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Table of Definitions

A-F| G-L| M-R| S-Z| Other pages

A-F

Acid: Proton donor (Bronsted-Lowry definition).
Acid Dissociation Constant (Ka): The equilibrium constant for the dissociation of an acid in aqueous solution.
Activation Energy: The minimum energy required for a molecular collision to result in a reaction.
Addition (Reaction): When two or more molecules join to make one.
Aliphatic: Not aromatic.
Aromatic: Refers to compounds that have unsaturated cyclic molecules with delocalized electrons.
Atom: Smallest particle unique to an element.
Average Bond Energy: The average energy required to break one mole of a particular kind of bond, taken from many compounds. (It is also called average bond enthalpy).
Avogadro's Number: The number of atoms in exactly 12 grams of carbon-12.
Base: Proton acceptor.
Bond Energy: The energy required to break one mole of a particular kind of bond in a particular compound.
Catalyst: A substance that changes the rate of reaction without altering itself. (including not being used up)
Complex: A central atom or ion surrounded by a cluster of molecules or ions called ligands. The ligands are attached by dative covalent bonds. (D-block elements)
Coordination Number: Number of atoms or ions around a particular atom or ion.
Condensation Reaction: When two or more molecules join with the formation of a small molecule.
Conjugate Acid: The acid formed when a base accept a proton.
Conjugated Base: The base formed when an acid donates a proton.
Covalent Bonding: Strong forces of attraction between oppositely charged ions in an ionic lattice.
Dative Covalent Bond: A covalent bond where both electrons come from the same atom.
Dipole-Dipole Attraction: Attraction between molecules that have permanent dipoles.
Disproportionation: Simultaneous oxidation and reduction of the same element in a reaction.
Distribution Law: A solution will distribute itself between a pair of immiscible solvents in a constant ratio of concentrations (known as the partition of distribution coefficient) at constant temperature, and provided there is insufficient solute to saturate either of the solvents.
Dynamic Equilibrium: When the concentrations/ amounts of reactants and products are constant but the forward and reverse processes are still occurring (at equal rates).
Electrode Potential: The potential difference between an electrode and the solution that it dips into.
Electronegativity: A measure of the attractiveness of an atom (NOT ions or molecules) for electrons.
Electrophile: A molecule or ion with an electron deficient site which can accept a pair of electrons.
Elimination Reaction: When a molecule loses a small molecule and the degree of unsaturation increases.
Empirical Formula: Simplest ratio of atoms of the different elements in a compound.
Enthalpy Change: An energy change that occurs at constant pressure.
Entropy: A measure of disorder.
Equilibrium law: At equilibrium there is a simple relationship between the concentrations of reactants and products.
Free Radical: Particle with an unpaired electron
1st Electron Affinity: The energy released when one mole of an ionic solid is formed from its constituent gaseous ions.
1st Ionization Energy: The energy required to remove one mole of electrons from one mole of gaseous atoms to form one mole of ions with a single positive charge.
Electrode Potential: The potential difference between an electrode and the solution that it dips into.

G-L

Geometric Isomers: Stereoisomers where a pair of atoms (or groups) are on the same or opposite sides of a molecule.
Group: Vertical column of elements in the periodic table. Elements in the same group have similar properties because the atom have the same number of electrons in the same type(s).
Hess' Law: The energy change accompanying a process is independent of the route taken.
Heterolitic Catalyst: A catalyst that is in a different phase to the reaction.
Heterolitic Fission: When a covalent bond breaks such that both electrons go to the same atom.
Homolitic Fission: When a covalent bond breaks such that each bonded atom receives one electron.
Homogeneous Catalyst: A catalyst that is in the same phase as the reaction.
Hydrogen Bonding: A weak force of attraction between an electron deficient hydrogen atom (usually covalent bond to a N, O, or F atom) and the lone pair on a N, O , or F atom.
Ion: Atom or group of atoms with an electronic charge.
Ionic Bonding: Strong forces of attraction between oppositely charged ions in an ionic lattice.
Isotopes: Atoms of the same element (or atomic number) with different mass number (or number of neutrons).
Isomers: Different compounds with the same molecular formula.
Lattice Energy: The energy released when one mole of an ionic solid is formed from its constituent gaseous ions.

M-R

Metallic Bonding: Strong forces of attraction between cation and the sea of electrons in which they are embeded.
Molecular Formula: The actual number of each kind of atom in a molecule of the compound.
Mole: Amount of substance that contains Avogadro's number of particles.
Molecule: Group of atoms held together by covalent bonds (there are two types: simple molecule and giant molecule).
Molecularity: The number of molecules in the rate determining step.
Nucleophile: A molecule or ion with an electron rich site which can donate a pair of electrons.
Order of a electron: Sum of the powers in the rate expression.
Oxidation: Gain of oxygen/ Loss of electrons/ Loss of hydrogens
Period: Horizontal row of elements in the periodic table.
Periodicity: The way the properties of the elements, when they are arranged in order of increasing atomic number, show a repeated pattern.
Rate Constant: The constant of proportionality in the rate expression.
Rate Determining Step: The slowest step in the mechanism of a reaction.
Reduction: Loss of oxygen/ Gain of electron/ Gain of hydrogen.
Relative Isotopic Mass: Mass of an isotope divided by 1/12 of the mass of an atom of the carbon 12.
Relative Atomic Mass: The weighted average mass of an atom of an element divided by 1/12 of the mass of an atom of the carbon 12.
Relative Molecular Mass: The weighted average mass of a molecule of a substance divided by 1/12 of the mass of an atom of the carbon 12.
Rr Value (Chromatography): The ratio of distance moved by substance to distance moved by solvent front.

S-Z

Standard Condition: 25C (298k)/ 1 atmosphere pressure/ 1mole of concentration
Standard Electrode Potential: The potential difference between a half cell and the standard hydrogen electrode, when no current flows, under standard condition.
Stereo Isomers: They have the same structural formula but different arrangements of atoms in space.
Structural Formula: Formulas that show the arrangement of atoms.
Structural Isomers: They have the same molecular mole, but different structures.
Substitution (reaction): When an atom or group is replaced by another atom or group.
The Ionic Product of Water (Kw): The equilibrium constant for the dissociation of water.
Transition Element: An element that forms at least one ion with a particularly filled d subshell.
Vander Waals' Forces: Weak attraction between a temporary dipole in one molecule and the induced dipole in an adjacent molecule.

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Structure and Bonding