Ideal Gas
An ideal gas is a theoretical gas composed of randomly moving point particles that undergo perfectly elastic collisions and experience no intermolecular forces. The behavior of an …
Chemical Glossary — Letter I
62 chemicals found starting with "I"
Ideal Gas Law
The equation of state for an ideal gas: PV = nRT, where P is pressure, V is volume, n is moles, R is the gas constant (8.314 J/mol·K), and T is absolute temperature. Real gases app…
Ideal Solution
A solution that obeys Raoult's law over all compositions and concentrations. In an ideal solution, solute-solvent interactions are equal to solvent-solvent and solute-solute intera…
Ideal Solution
An ideal solution is a solution that obeys Raoult's law exactly at all concentrations; the interactions between solute and solvent molecules are identical to those between the pure…
Indicator
A substance that changes color depending on the pH of a solution, used to signal the end point in acid-base titrations. Common indicators include litmus (red in acid, blue in base)…
Indicators
Chemical indicators are substances that change color in response to changes in the chemical environment, most commonly pH, making them useful for detecting the equivalence point in…
Indium
Indium is a soft, silvery-white post-transition metal, atomic number 49. Emits a high-pitched squeal when bent (indium cry). Critical material for thin-film solar cells (CIGS) and …
Induced Dipole
A temporary dipole created in a nonpolar molecule by a nearby polar molecule or ion. The electric field of the polar species distorts the electron cloud of the nonpolar molecule. I…
Inert Gas
An inert gas is a gas that does not undergo chemical reactions under normal conditions. In the strictest sense, this refers to the noble gases (Group 18: He, Ne, Ar, Kr, Xe, Rn) be…
Inert S Pair Effect
The inert s-pair effect refers to the tendency of the two electrons in the outermost s-orbital of heavier p-block elements (e.g., lead, thallium, tin) to remain in a non-bonding st…
Infrared Spectroscopy
A technique that measures the absorption of infrared radiation by molecules, causing vibrational and rotational transitions. Different functional groups absorb at characteristic fr…
Inhibition
The reduction of a chemical reaction rate or enzymatic activity by an inhibitor molecule. Competitive inhibition involves molecules binding to the active site; non-competitive inhi…
Inhibitor
A substance that decreases the rate of a chemical reaction. Enzyme inhibitors reduce enzymatic activity by binding to the active site (competitive) or elsewhere on the enzyme (non-…
Inhibitory Catalyst
An inhibitory catalyst (or inhibitor) is a substance that decreases the rate of a chemical reaction by interfering with the catalytic mechanism, often by binding to the active site…
Inner Orbital Complex
An inner orbital complex is a coordination compound in which the ligands cause hybridization that uses inner d-orbitals (n-1)d in addition to the ns and np orbitals of the central …
Inner Transition Elements
Inner transition elements are the elements in which the last electron enters the f-orbital (f-block elements). They are placed in two rows at the bottom of the periodic table: the …
Inorganic Chemistry
The branch of chemistry concerned with the properties, reactions, and synthesis of inorganic compounds — those not based on carbon-carbon or carbon-hydrogen bonds. It encompasses t…
Insoluble Compound
An insoluble compound is a substance that does not dissolve appreciably in a given solvent, typically water, under standard conditions. In practice, insolubility is a relative term…
Insulator
An electrical insulator is a material that strongly resists the flow of electric current due to the absence of free charge carriers, typically having a large band gap between the v…
Integrated Rate Equation
The integrated rate equation expresses the concentration of a reactant as a function of time for a given reaction order, derived by integrating the differential rate law. For a fir…
Intensive Property
An intensive property is a physical or chemical property of a substance that does not depend on the amount or size of the sample. Intensive properties are the same whether you have…
Intermediate
A species formed during a reaction mechanism that is consumed in a subsequent step and does not appear in the overall balanced equation. Intermediates have finite lifetimes and exi…
Intermolecular Forces
Attractive and repulsive forces between molecules that determine physical properties like boiling point, viscosity, and surface tension. Types include London dispersion forces, dip…
Intermolecular Forces
Intermolecular forces are the attractive and repulsive forces between molecules that determine physical properties such as boiling point, viscosity, and surface tension. They inclu…
Interstitial
In chemistry and materials science, interstitial refers to atoms, ions, or molecules that occupy the spaces (interstices) between the atoms in a crystal lattice. Interstitial sites…
Intramolecular Forces
Forces that hold atoms together within a molecule, including covalent bonds, ionic bonds, and metallic bonds. Intramolecular forces are generally much stronger than intermolecular …
Iodine
Iodine is a lustrous purple-black non-metal halogen, atomic number 53. Sublimates readily to give a distinctive violet vapour. Essential trace element for thyroid hormone (thyroxin…
Iodine Test
A chemical test for starch using iodine solution (iodine in potassium iodide). Starch turns dark blue-black in the presence of iodine due to starch molecules forming a complex with…
Ion
An atom or molecule that has gained or lost one or more electrons, acquiring a net electric charge. Cations (positive ions) have lost electrons; anions (negative ions) have gained …
Ion
An ion is an atom or molecule that has gained or lost one or more electrons, giving it a net positive or negative electric charge. Positively charged ions are called cations; negat…
Ion Exchange
A process in which ions in solution are exchanged with ions of the same charge bound to an ion exchange resin. Used in water softening (replacing Ca²⁺ and Mg²⁺ with Na⁺), deionizat…
Ion Product
