1. Periodic Trends - Part II
Atomic Radii
Ionization Energies
Electron Affinity
Ionic Radii
Electronegativity

2. Atomic Radius
Atomic radius is half the distance between two nuclei of identical atoms that are bonded together.
Why?
Remember - atoms are not solid balls!

4. 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.

5. Atomic Radii - Periodic Trends+ +

6. Atomic Radii - Periodic Trends+ +

7. Neon
Helium
Argon
Krypton
Xenon
Radon
Atomic number
Ionization energy

8. Ionization Energy
An ion is an atom or molecule that has gained or lost an electron.
The energy required to remove an electron from an atom is the ionization energy.
Can you predict which elements would require the least energy to remove an electron and which would require the most?

9. 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.
Sublevel - An electron from a full or half full sublevel requires additional energy to be removed.

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

11. Sublevels
Atoms with filled or half filled sublevels have greater stability than others with different configurations.
Chromium s d
[Ar]4s23d4
Is actually
[Ar]4s13d5

12. Neon
Helium
Argon
Krypton
Xenon
Radon
Atomic number
Ionization energy

13. Electron Affinity
The attraction of an atom (in the gaseous state) for an electron is electron affinity. (Opposite of Ionization energy).
The same factors that affect ionization energies also affect electron affinity.

14. Ionic Radii A positive ion is known as a cation.
How could an atom have a positive charge?
A negative ion is called an anion.
How could an atom have a negative charge?
What affect would these have on radii?
See text page 149.

15. Electronegativity
Electronegativity is the measure of an atom in a chemical compound to attract electrons. .

16. Electronegativity
Electronegativity is the a measure of an atom in a chemical compound to attract electrons. .

17. Electronegativity
Electronegativity is the measure of an atom in a chemical compound to attract electrons.