1. Information we gather from the organization of the table
Periodic Trends
Information we gather from the organization of the table

2. Atomic radius- size of the atoms
Decreases from left to right across a period- increasing Zeff (nuclear charge) in same energy level pulls electrons closer to nucleus.
Increases top to bottom in group – added energy level means larger cloud and shielding effect of core electrons
Zeff = p+ - s (protons – core electrons)
Period has increasing p+ but same core

4. Ionic radius – size of ions
Follows same trends for same reasons
With halides making -1 ions, the radius increases slightly due to the additional electron increasing repulsion and the electrons requiring more space.

5. Ionization energy- absorbed to remove outermost electron
ΔE1 to remove 1st electron
ΔE2 to remove 2nd electron
More difficult to remove successive electrons as they have a greater attraction to nucleus.
Trend is opposite atomic radius. Smaller atoms on right have stronger nuclei, and require more IE.
Irregularities do occur across periods at beginning of p and p4

7. 1st IE B , 1st IE Be because B outer electron is located in 2p orbital which is higher in energy than 2s, and easier to remove.
1st IE N higher than 1st Ie O because O contains paired p electrons, which require energy to remain in same orbital (pairing energy). And it is easier to remove one of the paired electrons.

8. Electronegativity- attraction for pair of electrons in a bond.
Increases left to right- stronger nuclear pull, Zeff.
Decreases top to bottom- shielding and larger radius make Zeff less effective.

9. Electron affinity- PE change by addition of electron
Same trends as IE
Across periods increases left to right larger Zeff so electron will be pulled closer to nucleus, losing more potential energy.
Stronger nuclei at right, stronger pull and larger drop in PE so greater EA
Down group- less EA shielding