Bonds

1. Bonds

2. Bond Energy • Bond Energy: the energy required to break a bond • What type of bond has the highest bond energy? (Single, Double, or Triple) C-C 348 kJ C=C 614 kJ CΞC 839 kJ

3. Bond Length • Bond Length: the distance between the nuclei of two bonded atoms • What type of bond is the longest? (Single, Double, or Triple) C-C 154 pm C=C 134 pm CΞC 120 pm

4. VSEPR

5. VSEPR • VSEPR: Valence Shell Electron Pair Repulsion • The pairs of valence electrons in a molecule want to be as far apart from each other as possible. • VSEPR allows us to predict the geometry or shape of the molecule.

6. VSEPR • To determine the shape of the molecule you need to count the number of bonded atoms and the number of lone pairs on the center atom of the Lewis structure. • A double or triple bond only counts as 1bonded atom.

7. 2 Bonded Atoms 0 Lone Pairs • Ex: CO2 • This is a linear shape • Linear molecules have a bond angle of 180° 180° ●● O C O ●● ●● ●●

8. 3 Bonded Atoms 0 Lone Pairs • Ex: CH2O • This is a trigonal planar shape • Trigonal planar has a bond angle of 120° H C O H 120° ●● ●●

9. 2 Bonded Atoms 1 Lone Pair • Ex: HNO • This is a bent shape • This bent has a bond angle of 120° ●● N H O ●● ●● 120°

10. 4 Bonded Atoms 0 Lone Pairs • Ex: CH4 (AKA methane) • This is a tetrahedral shape • Tetrahedral has a bond angle of 109.5° H H C H H 109.5°

11. 3 Bonded Atoms 1 Lone Pair • Ex: NH3 (AKA ammonia) • This shape is trigonal pyramidal • Trigonal pyramidal has a bond angle of 109.5° ●● H N H H 109.5°

12. 2 Bonded Atoms 2 Lone Pairs • Ex: H2O (AKA water) • This shape is bent • This bent has a bond angle of 109.5° ●● ●● O H H 109.5°

13. Practice • Draw the Lewis structure and predict the shape and bond angle for the following molecules: • SiCl4 • SI2 • HCN • BrPS