1. Chapter 6
Section 1

2. Sharing Electrons
Ionic bond: Electrons transfer from one atom to another to form ions
Covalent bond: Sharing of electrons between atoms
Example: water
O2 + 2H2  2H2O

3. Molecular Orbitals 2 Hydrogen atoms approach each other
The nucleus of each atom attracts its own electron and the electron of the other hydrogen atom
The nucleus repel each other and the electron clouds repel too
There isn’t enough attraction to take electrons away so they share
Form a single electron cloud around by Hydrogen nuclei

4. Molecular Orbitals After they share electrons we have H2
Both Hydrogen atoms are now stable because of the shared electrons
Covalent bond: Forms when two or more valence electrons are shared between atoms

5. Molecular Orbitals Single Bond: Molecular orbital:
Two atoms share one pair of electrons
Molecular orbital:
Space around the two nuclei where shared electrons are moving

6. Covalent Bonds
Nuclei bonded together are not a fixed distance from each other
They vibrate back and forth coming closer and then stretching further apart
Bond length:
The average distance between two bonded atoms

7. Covalent Bonds
Once the nuclei are bonded together are they permanently bonded together?
No!
If the bond energy is reached the bond can break and the two nuclei are no longer bonded
Bond energy:
Energy required to break a bond between two atoms and separate them
Typically stronger bonds the bond length is short
Generally the highest bond energy comes when atoms are bonded to H and F

8. Electronegativity and Bonding
Tendency of an atom to attract bonding electrons to itself when it bonds with another atom
Table 6-2 Electronegativity values
Values generally increase as you go left to right across a period
Down a group values decrease

9. Electronegativity and Bonding
Nonpolar covalent bond:
Bonding electrons are shared equally
H bonded to H
Electronegativities of two atoms are equal
Polar covalent bonds:
2 atoms form a covalent bond but one atom attracts electrons more strongly than the other
Attraction is not strong enough to transfer the electron to the other atom though

10. Electronegativity and Bonding
If the electronegativities are greatly different than an ionic bond forms
Figure 6-7 page 199

11. Determining Ionic or Covalent
The difference between the electronegativities is what is important
Difference greater than 2.1 the bond is ionic
Difference between 0 and .5 the bond is nonpolar covalent
Difference between 0.5 and 2.1 the bond is polar covalent

12. Examples Is the compound AlF3 ionic or covalent
Is the compound AlCl3 ionic or covalent

13. Polar Molecules Polar: Dipole:
Suggests that the ends have opposite charges such as a battery or magnet
Example: HF
F gets the – charge
H gets the + charge
Dipole:
One end has a partial positive charge and the other has a partial negative

14. Dipole Moment
As the polarity of the molecule increases its bond strength also increases
A larger dipole moment indicates a higher degree of polarity