1. Periodic Trends Mr. Chan Northwestern University To insert your company logo on this slide From the Insert Menu Select “Picture” Locate your logo file Click OK To resize the logo Click anywhere inside the logo. The boxes that appear outside the logo are known as “resize handles.” Use these to resize the object. If you hold down the shift key before using the resize handles, you will maintain the proportions of the object you wish to resize.

2. How Periodic Table is Periodic How are electron configurations related in the periodic table? How are electron configurations related in the periodic table? Noble gases Noble gases All configurations end in s2 or p6 All configurations end in s2 or p6 Representative elements Representative elements All end in s or p All end in s or p Transition metals Transition metals All end d or f All end d or f Groups of elements end in same configurations Groups of elements end in same configurations

3. Periodic Trends Certain patterns exist in periodic table Certain patterns exist in periodic table Atomic Size (Atomic Radius) Atomic Size (Atomic Radius) Half the distance between nuclei of two like atoms in diatomic molecule Half the distance between nuclei of two like atoms in diatomic molecule Trend: Trend: Down group (increases) Down group (increases) Across period (decreases) Across period (decreases) Ionic size Ionic size Cations (loss of electrons) Cations (loss of electrons) Anions (gain electrons) Anions (gain electrons)

4. Ionization Energy Energy required to overcome the attraction of the nuclear charge and remove an electron from a gaseous atom Energy required to overcome the attraction of the nuclear charge and remove an electron from a gaseous atom Trend Trend Down group (decreases) Down group (decreases) Across period (increases) Across period (increases) Discuss nuclear charge, shielding effect Discuss nuclear charge, shielding effect

5. Electronegativity Tendency for atoms of element to attract electrons when they are chemically combined Tendency for atoms of element to attract electrons when they are chemically combined Trend Trend Down group (decreases) Down group (decreases) Across group (increases) Across group (increases)

6. Summary of Periodic Trends