Leaving Cert Chemistry Definitions
Refers to the separation of a positive and negative charge
States that equal volumes of gases under the same conditions of temperature and pressure contain equal numbers of molecules
Half L ife
The time taken for half the nuclei in any given sample to decay
The spontaneous breaking up of unstable nuclei with the emission of one or more types of radiation
Robert Boyles Law
States that at a constant temperature, the volume of a fixed mass of gas is inversely proportional to its pressure ---> As pressure increases, volume decreases
Combined Gas Law
Gay-Lussac's Law of Combining Volumes
The volumes of reacting gases and volumes of any gaseous products are in the ratio of small whole numbers provided the volumes are measured at the same temperature and pressure
Is the relative attraction that an atom in a molecule has for the shared pair of electrons in a covalent bond
States that at constant pressure the volume of a fixed mass of gas is directly proportional to its temperature measured in the Kelvin Scale ---> As temperature increases, volume increases.
One mole of a substance always contains 6 x 1023 particles (Atoms, Ions or Molecules)
A substance that is made up of 2 or more different elements that are combined together chemically.
Standard Temperature and Pressure
Standard Temp. - 275K (00C)
Standard Pressure.- 101,325 Pa (101kPa)
Relative Molecular Mass
The sum of all the relative atomic masses of all atoms in the compound
The process by which particles of a substance spread through a solid liquid or gas
Half distance between the nuclei of 2 atoms of the same element that are joined together by a single covalent bond.
Is a charged atom or groups of atoms
Are atoms of the same element that have different mass numbers due to different numbers of neutrons in the nucleus
A substance that cannot be broken down into simpler substances by chemical means
Relative Atomic Mass
This average mass of an atom is measured relative to the mass o's 1/12 of the C-12 isotope
Pressure of a gas is the force exerted by the gas on each unit area of its container. Measure using Pascal (101,325 Pa or 101 kPa; 1kPa=1000Pa)
A gas that obeys all the assumptions of the kinetic theory of gases under all conditions of temperature and pressure ( PV=nRT)
Defined as a substance that has no well defined boundaries but diffuses rapidly to fill any container in which its placed.
The chemical bond formed by the sharing of electrons
The force of attraction between oppositely charged ions in a compound
Bonding between one molecule and another --> Van Der Waals, Dipole Dipole and Hydrogen Bonding
Inner shell of electrons shield the outer electron from attracting to the nucleus
First Ionisation Energy
The MINIMUM amount of energy required to remove the most loosely bound electron from a neutral gaseous atom in its ground state.
Shows the arrangement of electrons in each main energy level in an atom of that element.
The fixed energy value that an electron in an atom may have
Second Ionisation Energy
Is the amount of energy required to remove the 2nd electron from the positive ion formed when the 1st electron was removed.