1. Atomic Size Ionic Size Ionization Energy Electronegativity
Periodic Table Trends
Atomic Size
Ionic Size
Ionization Energy
Electronegativity

2. Trends in Atomic Size Atomic Radius Trend:
Half the diameter of an atom
Measured in picometers (pm)
Trend:
Atomic size INCREASES down a group
WHY? Energy levels are added down a group
Atomic size DECREASES across a period
WHY? Protons are added moving across a period, increasing the pull of attraction from the nucleus and pulling electrons closer.

3. Trends in Atomic Size

4. Practice: Which atom is larger? Explain why. Barium or Magnesium?
ANSWER:
Barium or Magnesium?
Barium
Farther down the group
Sodium or Sulfur?
Sodium
Farther left in the period
Oxygen or Chlorine?
Chlorine
Farther down the group
Shielding effect
more energy levels

5. Trends in Ionic Size (Ionic Radius)
Cations are always SMALLER than the atoms from which they form.
Why? Because they have lost electrons.

6. Trends in Ionic Size (Ionic Radius)
Anions are always LARGER than the atoms from which they form.
Why? Because they have gained electrons.

7. Trends in Ionic Size (Ionic Radius)
Ionic size INCREASES down a group
WHY? Energy levels are added down a group
Ionic size DECREASES across a period
WHY? Protons are added moving across a period, increasing the pull of attraction from the nucleus and pulling electrons closer.
SAME TREND AS ATOMIC RADIUS!

8. Practice: Which ion is larger? Explain why. O or O2-? B or B3+?
ANSWER:
O or O2-?
Oxide ion (O2-)
Anion is larger than atom
B or B3+?
Boron atom (B)
Cation is smaller than atom
I1- or Br1-?
Iodide ion (I1-)
The iodide atom is farther down the group than the bromine atom

9. Trends in Ionization Energy
Energy needed to REMOVE an electron from an atom.
First Ionization Energy
Energy required to remove the first electron
Second Ionization Energy
Energy required to remove the second electron
Third Ionization Energy
Energy required to remove the third electron

10. Trends in Ionization Energy
Ionization Energy DECREASES down a group
WHY? Electrons that occupy higher energy levels are easier to remove because they are farther from the nucleus.
Ionization Energy INCREASES across a period
WHY? As protons are added across a period, the electrons are harder to remove because the nucleus is pulling them with a greater force.
OPPOSITE trend from Atomic & Ionic Radii!

11. IONIZATION ENERGY TREND
Helium has the highest ionization energy
Francium has the lowest ionization energy

12. Practice: Which has a greater first ionization energy?
ANSWER:
Potassium or Sulfur?
Sulfur
Farther to the right
Lithium or Francium?
Lithium
Farther to the top
Carbon or Phosphorus?
Carbon
Farther to the top
Fewer energy levels, stronger force of attraction

13. Trends in Electronegativity
Ability of an atom to attract electrons when the atom is in a compound.
When looking at this trend, we IGNORE the noble gases because they to not have the ability to attract electrons when in a compound since they have a filled s & p sublevels.

14. Trends in Electronegativity
Electronegativity DECREASES down a group
WHY? Electrons that occupy higher energy levels are easier to remove because they are farther from the nucleus.
Electronegativity INCREASES across a period
WHY? As protons are added across a period, the electrons are harder to remove because the nucleus is pulling them with a greater force.
SAME TREND AS IONIZATION ENERGY!

15. ELECTRONEGATIVITY TREND
Fluorine is the most electronegative element
Francium is the least electronegative element

16. Practice: Which has a greater electronegativity? Chlorine or Iodine?
ANSWER:
Chlorine or Iodine?
Chlorine
Farther to the top
Phosphorus or Magnesium?
Phosphorus
Farther to the right
Strontium or Potassium?
Strontium
Farther to the right
Stronger force of attraction