1. Ch 6 Covalent Compounds
What determines whether two atoms will form a bond?
How can a hydrogen atom, which has one valence electron, bond with chlorine, which has seven valence electrons?
What happens in terms of energy after a hydrogen atom bonds with a chlorine atom?

2. Sharing Electrons
Covalent bonds form when atoms share one or more pairs of electrons
Molecular orbitals are the space that shared electron pairs move within
Energy is released when atoms form a covalent bond

3. Bond Length Potential energy determines bond length
Bond is flexible- atoms vibrate
Bond energy- energy required to break bonds in one mole of compound

5. Electronegativity Electronegativity values used to predict bond type
Non-polar covalent electrons shared equally
Polar covalent not equal electron pair held more closely by one of the atoms

6. Some Electronegativity ValuesH
2.1 Li Be B C N O P
1.0
1.5
2.0
2.5
3.0
6.5
4.0 Na Mg Al Si S Cl
0.9
1.2
1.8 K Ca Br
0.8
2.8

7. Electronegativity
measurement of the attraction of the atom for a shared pair of electrons
used to predict bond type
1.7 or greater = ionic bond
polar covalent bond
0-0.3 covalent bond

8. Bonding between non-metals and non-metals
Bonding between non-metals and non-metals. Therefore all atoms included have fairly high electronegativity and few vacancies in valence energy levels. When they bond, they gain electrons to achieve stable configuration. Hence, electrons are shared.
Sharing produces low energy (stable) electron arrangements

9. Properties Gases, liquids, or solids (made of molecules)
Low melting and boiling points
Poor electrical conductors in all phases
Many soluble in nonpolar liquids but not in water

10. Polar molecule Dipole – partial charges on ends
Greater electronegativity difference produces dipoles
Bond types classified by bond character

12. Ethane – covalent bonding

13. Drawing and Naming molecules
Lewis Dot Structures
Valence electrons as dots
Show model of bonding
H H H H
Cl Cl Cl Cl

14. Draw atoms with their valence electrons only as dots, grouped in four possible pairs around the atom. Fill the four places around the atom as if they were four separate orbitals

15. Now combine atoms together to form molecules by pairing electrons without changing the total number of electrons.
Make an 'octet' around each atom in this way (except Hydrogen which can only support 2 valence electrons

16. Octet rule-
atoms form bonds to achieve a noble gas electron configuration. Each atom wants 8 electrons in its valence orbital
1. How many atoms ?
2. How many valence electrons ?
3. Skeletal structure
4. Where do dots go?

17. Electron dot for water
H2O
H H O
H O H

18. Ionic compounds Electron dot symbols - represent valence electrons around atoms
Na + Cl -> Na+ Cl -

19. Multiple Bonds Double bonds – two shared pairs of electrons O O O O
Triple bonds – three shared pairs of electrons
H C C H H C C H

20. Resonance structures
Any one of two or more different arrangements of atoms in a compound
O S O O S O

21. Naming Covalent Compounds
Prefixes indicate how many atoms are present
Second element ends in - ide
P2 S5
Diphosphorus pentasulfide

22. Prefixes
Mono - 1 Di
Tri - 3
Tetra - 4
Penta - 5

23. Molecular Shapes linear trigonal planar tetrahedral trigonal pyramidal
bent
trigonal bipyramidal
octahedral

24. VSEPR Valence shell electron pair repulsion theory
Predict shape based on Lewis structure
Shapes affect properties

28. Shape Affect Properties are affected
Polarity is affected and polarity affects properties