has only three bonds. Carbocations are important reac…
Carcinogen
A carcinogen is a substance, mixture, or radiation that promotes carcinogenesis—the formation of cancer. Chemical carcinogens may act by directly damaging DNA (genotoxic carcinogen…
Catalyst
A catalyst is a substance that increases the rate of a chemical reaction without being consumed in the process, by providing an alternative reaction pathway with a lower activation…
Catenation
Catenation is the ability of atoms of the same element to form long chains or ring structures by bonding with one another. Carbon exhibits catenation to an exceptional degree, form…
Cathode
The cathode is the electrode at which reduction occurs in an electrochemical cell. In an electrolytic cell, the cathode is connected to the negative terminal of the power source, a…
Cathode Ray Tube
A cathode ray tube (CRT) is an evacuated glass tube in which electrons (cathode rays) emitted from a heated cathode are accelerated by an electric field and deflected by electric o…
Cathodic Protection
Cathodic protection is a technique used to prevent corrosion of metal structures by making them the cathode of an electrochemical cell. This is achieved either by connecting the st…
Cation
A cation is a positively charged ion formed when an atom or molecule loses one or more electrons. Cations are attracted to the negatively charged cathode during electrolysis. Metal…
Cell Potential
Cell potential (electromotive force, EMF) is the voltage or electrical potential difference between the cathode and anode of an electrochemical cell. It is measured in volts and re…
Central Atom
The central atom in a molecule or ion is the atom that is bonded to more atoms than any other, forming the core of the molecular structure. In Lewis structures and VSEPR theory, th…
Cerium
Cerium is a soft, silvery, ductile rare earth metal, atomic number 58. Most abundant lanthanide. Pyrophoric as powder or shavings - sparks when struck (used in lighter flints). Cer…
Chain Reaction
A chain reaction is a self-sustaining sequence of reactions in which one of the products or by-products causes subsequent reactions of the same kind. In nuclear chemistry, a chain …
Chain Termination Step
The chain termination step is the final step in a free-radical chain reaction mechanism in which two radicals combine to form a stable non-radical product, ending the chain. Common…
Charles's Law
Charles's Law states that at constant pressure, the volume of a fixed amount of ideal gas is directly proportional to its absolute temperature (V ∝ T, or V/T = constant). First pub…
Chemical Bonds
Chemical bonds are the attractive forces holding atoms together in compounds and molecules. The main types are ionic bonds (electrostatic attraction between oppositely charged ions…
Chemical Change
A chemical change (chemical reaction) is a process that results in the transformation of one or more substances into different substances with new chemical compositions and propert…
Chemical Equation
A chemical equation is a symbolic representation of a chemical reaction showing the reactants on the left and products on the right, separated by an arrow. Balanced chemical equati…
Chemical Equilibrium
Chemical equilibrium is the state in a reversible reaction where the rate of the forward reaction equals the rate of the reverse reaction, so that the concentrations of reactants a…
Chemical Hygiene Officer (CHO)
A Chemical Hygiene Officer (CHO) is a person designated in a laboratory to develop and implement the chemical hygiene plan, ensure compliance with safety regulations, and provide g…
Chemical Hygiene Plan (CHP)
A Chemical Hygiene Plan (CHP) is a written programme required by OSHA for laboratories working with hazardous chemicals. It outlines the specific work practices, procedures, and po…
Chemical Kinetics
Chemical kinetics is the branch of physical chemistry concerned with the rates of chemical reactions and the factors that influence them, including concentration, temperature, cata…
Chemical Periodicity
Chemical periodicity refers to the recurring trends in chemical properties of elements as atomic number increases across the periodic table. Periodic trends include atomic radius, …
Chlorine
Chlorine is a yellow-green diatomic halogen gas, atomic number 17, with pungent suffocating odour. Powerful oxidising agent and disinfectant. Used as chemical warfare agent in WWI.…
Chromium
Chromium is a hard, lustrous transition metal, atomic number 24. Famous for its corrosion resistance and bright finish in electroplating. Chromium(III) compounds are relatively saf…
Cis
Cis is a Latin prefix meaning "on the same side", used in chemistry to describe geometric isomers in which identical or similar substituents are on the same side of a double bond o…
Cis-Trans Isomerism
Cis-trans isomerism (geometric isomerism) occurs when atoms or groups cannot rotate freely due to a double bond or ring structure, resulting in compounds with the same molecular fo…
Clay
Clay is a naturally occurring fine-grained mineral material composed mainly of phyllosilicate minerals with layered structures. Clays are important in chemistry as ion-exchange mat…
Cloud Chamber
A cloud chamber is a particle detector consisting of a sealed container with a supersaturated vapour of water or alcohol. When charged particles (such as alpha or beta particles) p…
