The document discusses periodic trends in atomic properties according to the periodic table. It explains that atomic radius decreases across a period as effective nuclear charge increases due to shielding effects, while radius increases down a group as each row adds a new shell. Ionization energy tends to increase across a period as removal of electrons becomes more difficult, and decreases down a group as outer electrons are farther from the nucleus. Electronegativity also increases across a period but decreases or stays the same down a group as distance from the nucleus increases. Positively charged cations are smaller than their parent atoms, while negatively charged anions are larger.

1. Periodic Trends

2. CA StandardsStudents know how to use the periodic table to identify trends in ionization energy, electronegativity, and the relative sizes of ions and atoms.

3. Atomic RadiusDefinition: Half of the distance between nuclei in covalently bonded diatomic molecule Radius decreases across a period

4. Increased effective nuclear charge due to decreased shielding

5. Radius increases down a group

6. Each row on the periodic table adds a “shell” or energy level to the atomTable of Atomic Radii

7. Period Trend:Atomic Radius

8. Ionization EnergyDefinition: the energy required to remove an electron from an atomTends to increase across a period

9. As radius decreases across a period, the electron you are removing is closer to the nucleus and harder to remove

10. Tends to decrease down a group

11. Outer electrons are farther from the nucleus and easier to removePeriodic Trend:Ionization Energy

12. ElectronegativityDefinition: A measure of the ability of an atom in a chemical compound to attract electronsElectronegativity tends to increase across a period

13. As radius decreases, electrons get closer to the bonding atom’s nucleus