B. Ionic bonding and Structures of Ionic Compounds

1. B. Ionic bonding and Structures of Ionic Compounds • Polyatomic ions work in the same way as simple ions • The covalent bonds hold the polyatomic ion together so it behaves as a unit • Ionic Compounds Containing Polyatomic Ions

2. Writing Lewis Structures for Polyatomic Ions

3. 2- [SO4]2-

4. - [NO2]-

5. + [NH4]+

6. Objectives • SWBAT understandmolecular structure, be able to predictmolecular geometry from the number of electron pairs and to apply the VSEPR model to molecules with double bonds in a virtual laboratory.

7. A. Molecular Structure • The atoms in a molecule have a three dimensional arrangement, • Water - bent LQHS

8. A. Molecular Structure • Linear structure – atoms in a line • Carbon dioxide

9. A. Molecular Structure • Trigonal planar – atoms in a triangle • BF3

10. A. Molecular Structure • Tetrahedral structure • Methane CH4

11. B. The VSEPR Model • Valence shell electron pair repulsion (VSEPR) model • Molecular structure is determined by minimizing repulsions between electron pairs

12. B. The VSEPR Model • 180o - linear • (Note, this is an ionic compound exception AND an octet rule exception!) • Two Pairs of Electrons • BeCl2

13. B. The VSEPR Model • 120o – trigonal planar • Three Pairs of Electrons • BF3

14. B. The VSEPR Model • 109.5o – tetrahedral • Four Pairs of Electrons • CH4

15. B. The VSEPR Model

16. B. The VSEPR Model

17. C. Molecules with Double Bonds • When using VSEPR model to predict molecular geometry of a molecule • a double bond is counted the same as a single electron pair Virtual Lab LQHS