Cobalt
Cobalt is a hard, lustrous, silver-grey transition metal, atomic number 27. Used since antiquity to produce blue colour in glass and ceramics (cobalt blue). Essential trace element…
Coefficient of Expansion
The coefficient of thermal expansion is a measure of how much a material expands per degree of temperature increase. For gases, the volume coefficient of expansion at constant pres…
Cohesive Forces
Cohesive forces are the intermolecular attractive forces between like molecules in a substance. These forces are responsible for surface tension and the tendency of liquids to mini…
Coke
Coke is a solid carbonaceous material produced by the destructive distillation (coking) of coal in the absence of air. It consists mainly of carbon with small amounts of hydrogen, …
Colligative Properties
Colligative properties are properties of solutions that depend on the number of solute particles (molecules or ions) rather than on the nature of the solute. The four main colligat…
Collision Theory
Collision theory explains chemical reaction rates by proposing that reactions occur only when reactant molecules collide with sufficient energy (greater than or equal to the activa…
Colloid
A colloid (colloidal dispersion) is a mixture in which particles of one substance (1–1000 nm in size) are dispersed throughout another but not dissolved. Colloids differ from true …
Combination Reaction
A combination reaction (synthesis reaction) is a reaction in which two or more substances combine to form a single product. The general form is A + B → AB. Examples include iron re…
Combustible
A combustible substance is one capable of burning in oxygen to produce heat and light. In regulatory contexts, combustible liquids typically have flash points above 37.8°C (100°F),…
Common Ion Effect
The common ion effect is the decrease in solubility of a sparingly soluble salt when a solution already containing one of its ions is added. For example, the solubility of AgCl dec…
Complex Ions
Complex ions (coordination ions) consist of a central metal ion bonded to a number of ligands (molecules or anions with lone pairs) through coordinate (dative) covalent bonds. The …
Composition Stoichiometry
Composition stoichiometry involves calculating the quantitative relationships between elements in a compound, expressed as percentages by mass or mole ratios. It uses the chemical …
Compound
A compound is a pure substance consisting of two or more different elements chemically bonded together in a fixed ratio by mass. Compounds have properties different from their cons…
Compressed Gas
A compressed gas is any gas stored under pressure in a cylinder or container. Compressed gases include oxygen, nitrogen, hydrogen, acetylene, and carbon dioxide cylinders used in l…
Concentration
Concentration is the amount of solute dissolved in a given volume or mass of solvent or solution. Common units include molarity (mol/L), molality (mol/kg), mass percent (%), and pa…
Condensation
In chemistry, condensation refers to two related phenomena: (1) a phase change in which a vapour converts to a liquid by releasing heat, and (2) a condensation reaction (condensati…
Condensed Phases
Condensed phases are the solid and liquid states of matter, as distinct from the gaseous state. In condensed phases, particles are in close contact and intermolecular forces are si…
Condensed States
Condensed states refer to the solid and liquid phases of matter in which atoms or molecules are closely packed together, in contrast to the vapour phase. The term is often used int…
Conduction Band
The conduction band is the range of electron energies in a solid at which electrons can move freely and conduct electricity. In conductors (metals), the conduction band overlaps wi…
Conformations
Conformations are the different three-dimensional arrangements of atoms in a molecule that arise from rotation about single bonds, without breaking any bonds. In cyclohexane, the m…
Conjugate Acid-Base Pair
A conjugate acid-base pair consists of two species related by the gain or loss of a single proton (H⁺). The conjugate base is formed when an acid loses a proton; the conjugate acid…
Conjugated Double Bonds
Conjugated double bonds are alternating single and double bonds in a molecule, creating a system of overlapping p orbitals in which pi electrons are delocalised across multiple ato…
Contact Process
The Contact Process is the industrial method for manufacturing sulfuric acid (H₂SO₄). It involves: (1) burning sulfur or roasting metal sulfides to form SO₂, (2) catalytic oxidatio…
Continuous Spectrum
A continuous spectrum contains all wavelengths of electromagnetic radiation within a range, appearing as a rainbow of colours with no gaps. It is produced by hot dense objects (sol…
Control Rods
Control rods are neutron-absorbing rods inserted into a nuclear reactor to regulate the rate of the fission chain reaction. Made of materials with high neutron-absorption cross-sec…
Coordinate Covalent Bond
A coordinate covalent bond (dative bond) is a covalent bond in which both electrons in the shared pair are donated by the same atom, called the donor. The atom accepting the electr…
Coordination Compound or Complex
