1. COVALENT BONDS Ch. 8 Study Guide

2. 1. How do you determine the number of valence electrons in an element? 1. Group # = # of valence electrons

3. 2. What is a covalent bond? Atoms held together by sharing electrons

4. 3. Compare and contrast ionic and covalent bonds. Ionic Covalent Prefix naming Share electrons Close electronega -tivity -ide ending Lose or gain electrons octet Large difference in electronegativity

5. 4. Give an example of a molecular formula, perspective drawing, a structural formula, and a ball-and-stick molecular model. Molecular Formula  NH3 (g) Structural Formula Space-filling molecular model Ball-and –stick molecular model Perspective drawing N H H H

6. 5. How does the octet rule apply to covalent bonding? Elements will share electrons in order to have 8 electrons on their outer most energy level.

7. 6. How do electron dot structures represent shared electrons? Each pair of electrons (one from each atom) represents a single bond If 2 electrons are donated by each atom then a double bond is formed. If 3 electrons are donated by each atom then a triple bond is formed. Circles show the electrons being shared

8. 7. Draw the electron dot structure for the following molecules: H 2 0 b. CH 4

9. 8. How do atoms form single, double, and triple covalent bonds? Single bond= one electron from each atom Double bond= two electrons from each atom Triple bond= three electrons from each atom

10. 9. Do all of the electrons in an atom bond with those of another atom? What are the two different pairs called? Not all electrons are involved in a bond  Non-bonding pairs  Bonding paris

11. 10. What is the VSEPR theory? The repulsion between electron pairs causes molecular shapes to adjust so that the valence- electron pairs stay as far apart as possible

12. 11. Apply the VSEPR theory to draw the following molecules geometrically. PF 5 H 2 S HCN

13. 12. Compare and contrast nonpolar and polar bonds. -ide ending Lose or gain electrons polar nonpolar Electrons are pulled toward one element Electrons shared equally Valence electrons CH 4 HCl Pull on electrons

14. 13. What is electronegativity? The ability of an element to attract electrons

15. 14. What is the trend of Electronegativity on the periodic table? Lower left hand corner has the lowest electronegativity Upper right hand corner has the highest electronegativity

16. 15. List 2 ways you can tell if a molecule is polar or nonpolar. Polar molecule has one end that is slightly negative and the other end is slightly positive 0.0-0.4- nonpolar covalent  H-H 0.4-1.0- moderately polar covalent  H-Cl 1.0-2.0- very polar covalent  H-F ≥2.0 Ionic  Na + Cl -

17. 16. Determine whether the following molecules are polar or nonpolar. H2S SO3

18. 17. List the prefixes used for naming covalent compounds. Mono Di Tri Tetra Penta Hexa Hepta Octa

19. 18. Name the following covalent compounds: SCl 4 Si 2 Br 6

20. 19. Write the formula for the following compounds: A. carbon tetrabromide- CBr4 B. diphosphorus trioxide- P2O3

21. 20. Explain how polarity applies to paper chromatography. The more polar the material the more it will travel up the chromatography paper.

22. 21.Explain the term “like dissolves like” A polar solute will dissolve a polar solvent A nonpolar solute will dissolve a polar solvent

23. 22. What is hydrogen bonding? When hydrogen bonds with a very electronegative element it is polar hydrogen will appear positive The hydrogen is then attracted to another molecule that is also polar The hydrogen will bond to the end that appears negative