1. Periodic Trends: Atomic & Ionic Radii
301 Chemistry

2. Do Now:

4. Atomic Radii
Measured by halving the distance between two nuclei in a bond.

5. Decreases across the period
Atomic Radii Trends
Decreases across the period
Increases down a group

6. Decreases across a period
The number of protons increases and electrons are in the same energy level
This increases the electrostatic attractions and the electrons are pulled in closer to the nucleus
Decreasing the radius of the atom

7. Increases down a group
The atoms in the group have more electron shells, therefore the valence electrons are further from the nucleus
The valence electrons are ‘shielded’ from the positive nucleus by the inner electron shells, so the electrostatic attraction between the electrons and nucleus is decreased.

8. Ionic Radii - Cations

9. Ionic Radii - Cations
Cations are always smaller than their corresponding atoms
There are less electron shells so the valence electrons are closer to the nucleus.

10. Ionic Radii - Anions

11. Ionic Radii - Anions
Negative anions are always larger than their parent atoms
There are more electrons in the valence shell – there is more electron-electron repulsion increasing the radii