1. Periodic Trends

2. Periodic Trends What is a trend?
A trend is the general direction in which something tends to move.

3. Periodic Trends
The elements on the Periodic Table of Elements show many trends in their physical and chemical properties.
Across the rows (periods or series)
Down the columns (groups or families)

4. Atomic Radius
½ the distance between the nuclei of 2 like atoms in a diatomic molecule
The atoms of the 8 main groups are shown here.

5. Atomic Radius - Groups
Atomic radius increases as you move down a group
Why?
More electrons in more Principal Energy Levels
Atomic size increases

6. Atomic Radius - Periods
Atomic radius decreases as you move across a period
Why?
(-) electrons increase, but so do (+) protons !!!
Increased (+) nuclear charge pulls the (-) electrons closer to the nucleus
Atomic size decreases

7. Ionization Energy
Is the Energy needed to remove an electron from an atom
Increases from left to right on the periodic table
Also increases going up the bottom to the top of the periodic table

8. Ionization Energy

9. Electronegativity - Periods
Electronegativity is the strength of which an element pulls electrons.
Electronegativity increases going left to right across the periodic table.
Electronegativity decreases going down a group Li Be B C N O F
1.0
1.5
2.0
2.5
3.0
3.5
4.0

10. Electronegativity - Groups
Electronegativity decreases going down a group H Li Na K Rb Cs Fr

11. Electronegativity

12. Electronegativity