1. Even More About the Periodic Table
Periodic Trends

2. Trends in Atomic Size
Atomic radius - one-half the distance between the nuclei of two atoms of the same element when the atoms are joined
In general, atomic size increases from top to bottom within a group and decreases from left to right across a period.

3. Trend in Ionic Size
Cations are always smaller than the atoms from which they form.
Anions are always larger than the atoms from which they form.

4. Trends in Ionization Energy
First ionization energy tends to decrease from top to bottom within a group and increase from left to right across a period.

5. Trends in Electronegativity
In general, electronegativity values decrease from top to bottom within a group. For representative elements, the values tend to increase from left to right across a period.

7. Summary of Trends
The trends that exist among these properties can be explained by variations in atomic structure.
The increase in nuclear charge within groups and across periods explains many trends.
Within groups an increase in shielding (distance from the nucleus) has a significant effect

8. Ionization energy INCREASES Electronegativity INCREASES
Atomic size DECREASES
Ionization energy INCREASES
Electronegativity INCREASES
Nuclear charge INCREASES
Shielding is constant 1 18 2 13 14 15 16 17
Ionization energy DECREASES
Electronegativity DECREASES
Nuclear charge INCREASES
Atomic size INCREASES
Shielding INCREASES
Ionic size INCREASES
Size of cations decreases
Size of anions decreases

9. Periodic Trends Notes

10. Electron Shells
Ground State means no electrons are where they are not supposed to be.
Excited state is when the electrons absorb energy and jump up to a higher electron shell or energy level.
When electrons fall back down to the ground state they emit a specific amount of energy which is noticed as a specific color (or colors) of light.