1. Atomic Radius
Definition: The distance from the center of an atoms nucleus to it’s outermost electron
Radius decreases across a period
Measure of atomic size
Radius increases down a group
Each row on the periodic table adds a “shell” or energy level to the atom

2. Table of Atomic Radii

3. Electronegativity
Definition: A measure of the ability of an atom in a chemical compound to attract electrons
Electronegativity tends to increase across a period
As radius decreases, electrons get closer to the bonding atom’s nucleus
Electronegativity tends to decrease down a group or remain the same
As radius increases, electrons are farther from the bonding atom’s nucleus

4. Periodic Table of Electronegativities

5. Reactivity
Definition: how likely or vigorously an atom is to react with other substances.
Metals
Period - reactivity decreases as you go from left to right across a period.
Group - reactivity increases as you go down a group
Why? The farther to the left and down the periodic chart you go, the easier it is for electrons to be given or taken away, resulting in higher reactivity.
Non-metals
Period - reactivity increases as you go from the left to the right across a period.
Group - reactivity decreases as you go down the group.
Why? The farther right and up you go on the periodic table, the higher the electronegativity, resulting in a more vigorous exchange of electron.

6. Reactivity Exception
Noble Gases
Noble gases are not reactive (inert) because they have a full valence shell. This means they cannot donate, or accept electrons in a chemical reaction. They can, however, bond with other noble gases.

7. Period Trend: Atomic Radius

8. Periodic Trend: Electronegativity

9. Periodic Trend: Reactivity
Reactivity decreases (metals)
Reactivity increases (nonmetals)
Periodic Trend: Reactivity
Reactivity decreases (non metals
Reactivity increases (Metals)
IMPORTANT:
Noble Gases
NOT reactive
(inert)