1. Periodic Trends

2. Periodic Trends
Electron configurations are able to cause periodic variations in elemental properties...

3. Periodic Trends
Valence electrons - electrons that may be lost/gained/shared when chemical compounds are formed

4. Periodic Trends Valence electrons
Period  As we go across a period, the number of valence electrons increases.

5. Periodic Trends Valence electrons
Group  As we go down a group, we find that the number of valence electrons stays constant.

6. Periodic Trends
Size of the atomic radius – one-half the distance between the nuclei of identical atoms joined in a molecule

7. Periodic Trends Size of the atomic radius –
Period  As we go across a period, the general trend is for the atomic radii to decrease.
This trend is due to the increasing positive charge in the nucleus – stronger ability to pull in the electrons.

8. Periodic Trends Size of the atomic radius –
Group  As we go down a group, there is a general increase in atomic radii. This happens because we are seeing more and more energy levels being added.

9. Periodic Trends
Ionization energy – energy required to overcome nuclear attraction and remove an electron from a gaseous element
Fluorine is the most electronegative element and is assigned a value of 4. All other values are calculated relative to this value.

10. Periodic Trends Ionization energy
Period  As we go across a period, the general trend is for the ionization energy to increase.
This means that the elements on the right side of the Periodic table “want” electrons more than the elements on the left.

11. Periodic Trends Ionization energy
Group  As we go down a group, there is a general decrease in ionization energy.
This is also due to size considerations. Larger atoms have more “shielded” nuclei than smaller elements.

12. Periodic Trends
Electronegativity - measure of the power of an atom in a chemical compound to attract electrons
Fluorine is the most electronegative element and is assigned a value of 4. All other values are calculated relative to this value.

13. Periodic Trends Electronegativity
Period  As we go across a period, the general trend is for the electronegativity to increase.
This means that the elements on the right side of the Periodic table “want” electrons more than the elements on the left.

14. Periodic Trends Electronegativity
Group  As we go down a group, there is a general decrease in electronegativity.
This is also due to size considerations. Larger atoms have more “shielded” nuclei than smaller elements.