Ionization Energy Def: the energy required to remove an e- from a gaseous atom. 1st ionization energy is the energy required to remove the 1st e- . More energy is required to remove e-’s held more tightly by the nucleus.

Ionization Energy (continued) So, how do you think ionization energy would change across periods? Answer: Increases, due to increasing charge in the nucleus while adding electrons to the same principal energy level (same reasoning as atomic radius) Down groups? Answer: Decreases, due to same reasoning as atomic radius

Octet Rule If Na loses an electron: What is its charge? What is its new electron configuration? How many electrons are present in its highest principal energy level (valence electrons)? Octet Rule: atoms gain, lose, or share electrons in order to acquire a full set of 8 valence electrons.

Electronegativity Def: the relative ability of an element’s atoms to attract electrons in a chemical bond Most electronegative element is fluorine. Least electronegative is francium. What do you think the trend is within periods? Within groups?