Ionization Energy: Ion: Positively or negatively charged particle formed by the loss or gain of electrons. Two Types of Ions: Cation: Positively charged particle formed by the loss of electrons (Na+1). Anion: Negatively charged particle formed by the gain of electrons (Cl-1). Ionization Energy: Amount of energy required to remove an electron from an atom. Ionization is inversely proportional to atomic radius. Group Trend for Ionization Energy (Top to Bottom): As you go down a group or family on the periodic table, ionization energy decreases, because the atoms are larger so the electrons are farther from the nucleus making it easier to remove electrons. Periodic Trend for Ionization Energy (Left to Right): As you go across a period on the periodic table, ionization energy increases, because the atoms are smaller so the electrons are closer to the nucleus making it more difficult to remove electrons. Exceptions: 1) Group 3A has a lower ionization energy than Group 2A, because Group 2A has a filled “s” subshell, so it resists losing an electron. 2) Group 6A has a lower ionization energy than Group 5A, because Group 5A has a half-filled “p” subshell, so it resists losing an electron. 1A, 3A, 2A, 4A, 6A, 5A, 7A, 8A Example: Place the following elements in order of increasing ionization energy: Astatine (At), Fluorine (F), Iodine (I), Bromine (Br), Chlorine (Cl) Astatine (At), Iodine (I), Bromine (Br), Chlorine (Cl), Fluorine (F) Example: Place the following elements in order of increasing ionization energy: Magnesium (Mg), Aluminum (Al), Sodium (Na), Phosphorus (P), Sulfur (S), Chlorine (Cl), Silicon (Si), Argon (Ar) Sodium (Na), Aluminum (Al), Magnesium (Mg), Silicon (Si), Sulfur (S), Phosphorus (P), Chlorine (Cl), Argon (Ar) Example: Place the following elements in order of increasing ionization energy: Bismuth (Bi), Antimony (Sb), Nitrogen (N), Phosphorus (P), Arsenic (As) Bismuth (Bi), Antimony (Sb), Arsenic (As), Phosphorus (P), Nitrogen (N) Example: Place the following elements in order of increasing ionization energy: Strontium (Sr), Tellurium (Te), Chlorine (Cl), Iodine (I), Antimony (Sb), Tin (Sn), Indium (In), Rubidium (Rb), Francium (Fr) Francium (Fr), Rubidium (Rb), Indium (In), Strontium (Sr), Tin (Sn), Tellurium (Te), Antimony (Sb), Iodine (I), Chlorine (Cl) Example: Place the following elements in order of increasing ionization energy: Calcium (Ca), Arsenic (As), Bromine (Br), Selenium (Se), Rubidium (Rb), Potassium (K), Gallium (Ga), Fluorine (F) Rubidium (Rb), Potassium (K), Gallium (Ga), Calcium (Ca), Selenium (Se), Arsenic (As), Bromine (Br), Fluorine (F) .