Honors Chemistry Unit 3: Periodic Trends

Warm-up: Review of the periodic table which includes:
- Sketching an outline.
- Labeling groups/families.
- Labeling metals vs. nonmetals.
- Labeling valence electrons and most common ion.
Homework (At home):
- Work on INSPIRE U3, due Monday, 9/22 at 10:00pm.
Exams:
- Unit 3 Exam is scheduled for Wednesday, 9/24 or Thursday, 9/25.
Submission:
- Turn in graphs stapled IN ORDER for:
  - Atomic radius
  - Ionization energy
  - Electronegativity

Definition: These are the outermost electrons in an atom. They are directly involved in chemical bonding and are primarily responsible for determining an element's chemical properties.
Pattern in Groups:
- Group 1: 1 valence electron
- Group 2: 2 valence electrons
- Groups 13-18: The number of valence electrons generally corresponds to the last digit of the group number (e.g., Group 13 has 3, Group 14 has 4, Group 17 has 7, Group 18 has 8).

Definition: Atomic radius refers to the size or radius of an atom. It is measured from the center of the nucleus to the outermost electron shell.
General Trends:
- Within a Group (Top to Bottom): Atomic radius generally increases as you go down a group. The biggest atom (Francium, Fr) is located at the bottom-left of the periodic table.
- Across a Period (Left to Right): Atomic radius generally decreases as you go across a period. The smallest atom (Helium, He) is located at the top-right of the periodic table.
Driving Forces for Trends:
- Effective Nuclear Charge (for Left to Right trend): As the number of protons in the nucleus increases across a period, the positive charge of the nucleus becomes stronger. This stronger pull from the nucleus for the electrons causes the electron cloud to contract, resulting in a smaller atomic radius.
- Electron Shielding (for Down a Group trend): As you move down a group, atoms gain additional electron shells. The inner-shell electrons