1. Periodic Table
Chapter 6

2. History
Dimitri Mendeleev (a Russian scientist) usually gets credit for arranging the elements on the periodic table according to increasing atomic mass.
His periodic law stated that the properties of elements were periodic functions of their increasing atomic mass.

3. Dimitri Mendeleev

4. Groups Groups or families of elements have similar properties.
This is due to similar outer electron arrangement.
Outer electrons are called valence electrons.
They are vertical columns on the periodic chart.

5. Families and Groups

6. Periods Elements are also arranged in horizontal rows called periods.
The row or period signifies the number of energy levels being occupied by the electrons of a particular element.

7. Henry Mosely
A young, English chemist who used X-ray diffraction to determine that the number of protons was responsible for the identity of an element.
Today’s periodic chart is arranged according to increasing atomic number.
Modern periodic law states that the properties of the elements are periodic functions of their increasing atomic numbers.

8. Henry Moseley

9. Trends on the Periodic Table

10. Ionization Energy
Energy required to remove the outermost electron from an atom.
Measured in kJ/mol.
Generally increases from left to right across a period.
Decreases as you move down a column.

11. Electron Affinity the attraction of an atom for an electron.
Same unit and same trend as ionization energy.
Metals want to get rid of electrons; nonmetals WANT electrons!

12. Electronegativity
Relative tendency of an atom to attract electrons to itself when bound with another atom.
Same trend, NO UNIT!

13. Trends in Electronegativity

14. Electronegativity Table

15. Atomic Radius
The distance from the center of an atom’s nucleus to its outermost electron.
Radius size tends to decrease across a period due to increasing nuclear charge (this attraction pulls the electrons in closer, making the “circle” get smaller).
Size increases as you move down a group due to the addition of another energy level (like adding a story to a house)

16. Atomic Radius

17. Ionic Radius
Metallic ions lose electrons and are smaller compared to the atoms from which they come from.
For ex., Na+ is smaller than Na since it loses an electron!
Nonmetallic ions gain electrons and are LARGER compared to the atoms they come from. Cl- is larger than Cl

18. Ionic Radius