COVALENT BONDS

Covalent clip

I.The Covalent Bond A. Why do atoms form bonds? 1. To get 8 valence shell electrons (noble gas configuration) 2. more stable configuration - less potential energy B. Definition of Covalent Bond 1. bond resulting from sharing electrons 2. share electrons by overlapping of orbitals

I.The Covalent Bond A. Why do atoms form bonds? 1. To get 8 valence shell electrons (noble gas configuration) 2. more stable configuration - less potential energy B. Definition of Covalent Bond 1. bond resulting from sharing electrons 2. share electrons by overlapping of orbitals

II.Heisenberg Uncertainty Principle It is impossible to know exactly the position and velocity of a particle at the same time. The better we know one, the less we know the other. The act of measuring changes the properties. Look at a fan

More obvious with the very small To measure where a electron is, we use light. But the light moves the electron And hitting the electron changes the frequency of the light. Watch the balloon

After Before Photon changes wavelength Photon Electron Changes velocity Moving Electron

Covalent Bonds – Sharing of Electrons

O The Lewis dot structure for Oxygen Oxygen is in group VIA so it has 6 valence electrons

Cl The Lewis dot structure for Chlorine chlorine is in group VIIA so it has 7 valence electrons

Ca The Lewis dot structure for calcium calcium is in group IIA so it has 2 valence electrons

Making calcium chloride + Ca Cl Ca( Cl )2

Lewis dot structure of a compound H NH3 H N H

H O Water - H2O Each hydrogen has 1 valence electron Each hydrogen wants 1 more The oxygen has 6 valence electrons The oxygen wants 2 more They share to make each other happy H O

H O Water Put the pieces together The first hydrogen is happy The oxygen still wants one more H O

H O H Water The second hydrogen attaches Every atom has full energy levels H O H

O2 Oxygen is also one of the diatomic molecules

O How will two oxygen atoms bond?

O Each atom has two unpaired electrons

O

O

O

O

O

O

O Oxygen atoms are highly electronegative. So both atoms want to gain two electrons.

O Oxygen atoms are highly electronegative. So both atoms want to gain two electrons.

O

O O

O O

O O

Both electron pairs are shared.

O O 6 valence electrons plus 2 shared electrons = full octet

O O 6 valence electrons plus 2 shared electrons = full octet

O O two bonding pairs, making a double bond

O O = For convenience, the double bond can be shown as two dashes.

This is the oxygen molecule, = this is so cool!! This is the oxygen molecule, O2

This is the oxygen molecule, = this is so cool!! This is the oxygen molecule, O2

Types of Covalent Bonding Nonpolar Polar

Non polar and Polar Bonds When the atoms in a bond are the same, the electrons are shared equally. This is a nonpolar covalent bond. When two different atoms are connected, the electrons may not be shared equally. This is a polar covalent bond. How do we measure how strong the atoms pull on electrons?

Electronegativity A measure of how strongly the atoms attract electrons in a bond. The bigger the electronegativity difference the more polar the bond. 0.0 - 0.3 Covalent nonpolar 0.3 - 1.7 Covalent polar 1.7> Ionic

Covalent: Non-polar 0>0.3 Polar: 0.3 < 1.7 Ionic > 1.7

Electronegativity A. Nonpolar Covalent Bonds 1. equal sharing of electrons 2. difference in electronegativity is (0 - .3 ) 3. examples ( H2 O2 N2 Cl2)

B. Polar Covalent Bonds 1. unequal sharing of electrons a. electrons spend more time by one of the atoms b. atoms take on a charge (+dipole or - dipole) c. difference in electronegativity is (.3 - 1.7 ) 2. examples (HBr H2S CBr4 )

C. Ionic Nature of Covalent Bonds 1. polar covalent bonds have an ionic nature a. when ionic nature is greater than 50% the bond is considered ionic 1) electronegativity difference is greater than 1.7

3. diatomic molecules (contain two atoms) a. periodic table (1,1-7--->group 17) elements that form diatomic molecules H2 N2 O2 F2 Cl2 Br2 b. compounds can also be diatomic HCl CO NO HF HI HBr

C. Examples and Diagrams H2 F2 HF Make a drawing D. What is a molecule? 1. two or more atoms bonded covalently 2. examples- Make a drawing (usually two or more nonmetals) H2O NH3 CH4 N2O5 HCl C6H12O6

Isomers- Build the molecule On the right using springs for double bonds. Figure 3.32 – Page 312

Use molecular model kit to build 1. PH3 2. H2S 3. HCl 4. CCl4 Lewis structure Use molecular model kit to build 1. PH3 2. H2S 3. HCl 4. CCl4 5. SiH4 6. CH4 7. ClF3 8. PCl5 9. SO2 10. N2O5

Lewis structure 1. PH3 2. H2S 3. HCl 4. CCl4 5. SiH4

ClF3 PCl5 SO2 N2O5