1. Chapter 9 Covalent Bonding

2. A. Covalent Bond – a chemical bond Covalent Bond Covalent Bond resulting from the sharing of valence electrons resulting from the sharing of valence electrons B. Molecule – particle formed when two or more atoms are covalently bonded together C. Lewis Structure

3. D. Sigma Bond 1. Electrons shared along line joining two atoms two atoms 2. All single bonds are sigma bonds 3. 1 bond always consists of two shared electrons electrons E. Multiple bonds can occur when more than one pair of electrons are shared between atoms

4. F. Pi bond – shared pair of electrons is located above and below line joining two atoms G. A double bond consists of one sigma bond and one Pi bond

5. H. The strength of a bond depends upon the bond length. The shorter the bond, the greater the bond strength I. Multiple bonds are shorter and therefore stronger

6. J. The breaking of bonds requires an input of energy K. The formation of bonds releases energy L. In an endothermic reaction the energy required to break the bond is greater than the energy released when new bonds are formed

7. Naming Molecules A. Binary Molecular Compounds 1. Name the first element 2. Use the root of the second element and add ide and add ide 3. Prefixes are used to indicate the number of atoms of each type number of atoms of each type 4. Example P 2 O 5 – diphosphorus pentaoxide pentaoxide

8. B. Binary Acids 1. Use the prefix hydro 2. Follow the root of the second element with the suffix ic and add the word with the suffix ic and add the word acid acid 3. Example – HCl hydrochloric acid

9. C. Oxyacids 1. If the name of the anion ends in – ate, add the suffix –ic to the root of ate, add the suffix –ic to the root of the second element and add the word the second element and add the word acid acid 2. Example – H 2 SO 4 – Sulfuric Acid 3. If the name of the anion ends in –ite, add the suffix –ous and add the word add the suffix –ous and add the word acid H 2 SO 3 – Sulfurous Acid acid H 2 SO 3 – Sulfurous Acid

10. Molecular Structures A. Determining Structural Formula 1. Predict the location of certain atoms a. Hydrogen is always a terminal a. Hydrogen is always a terminal atom atom b. The atom with the lowest b. The atom with the lowest electronegativity is the central electronegativity is the central atom atom

11. 2. Determine the total number of electrons available for bonding electrons available for bonding 3. Divide the number of electrons by 2 4. Place a single bond between the central atom and each terminal atom central atom and each terminal atom 5. Subtract the number of pairs in step 4 from the number of pairs in step 3. Place remaining pairs around the terminal atoms to satisfy the octet rule. Any leftover pairs are placed around the central atom.

12. B. Resonance Structures – more than one valid Lewis structure C. Exceptions to the octet rule D. Coordinate Covalent Bond – both electrons of the bonding pair come from the same atom

13. Resonance

14. Molecular Shape A. Molecular shape determined by VSEPR model 1. Valence Shell Electron Pair Repulsion 2. Arrangement minimizes repulsion of shared and unshared electrons

15. 3. Repulsion between electron pairs a. Unshared – Unshared – greatest b. Unshared – Shared c. Shared – Shared - least B. Hybridization – orbitals mix to form new identical hybrid orbitals

16. Electronegativity & Polarity A. Electronegativity – an atom’s relative attraction for shared electrons B. Electronegativity increases to the right and upward on the periodic table C. Polar Covalent Bond – electron pairs are unevenly shared 1. The greater the difference in electronegativity – the more polar the bond

17. 2. Electronegativity difference greater than 1.7 = ionic bond than 1.7 = ionic bond 3. less than 1.7 = covalent bond D. Polar Molecule 1. Contains polar covalent bonds 2. Asymmetrical shape

19. E. Properties of covalent compounds are determined by intermolecular forces (vand der Waals) 1. Hydgrogen bond – strongest 2. dipole – dipole 3. dipole – nondipole 4. dispersion – nonpolar – nonpolar – weakest weakest 5. The greater the intermolecular force – higher the melting point & boiling point point

20. F. Covalent Network Solid 1. Atoms interconnected by covalent bonds bonds 2. Properties – brittle, extremely hard – example - diamonds example - diamonds