1. Covalent Bonding & Polarity Chapter 6.2

2. Chemical Bonding  Ionic Bond – Force that holds cations and anions together and which involves the transfer of electrons.  Occurs between a metal and a nonmetal.

3. Ionic Bonding  Elements achieve stable electron configurations by transferring or sharing electrons between atoms  Transferring Electrons -  Those with <4 valence electrons “LEND” them (Metals)  These elements “lose” valence electrons OR  Those with >4 valence electrons “BORROW” them (Nonmetals)  These elements “gain” electrons

4. Chemical Bonding  What do you think will happen when 2 nonmetals bond?  Will there be a transfer of electrons? Why? FF

5. Covalent Bonding  When two nonmetals meet - one atom is NOT strong enough to take electrons from the other!  So they must share them  Covalent Bond!  Covalent bond - is a chemical bond in which two atoms share one or more pairs of valence electrons.

6. Covalent Bonding  Electrons want to be in pairs – 4 pairs of 2 to fulfill the octet rule.  Paired electrons are ‘happy’!  Unpaired electrons are ‘sad’

7. Paired or Unpaired Unpaired Electron

8. How it Works +

9. F F Outer Level  Still only hold 8!!!!

10.  All 3 figures represent the same thing!  BAR = Bond of shared electrons FF FFFF

11. This illustration shows four ways to represent a covalent bond between two hydrogen atoms. As a space shuttle lifts off, it leaves a water vapor trail. A reaction of hydrogen and oxygen produces the water.

12.  Diatomic means “two atoms”.  Many nonmetal elements are often found as diatomic molecules.  Atoms of same element share bonding electrons equally.  Balanced

13. FFFF OR Single Bond = One Pair of e - Shared Between Two Atoms. Each atom gives one e - to the shared pair

14. Oxygen and Oxygen O O

15. OR Two Pairs of Electrons are Being Shared Each atom gives one e - to each shared pair OO OO

16. CO 2 Since each are sharing two pairs  Double Bond! CO O

17. Nitrogen and Nitrogen N N N

18. OR Three Pairs of Electrons Being Shared NN NN

19. Make a molecule out of Oxygen and two Fluorine

20. F OF Formula: OF 2 OF F

21. Try Carbon and two Oxygen

22. O CO C O O Formula: CO 2

23. Unequal Sharing of Electrons  Diatomic compounds share electrons equally.  Equal forces pulling on the shared electrons  What happens when atoms do NOT share electrons equally?  Unequal forces pulling on the shared electrons

24. Polar Covalent Bond :  Electrons not transferred from one atom to another, but…  Atom with greater attraction for electrons has a partial negative charge  Other atom has a partial positive charge.  Types of atoms determine whether a molecule is polar or non-polar.

25.  Electronegativity = Atom’s attraction for electrons  Bigger value  stronger attraction  Electronegativity trends (attraction for electrons):  Right side of periodic table: high  Exception for noble gases (Group #8A) - none  Left side of periodic table: low  Top of a group: higher  Bottom of a group: lower

28.  Shared electrons in a hydrogen chloride molecule spend less time near the hydrogen atom than near the chlorine atom.

29.  Non-polar covalent  Electronegativity difference is <0.5  Polar covalent  Electronegativity difference is >0.5 and <2.0  Ionic bond  Electronegativity difference is >2.0

30.  Boron and Hydrogen  Electronegativities: B = 2.0 H = 2.1  Difference: 0.1  non-polar covalent  Potassium and Iodine:  Electronegativities: K = 0.8 I = 2.7  Difference: 1.9  polar covalent  Sodium and Chlorine  Electronegativities: Na = 0.9 Cl = 3.0  Difference: 2.1  ionic