Bell Ringer 1. How many valence electrons does N have? 2. Which of the 3 “classes” on the periodic table displays properties of both metals and nonmetals? 3. Which Group on the periodic table has the most reactive metals? Why are they the most reactive? 4. Which Group has the most reactive nonmetals? Why?

Periodic Table TRENDS

The Periodic Table and Atomic Radius

Period Trend: Atomic Radius

Ionization energy Ionization energy Ionization energy is the amount of energy needed to remove an electron from an atom. The ionization energy decreases as you move down a group. Why? ◦ The size of the atom increases. ◦ Electron is further from the nucleus.

The ionization energy increases as you move from left to right across a period. Why? ◦ Attraction of the electron to the nucleus increases. ◦ Becomes easier to gain an electron(s) than lose one. Ionization Energy

Periodic Trend: Ionization Energy

Electronegativity: the ability of an atom to attract (or gain) an electron

Electronegativity Electronegativity decreases as you move down a group. Electronegativity of the Group A elements increases as you move across a period from left to right.

Periodic Trend: Electronegativity

Trends Atomic Mass Increases Atomic Radius Decreases Ionization Energy Increases Electronegativity Increases Atomic Mass Increases Atomic Radius Increases Ionization Energy Decreases Electronegativity Decreases