Covalent bonding

1. Covalent bonding

2. + + How does H2 form? • The nuclei repel

3. + + How does H2 form? • The nuclei repel • But they are attracted to electrons • The hydrogen atoms share the electrons

4. Covalent bonds • Nonmetals hold onto their valence electrons. • They can’t give away electrons to bond. • But the atoms still want noble gas configuration • Nonmetals get a noble gas configuration by sharing valence electrons with each other. • By sharing both atoms count the shared electrons toward noble gas configuration.

5. F Covalent bonding • Fluorine has seven valence electrons

6. F F Covalent bonding • Fluorine has seven valence electrons • A second atom also has seven

7. F F Covalent bonding • Fluorine has seven valence electrons • A second atom also has seven • By sharing electrons

8. F F Covalent bonding • Fluorine has seven valence electrons • A second atom also has seven • By sharing electrons

9. F F Covalent bonding • Fluorine has seven valence electrons • A second atom also has seven • By sharing electrons

10. F F Covalent bonding • Fluorine has seven valence electrons • A second atom also has seven • By sharing electrons

11. F F Covalent bonding • Fluorine has seven valence electrons • A second atom also has seven • By sharing electrons

12. F F Covalent bonding • Fluorine has seven valence electrons • A second atom also has seven • By sharing electrons • Both end with full orbitals

13. Covalent bonding • Fluorine has seven valence electrons • A second atom also has seven • By sharing electrons • Both end with full orbitals F F 8 Valence electrons

14. Covalent bonding • Fluorine has seven valence electrons • A second atom also has seven • By sharing electrons • Both end with full orbitals F F 8 Valence electrons

15. F F Covalent bonding • Fluorine has seven valence electrons • A second atom also has seven • By sharing electrons • Both end with full orbitals • Instead of dots, we use a “–” for the bond

16. Single Covalent Bond • The sharing of two valence electrons. • Only nonmetals and metalloids form covalent bonds • Do not forget about Hydrogen! • Different from an ionic bond because they actually form molecules. • Ionic bonds are a matrix of ions • In an ionic solid you can’t tell which atom the electrons moved from or to.

17. How to show how they formed • I have to tell you what the final formula is or you cannot write the structure • Ionic compounds you can write the formula based on charges • You put the pieces together to end up with the right formula. • For example- show how water is formed with covalent bonds.

18. H O Water 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 satisfy the octet

19. O Water • Put the pieces together • The first hydrogen is good • The oxygen still wants one more electron H

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

21. Water • The second hydrogen attaches • Every atom has full energy levels • Change the dots to lines H O H

22. Multiple Bonds • Sometimes atoms share more than one pair of valence electrons. • A double bond is when atoms share two pair (4) of electrons. • A triple bond is when atoms share three pair (6) of electrons.

23. O Carbon dioxide • CO2- Carbon is central atom • Assume the first atom is central • Carbon has 4 valence electrons • Carbon wants 4 more • Oxygen has 6 valence electrons • Oxygen wants 2 more C

24. O Carbon dioxide • Attaching 1 oxygen leaves the oxygen 1 short and the carbon 3 short C

25. O O Carbon dioxide • Attaching the second oxygen leaves both oxygen 1 short and the carbon 2 short C

26. O O Carbon dioxide • The only solution is to share more C

27. O O Carbon dioxide • The only solution is to share more C

28. O Carbon dioxide • The only solution is to share more O C

29. O Carbon dioxide • The only solution is to share more O C

30. O Carbon dioxide • The only solution is to share more O C

31. Carbon dioxide • The only solution is to share more O C O

32. Carbon dioxide • The only solution is to share more • Requires two double bonds • Each atom gets to count all the atoms in the bond O C O

33. Carbon dioxide • The only solution is to share more • Requires two double bonds • Each atom gets to count all the atoms in the bond 8 valence electrons O C O

34. Carbon dioxide • The only solution is to share more • Requires two double bonds • Each atom gets to count all the atoms in the bond 8 valence electrons O C O

35. Carbon dioxide • The only solution is to share more • Requires two double bonds • Each atom gets to count all the atoms in the bond 8 valence electrons O C O

36. How to draw them • Add up all the valence electrons. (to keep track) • Draw the central atom (or connect multiple central atoms by single bonds) • Connect the outer atoms to the central atom using a single bond • Complete the octet of the outer atoms • Place all extra electrons on the central atom(s) • Complete the octet of the central atom by making multiple bonds

37. Practice • NH3 • H2O • HCN • H2CO • C5H10 (multiple possible structures)

38. Structural Examples H C N H C O H

39. What about resonance? • Resonance is when you can create more than one structure that “appear” to be the same • Only the position of the number of bonds connecting atoms is switched. • But all the bonds must originate from the same central atom • Draw O3

40. What about Exceptions to the Octet? • Sometimes a central atom will not complete an octet • Draw BF3 • Sometimes the central atom will need to have more than an octet to satisfy the octet of the other atoms. • Draw XeF4

41. What about ions? • When drawing a polyatomic ion, you will need to add or subtract the appropriate number of electrons. • Draw NH4+ • Draw CO-2 • Draw OH-