Warm Up 10-5-17 How many valence electrons do elements in the alkali and halogen group have? Which of these elements are metal? Al, As, Cl, Li Are all atoms the same size? Agenda -Turn in lab reactivity -Notes Unit 3-3 Homework Today – Test Correction! -Quiz next class Unit 3

Activity Breaking the code Arrange your cards (elements) just like the periodic table Look for commonalities on why elements are in the same groups

Activity Breaking the code Talk about the patterns/trends you can find going horizontal (from left to right) on the periodic table. Talk about the patterns/trends you can find going vertical (from top to bottom) on the periodic table.

Unit 3-3 Periodic Trends Atomic radius Ionization energy Electronegativity Electron affinity

Atomic Radius Trend Radius decreases Radius Increases Radius decreases Based on the picture what trend do you see? In term of atomic size

Periodic Trends Atomic Radius: The estimated distance from the nucleus to the outer most electrons Increases down a group As electrons energy levels are added, the atom becomes larger Decreases across a period # protons increases, stronger force to pull electrons closer to the nucleus Pass around magnets Positive protons and negative electrons attract each other (opposite attract - boys and girls)

Periodic Trends Electronegativity - the ability of an atom to attract electrons to itself Decreases down a group Increases across a period How many like to have a car or an A in chemistry? Decreases down a group because the radius is too big, harder to attract electrons

Periodic Trends Ionization Energy - The energy required to remove one electron from an atom or ion Decreases down a group Electrons are farther from the nucleus and easier to remove Increases across a period Positive protons and negative electrons attract each other (opposite attract - boys and girls) Protons can’t attract electrons that are far away - long distance relationship doesn’t work

Periodic Trends Electron Affinity - the energy change that occurs when an electron is added to a neutral atom Decreases down a group Increases across a period Ask students to tell their partner which of the four trends are similar to each other. Discuss

Trends Summarize See board See board (diagonal lines for trends)

Check In Consider the following elements: Ca, Fe, Ga, Br Largest radius? Smallest radius? Highest electronegativity? Lowest ionization energy? Largest radius = Ca smallest = Br Highest electronegavity = Br Lowest ionization = Ca

Assignments Summary: Explain what atomic radius is and why ionization energy trend is opposite of the radius? Worksheet trends at least front side Quiz topics for next class (5 questions): Finding valence electrons Group names and properties Periodic trends Conservation of mass lab electronic scale 1 balloon 50 mL flask 5 g baking soda 25ml graduated cylinder 15 mL vinegar

Homeroom 10-4-17 One-on-One grade check Quote of the week