1. Periodic Trends Atomic radii Ionization Energy
Multiple Ionization Energy
Electron Affinity
Electronegativity

2. Atomic Radius
Is an estimate of the size of an atom from its nucleus to its outer perimeter (measured in pm or m)
Trend: Increases to the left and down
Reason: core charge increases across the period pulling electrons closer in and added shells increase distance and decrease pull

3. Ionization energy
The energy needed to remove an electron from the gaseous atom.
1st ionization energy removes electron with the smallest amount of attraction to the nucleus
The atom become a positive ion- cation when it loses an electron
Ionization energy is measured in MJ/mol

4. Ionization energy (cont)
Trend: Ionization energy increases as you go right and up
Reason: atomic radius decreases, electrons are pulled in by greater nuclear charge
Reason: atomic radius increases, pull by far away nucleus decreases as well as screening makes it easier to remove an electron

5. Electron Affinity
Electron affinity is the energy released when an electron is added to a gaseous atom (measured in kJ/mol).
The atom becomes a negative ion (anion) when it accepts an electron
Trend: Electron affinity increases as you go right and up.
Reason: Across a period, radius decreases, atomic charge increases, greater pull.

6. Electron affinity (cont)
Trend: As you go down a group, electron affinity decreases
Reason: Greater radius, decreased nuclear pull and electrons circling in far orbits make adding an electron not as desirable

7. Electronegativity
Property that determines the relative strength of attraction by an atom of a bonding electron pair in a chemical compound
F-F equal sharing of electrons in the covalent bond. H-F unequal sharing of electrons. Fluorine has a greater attraction and electrons stay closer to fluorine than hydrogen in the covalent compound.

8. Electronegativity (cont)
Trend: Increases across a period
Reason: core charge
Trend: Decreases as you go down a group
Reason: far orbits have a decreased attraction to far away nucleus

9. Multiple Ionization energy
Every electron can be successively removed from an atom- 1st, 2nd, 3rd… ionization energy
At each successive removal, ionization energy increases
Trends are consistent with 1st ionization energy and the model of the atom