1. Warm Up
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

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

3. 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.

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

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

6. 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)

7. 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

8. 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

9. 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

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

11. 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

12. 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 mL vinegar

13. Homeroom
One-on-One grade check
Quote of the week