3.10-3.12: Periodic trends:

3.10: The size of atoms and ions:

  • Metallic radius: the atomic radius of a metal

    • Half the distance between the nuclear centers in a solid metal

    • The atomic radius of elements increases with increasing atomic number

  • Move left to right: each element gains an electron

    • Atomic radii don’t increase; they actually decrease in size as the atomic number increases across a row

    • Caused by:

      • Increasing effective nuclear charge: atomic number increases, so does the positive charge of the nucleus. 

      • And increasing repulsion between valence electrons: as the atomic number increases, so does the number of valence electrons

  • Isoelectronic ions: two species that have the same electron configuration

  • Anions are larger than parent atoms, so any negative charge on an atom will cause the new ion to be larger than the parent atom.

  • larger right to left. 

3.11: Ionization energies and photoelectron spectroscopy:

  • Ionization energy (IE): the energy needed to remove 1 mole of electrons from 1 mole of gas-phase atoms or ions in their ground states

    • Removing electrons consumes energy

    • Negative always attracts to a positive nucleus, so overcoming attraction requires energy

  • First ionization energy (IE1): amount of energy needed to remove 1 mole of electrons from 1 mole of atoms to make 1 mole of electrons from 1 mole of atoms to make 1 mole of 1+ cations

  • Second ionization energy (IE2): energy needed to remove 1 mole of electrons from 1 mole of 1+ cations to make 1 mole of 2+ cations

  • A combination of larger atomic size and more shielding by inner-shell electrons leads to decreasing IE1 values from top to bottom in every group of the periodic table

  • IE2 is always greater than IE1 because multielectron atoms are always greater in IE2 than IE1

  • Photoelectron spectroscopy (PES): a technique for determining the binding energies of electrons with an atom

  • Photoelectron spectra: a graph plotting the number of electrons ejected by a metal as a function of binding energy

3.12: Electron Affinities:

  • Electron affinities (EAs): the energy change that occurs when 1 mole of electrons combines with 1 mole of atoms or ions in the gas phase

  • negatively charged electron + positively charged nucleus = ion with lower electrostatic energy (more stable)

  • Group 18 atoms have to add energy since they have full valence-shell orbitals