S3

• Ionisation energy


  the energy required to remove an electron from an one mole atom in the gaseous state (to form one mole of gaseous 1+ ions)  kJ mol^-1
• Periodicity


  a repeating pattern of properties
• Electron affinity


  the enthalpy change when an electron is added to an atom in the gaseous state (exothermic process)
• Lattice enthalpy


  the energy required to form one mole of an ionic compound from its ions in their gaseous state
• Isoelectronic ions


  atoms, ions or molecules that have the same electronic structure and same number of valence electrons
• Electronegativity


  a measure of the tendency of an atom to attract a bonding pair of electrons
• Isolated atom


  a group of atoms that exists separately without any bonding with other atoms= Noble gases
• The ionic bond


  an electrostatic force between positive and negative ions
• Lattice


  a 3-dimensioned repeating structure made up of particles held together by very strong interactions
• shielding effect

  the decrease in the force of attraction exerted by the nucleus on the valence electrons due to the presence of electrons in the inner shells
• Ligands


  Lewis bases with a lone pair of electrons that they can donate to a central metal ion
• Isotopes


  elements that have same number of protons but different number of neutrons
• Amphoteric


  a compound able to react both as a base and as an acid
• valence electrons


  the electrons in the outermost shell, or energy level, of an atom
• amphiprotic


  a proton-bearing molecule that is capable of donating its proton as well as accepting an additional proton
• octet


  the eight-electron arrangement in the outer electron shell of the noble-gas atoms
• actinides


  a series of metallic elements whose atomic numbers start from 89 and end at 103
• isoelectronic ions


  ions that have the same number of electrons
• atomic radius


  The distance from an atom's nucleus to the outermost orbital of one of its electrons. Usually measured as the half-distance between the nuclei of two of the same atoms bonded together
• effective nuclear charge


  the net positive charge pulling these electrons towards the nucleus
• when there is an energy level difference between two positive ions that are not in the same group, the Zeff plays more important rule
• decrease ionization energy when element increase energy level because electrons are further away from the nucleus, and there is less effective nuclear charge
• generally absolute values of electron affinity increase across a period and decrease down a group
• it is easier to remove an electron from paired sub-level than from non-paired sub-level because two electrons are repealing.
• elements are arranged into four blocks - s,p,d,f
• periods are numbered according to the outermost energy level (n) that is occupied by electrons
• the number of the principal energy level (n) and the number of the valence electrons in an atom can be deduced from its position on the periodic table
• elements are arranged in horizontal rows called periods
• elements are arranged in 18 vertical columns called groups
• group number refers to the valence electrons of the element