chemistry defs

• temperature of gas def


  the temperature of a gas is directly proportional to the average kinetic energy of the particles of the gas
• orbital

  an orbital is a three dimensional region around the nucleus where there is a high probability of finding an electron with a certain amount of energy
• isotopes

  isotopes are different atoms of the same element with the same atomic number but different mass numbers
• relative atomic mass


  the relative atomic mass (Ar) is a number that compares the average mass of an atom with the mass of the C-12 atom taken to be 12 units
• ionisation energy


  the ionisation energy is the minimum amount of energy required to remove an electron from an atom in the gas phase
• chemical bonding


  chemical bonding is the process by which atoms bond with each other and in this way achieve a noble gas configuration, with low potential energy
• molecule


  a molecule is a group of two or more atoms which are bonded together strongly enough to behave as a single unit in a chemical reaction
• bond strength


  bond strength is the amount of energy needed to break a chemical bond
• valency


  Valency is a measure of the number of chemical bonds formed by the atoms of a given element
• covalent bond


  a covalent bond involves the sharing of at least one pair of electrons by two atoms
• Intramolecular bond 


  bond which occurs between atoms within a molecule
• Electronegativity 


  A measure of the tendency of an atom to attract a bonding pair of electrons
• Non polar covalent bond

  A bond where there is equal sharing of electrons due to there being a zero difference in electronegativity
• Polar covalent bond 


  A bond where there is unequal sharing of electrons due to there being a difference in electronegativity
• Dipole


  Separation of charge between 2 covalentply bonded atoms
• intermolecular forces 


  An intermolecular force is a force of attraction between molecules or

  between atoms of noble gases
• london force

  London forces exist between two non-polar molecules or between atoms of Noble gases.
• dipole-dipole


  the force of attraction between the positive end of one polar molecule and the negative end of another polar molecule.
• hydrogen bonding

  Hydrogen bonding results from the attractive force between polar molecules in which a

  hydrogen atom is covalently bonded to either N, O, or F due to these being:

  • Small atoms

  • Of high electronegativity

  • with at least one lone pair of electrons
• ionic bonding

  An ionic bond forms due to a transfer of electrons to form

  cations and anions which are electrostatically attracted in an

  ionic lattice.
• crystal lattice 


  A crystal lattice is a regular three-dimensional structure of particles.
• metallic bond 


  A metallic bond is the attraction between positive kernels and a sea of

  delocalised electrons.
• allotropes

  Allotropes are different forms of the same element.