The ion product (Q) is the reaction quotient applied specifically to ionic reactions, calculated from the actual concentrations of ions at any given moment (not necessarily at equi…
Ion Product For Water
The ion product for water (Kw) is the equilibrium constant for the autoionization of water: 2H₂O ⇌ H₃O⁺ + OH⁻, expressed as Kw = [H₃O⁺][OH⁻]. At 25°C, Kw = 1.0 × 10⁻¹⁴, which defin…
Ion-Dipole Force
An attractive intermolecular force between an ion and a polar molecule. Ion-dipole forces are stronger than dipole-dipole forces and are responsible for the solvation of ions in po…
Ionic Bond
A chemical bond formed by the electrostatic attraction between oppositely charged ions (cation and anion). Formed when a metal transfers electrons to a nonmetal. Ionic compounds ha…
Ionic Bonding
Ionic bonding is a type of chemical bond formed by the electrostatic attraction between oppositely charged ions, typically a metal cation and a nonmetal anion. It arises when elect…
Ionic Compounds
Ionic compounds are chemical compounds composed of positively and negatively charged ions held together by electrostatic forces in a crystalline lattice structure. They are general…
Ionic Equation
A chemical equation that shows dissolved ionic compounds as separate ions rather than as neutral formula units. In a net ionic equation, spectator ions (ions unchanged in the react…
Ionic Geometry
Ionic geometry refers to the three-dimensional arrangement of ions in an ionic crystal lattice, determined by the relative sizes of the cations and anions (radius ratio) and the re…
Ionic Product of Water
The equilibrium constant for the autoionization of water: Kw = [H⁺][OH⁻] = 1.0 × 10⁻¹⁴ at 25°C. This relationship links [H⁺] and [OH⁻] concentrations in any aqueous solution and is…
Ionisation Energy
The energy required to remove an electron from a gaseous atom or ion to form a positive ion. First ionisation energy is the energy to remove the outermost electron from a neutral a…
Ionization
Ionization is the process by which an atom or molecule acquires a positive or negative charge by gaining or losing electrons, forming ions. It can occur through various means inclu…
Ionization
Ionization is the process by which an atom, molecule, or ion gains or loses electrons to become an electrically charged species (an ion). The energy required to remove the outermos…
Ionization Constant
The ionization constant (Ka for acids, Kb for bases) is the equilibrium constant for the ionization of a weak acid or base in water. For a weak acid HA, Ka = [H⁺][A⁻]/[HA], measuri…
Ionization Energy
Ionization energy is the minimum energy required to remove the most loosely bound electron from a gaseous atom or ion in its ground state. First ionization energy refers to the rem…
Ionization Isomers
Ionization isomers are coordination compounds that have the same molecular formula but differ in the ligand coordinated to the central metal atom versus the counter-ion present out…
Iridium
Iridium is a hard, brittle, silvery-white platinum group metal, atomic number 77. The most corrosion-resistant metal known. Second densest element after osmium. The Cretaceous-Pale…
Iron
Iron is a lustrous, silver-grey transition metal, atomic number 26. The most used metal in the world - primarily as steel. Fourth most abundant element in Earth crust. Essential fo…
Irreversible Reaction
An irreversible reaction is a chemical reaction that proceeds in only one direction and goes to completion, converting essentially all reactants to products. The reverse reaction i…
Isobaric
Isobaric refers to a process or transformation that occurs at constant pressure. Most chemical reactions and phase changes conducted in open containers are isobaric because atmosph…
Isochoric
Isochoric refers to a process or transformation that occurs at constant volume. No work of expansion or compression is done in an isochoric process (w = 0, since ΔV = 0). At consta…
Isoelectric
The isoelectric point (pI) is the pH at which a molecule — particularly an amino acid, protein, or other amphoteric species — carries no net electrical charge. At the isoelectric p…
Isoelectronic
Describes atoms, ions, or molecules that have the same number of electrons and the same electronic configuration. For example, N³⁻, O²⁻, F⁻, Ne, Na⁺, Mg²⁺, and Al³⁺ are all isoelec…
Isomer
One of two or more compounds with the same molecular formula but different arrangements of atoms. Structural isomers have different connectivity; stereoisomers (geometric and optic…
Isomerism
The phenomenon where two or more compounds share the same molecular formula but differ in structural arrangement or spatial orientation of atoms. Types include constitutional (stru…
Isomers
Isomers are compounds that have the same molecular formula but different structural arrangements of atoms, resulting in different physical and/or chemical properties. They are broa…
Isomorphous
Isomorphous substances are those that crystallize in the same or very similar crystal structures and have similar chemical formulas, often because they contain ions or atoms of sim…
Isothermal
A process occurring at constant temperature. For an ideal gas, isothermal expansion follows Boyle's law (PV = constant). In thermodynamics, isothermal processes involve heat exchan…
Isotonic
Isotonic solutions are solutions that have the same osmotic pressure as another reference solution. In biology and medicine, isotonic solutions have the same osmotic concentration …
Isotope
Atoms of the same element (same atomic number) that have different numbers of neutrons and thus different mass numbers. Isotopes of an element have nearly identical chemical proper…
Isotopes
Variants of an element that have the same number of protons but different numbers of neutrons. While isotopes of an element behave almost identically chemically, their different ma…
Isotropic
Having the same physical properties in all directions. Liquids and amorphous solids (like glass) are isotropic, while crystalline solids and liquid crystals are often anisotropic (…
About Chemicals Starting With I
This page lists all chemicals in our database beginning with the letter I. 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.