1. Extra Covalent Bonding Info

2. Exception Time Beryllium and the elements from Group 13 (B, Al, Ga, In, Tl) will engage in covalent bonding but will form electron deficient species. Their central atoms will often not attain noble gas configuration through simple covalent bonding. Consider BH 3 Boron has 3 valence electrons and each hydrogen has 1. After the 3 covalent bonds are formed we have a neutral molecule. B does not have a noble gas configuration, it cannot obtain it and remain neutral.

3. Electronegativity and Polarity Purely Covalent Bond –Equal sharing of one or more electron pairs Non-Polar Covalent Bond –Almost equal sharing of one or more electron pairs Polar Covalent Bond –Unequal sharing of one or more electron pairs  ENBonding Character > 1.7Ionic 0.4 – 1.7Polar Covalent < 0.4Non-Polar Covalent 0Purely Covalent

4. Electronegativity and Polarity There are some exceptions to these rules: –HF – the electronegativity difference is >1.7 but the bond is polar covalent –LiH – the electronegativity difference is <1.7 but the bond is ionic

5. Resonance When we can draw equivalent structures for the same compounds, we simply “move” a multiple bond. We say resonance occurs. Consider O 3 (ozone) The double bond can be drawn on the “left” or the “right” Try to draw the Lewis Structure for the nitrate ion NO 3 -