ionization energy - measures amount of energy needed to lose an electron  

• more difficult to remove electrons w/ greater ionization energy
• more energy needed to remove each subsequent electron
• sharp increase in ionization energy needed to remove inner shell electrons
  • inner shell electrons much closer to nucleus
• I1 generally increases w/ atomic number on each row
• I1 decreases as atomic number increases down a group
• representative elements have larger range of I1 than transition elements
• smaller atoms tend to have higher ionization energies (electrons closer to nucleus)

ion electron configurations - electrons removed from largest available quantum number first  

• electrons added to lowest available quantum number first

electron affinity - energy change when electron is added to a gaseous atom  

• measures attraction of atom for added electron
• usually negative (energy usually released when electron is added), but can be positive for noble gases (anion higher in energy than separated atom/electron)
• halogens have the most negative electron affinities
• noble gases have positive electron affinities (when adding an electron would place it on a new energy subshell)
• group 5A (w/ 1/2 filled subshells) have electron affinities either positive or less negative than group 4A
• doesn't change much going up/down a group