A coordination compound (or complex) consists of a central atom or ion (usually a transition metal) surrounded by a set of ligands bonded to it through coordinate covalent bonds. T…
Coordination Isomers
Coordination isomers are isomers of coordination compounds in which the ligands are distributed differently between the cationic and anionic parts of the coordination complex. For …
Coordination Number
The coordination number in a coordination compound is the number of donor atoms (from ligands) directly bonded to the central metal ion. Common coordination numbers are 2 (linear),…
Coordination Sphere
The coordination sphere of a complex consists of the central metal atom or ion together with all ligands directly bonded to it. It is usually enclosed in square brackets in the for…
Copernicium
Copernicium is a synthetic radioactive transactinide element named after Nicolaus Copernicus. It may be a gas at room temperature due to relativistic effects. First synthesised in …
Copper
Copper (Cu, atomic number 29) is a soft, malleable, ductile metal with high electrical and thermal conductivity. It was one of the first metals used by humans. Copper forms +1 (cup…
Copper
Copper is a ductile, malleable transition metal with excellent electrical and thermal conductivity. One of the few naturally occurring metallic elements, copper has been used by hu…
Corrosion
Corrosion is the gradual destruction of a material (usually a metal) by chemical reaction with its environment, particularly oxidation by oxygen and moisture. The most familiar exa…
Coulomb
The coulomb (C) is the SI unit of electric charge, equal to the charge transported by a current of one ampere in one second. In Faraday's laws of electrolysis, one faraday (96,485 …
Coulometry
Coulometry is an electroanalytical method that measures the quantity of charge (in coulombs) required to completely convert an analyte from one oxidation state to another. Using Fa…
Covalent Bond
A covalent bond is a chemical bond formed by the sharing of one or more pairs of electrons between two atoms, typically between non-metal atoms. Single bonds share one pair, double…
Covalent Compounds
Covalent compounds are substances whose atoms are held together by covalent bonds rather than ionic bonds. They consist of discrete molecules (molecular compounds) or extended cova…
Critical Mass
Critical mass is the minimum mass of fissile material (such as uranium-235 or plutonium-239) needed to sustain a self-propagating nuclear chain reaction. If the mass is below criti…
Critical Point
The critical point of a substance is the temperature and pressure above which the distinction between liquid and vapour phases disappears, forming a supercritical fluid. At the cri…
Critical Pressure
Critical pressure is the minimum pressure required to liquefy a gas at its critical temperature. Above the critical temperature, no amount of pressure can liquefy the gas. Critical…
Critical Temperature
Critical temperature is the temperature above which a gas cannot be liquefied by applying pressure alone, regardless of how high the pressure is. Below the critical temperature, su…
Crystal Field Stabilization Energy
Crystal Field Stabilization Energy (CFSE) is the stabilisation energy gained by a transition metal complex due to the splitting of d orbitals in a crystal field (ligand field). Ele…
Crystal Field Theory
Crystal Field Theory (CFT) is a model that describes the electronic structure of transition metal complexes by considering the effect of a surrounding array of negative charges (li…
Crystal Lattice
A crystal lattice is the regular, three-dimensional arrangement of atoms, ions, or molecules in a crystalline solid. Lattice points represent the positions of particles and are des…
Crystal Lattice Energy
Crystal lattice energy (lattice enthalpy) is the energy released when one mole of a crystalline ionic compound is formed from its gaseous ions at infinite separation, or equivalent…
Crystalline Solid
A crystalline solid is a solid in which the particles (atoms, ions, or molecules) are arranged in a highly ordered, repeating three-dimensional pattern called a crystal lattice. Cr…
Curie (Ci)
The curie (Ci) is a non-SI unit of radioactivity, defined as the amount of a radioactive substance that undergoes 3.7 × 10¹⁰ disintegrations per second (the activity of 1 gram of r…
Curium
Curium is a transuranic radioactive actinide named in honour of Pierre and Marie Curie. It was the third transuranic element to be discovered. Curium-244 is used as an alpha-partic…
Cyclotron
A cyclotron is a type of circular particle accelerator in which charged particles are accelerated using alternating electric fields and kept on a spiral path by a static magnetic f…
About Chemicals Starting With C
This page lists all chemicals in our database beginning with the letter C. Each entry provides the chemical formula, CAS registry number, physical and chemical properties, common uses, and safety information. Use the alphabetical navigation above to browse other letters, or use the search function to find a specific chemical quickly.
Our chemical glossary covers acids, bases, salts, organic compounds, inorganic compounds, solvents, and many more categories. Click on any chemical name to view its full detailed profile.