Unit 1 Flashcards
Activated complex
The activated complex is a very unstable arrangement of atoms formed at the maximum of the potential energy barrier, during a chemical reaction
Activation energy
The minimum kinetic energy required by colliding particles before the reaction will occur, since a high energy activated complex must be formed
Adsorption
Occurs when molecules become bonded to the surface of a catalyst
Allotrope
One or two or more existing forms of an element. Example: diamond, fullerene and graphite are allotropes of carbon
Bonding electrons
Shared pairs of electrons from both atoms forming the covalent bond
Chemical bonding
The term used to describe the mechanism by which atoms are held together
Chemical structure
Describes the way in which atoms, ions or molecules are arranged
Collision theory
Suggest that for a chemical reaction to occur particles must collide
Covalent bond
Former when 2 atoms share electrons in their outer shell to compel the filling of that shell
Covalent radius
Half the distance between the nuclei of 2 bonded atoms of an element
Delocalised electrons
In metallic bonding, electrons are free from attachment to any one metal ion and are shared amongst the entire structure
Desorption
Occurs when the bonds between the molecules and the surface break and the molecule leave the surface of the catalyst
Diatomic
Molecules with only 2 atoms - oxygen and carbon monoxide
Dipole
An atom or molecule in which a concentration of positive charges is separated from a concentration of negative charge
Electronegativity
A measure of the attraction that an atom involved in a bind has for the electrons of the bond
Enthalpy change
For a reaction is defined as the change in heat energy when 1 mile of reactant is converted to the product(s) at constant pressure
Fullerenes
Molecules of pure carbon constructed from 5- and 6- membered rings combined into hollow structures. The most stable contains 60 carbon atoms in a shape resembling a football
Hydrogen bonds
Electrostatic force of attraction between molecules containing a hydrogen atom bonded to an atom of strongly electronegative element such as fluorine, oxygen or nitrogen and a highly electronegative atom on a neighbouring molecule.
Intermolecular forces
Those which attract molecules together. They are weaker than chemical bonds
Intramolecular forces
Forces of attraction which exist WITHIN a molecule
Ionisation energy
Energy required to remove one mole of electrons from one mole of atoms in the gaseous state
Isoelectronic
Means having the same arrangement of electrons. For example, the noble gas neon, a sodium ion and a magnesium ion are Isoelectronic.
Lattice
Regular 3D arrangement of particles in space. The term is applied to metal ions in a solid, and to positive and negative ions in an ionic solid
London dispersion forces
The forces of attraction which result from the electrostatic attraction between temporary dipoles and induced dipoles caused by movement of electrons in atoms and molecules
Lone pairs
Pairs of electrons in the outer shell of an atom which take no part in bonding
Miscible fluids
Fluids which mix or dissolve in each other in all proportions
Periodicity
The regular recurrence of similar properties when the elements are arranged in order of increasing atomic number
Polar covalent bond
Covalent bond between atoms of different electronegativity, which results in an uneven distribution of electrons and a partial charge along the bond.
Potential energy diagram
Shows the enthalpy of reactants and products, and the enthalpy change during a chemical reaction
Properties of a substance
Their physical and chemical characteristics. These are often a reflection of the chemical bonding and structure of the material
Thermochemical equation
States the enthalpy change for the reaction defined, with reactants and products in the states shown
Viscosity
The resistance to flow that is exhibited by all liquids
