1. Atomic Radii Ionic Radii Ionization Energies Electronegativity
Periodic Trends
Atomic Radii
Ionic Radii
Ionization Energies
Electronegativity

2. Atomic Radius- used to estimate size of atom
half the distance between two nuclei of identical atoms that are bonded together.
Why?

3. Atomic Radii - Periodic Trends
Notice atomic radii increase as we go down a group.
Why?
Notice they decrease as we go across a period from left to right even though we’re adding particles to the succeeding atoms.
As we add more energy levels, size of atom increases
As we move across period, atomic # increases. The attraction between the nucleus and the outer electrons increases as the nuclear charge increases.

4. Ionic radius Cation vs. anion
Atoms – lose electrons ,+ ions, smaller radius
Atoms – gain electrons, -ions, larger radius
Trend???

5. Ionization Energy energy required to remove an electron from an atom
Can you predict which elements would require the least energy to remove an electron and which would require the most?

6. Ionization energy
Period trend – increases as move across period, increased nuclear charge, higher +charge more strongly attracts electrons
Group trend – decreases as move down a group; electrons in higher energy levels are farther from the nucleus making them easier to remove

7. Ionization Energy Factors affecting ionization energies include:
Nuclear charge - The larger the nuclear charge the greater the ionization energy.
Shielding effect - The greater the shielding effect, the less the ionization energy.
Radius - The greater the distance between the nucleus and the outer electrons of an atom, the less the ionization energy.

8. Shielding effect Nuclear force absorbed By inner shell electrons e- e-
Nucleus
Outermost energy level with valence electron
Inner (shielding) energy levels

9. Practice problems
Pg. 165 #’s16-18

10. Electronegativity
Electronegativity is the measure of an atom in a chemical compound to attract electrons.
Increases as move up a group and across a period from left to right