AIM: HOW TO FORM COVALENT BONDS

Transcription

1 AIM: HOW TO FORM COVALENT BONDS DO NOW: EXPLAIN THE DIFFERENCE BETWEEN IONIC BONDING AND COVALENT BONDS. INCLUDE HOW THE PROPERTIES DIFFER IN SALTS AND MOLECULES, AND WHICH ELEMENTS ARE INVOLVED IN EACH TYPE OF BONDING.

2 OCTET RULE IN COVALENT BONDING In covalent bonding Atoms usually acquire a total of eight electrons, or an octet, by sharing electrons.

3 SINGLE COVALENT BOND A Single Covalent Bond consists of two atoms held together by sharing 1 pair of electrons (2 e - )

4 ELECTRON DOT STRUCTURE

5 SHARED VERSUS UNSHARED ELECTRONS A Shared Pair is a pair of valence electrons that is shared between atoms An Unshared Pair is a pair of valence electrons that is not shared between atoms

6 Chlorine forms a covalent bond with itself Cl 2

7 Cl Cl How will two chlorine atoms react?

8 Cl Cl Each chlorine atom wants to gain one electron to achieve an octet

9 Cl Cl Neither atom will give up an electron chlorine is highly electronegative. What s the solution what can they do to achieve an octet?

10 Cl Cl

11 Cl Cl

12 Cl Cl

13 Cl Cl

14 Cl Cl octet

15 Cl Cl octet circle the electrons for each atom that completes their octets

16 Cl Cl The octet is achieved by each atom sharing the electron pair in the middle circle the electrons for each atom that completes their octets

17 Cl Cl The octet is achieved by each atom sharing the electron pair in the middle circle the electrons for each atom that completes their octets

18 Cl Cl This is the bonding pair circle the electrons for each atom that completes their octets

19 Cl Cl It is a single bonding pair circle the electrons for each atom that completes their octets

20 Cl Cl It is called a SINGLE BOND circle the electrons for each atom that completes their octets

21 Cl Cl Single bonds are abbreviated with a dash circle the electrons for each atom that completes their octets

22 Cl Cl This is the chlorine molecule, Cl 2 circle the electrons for each atom that completes their octets

23 COVALENT BONDING IN H 2 Two hydrogen atoms, each with 1 electron, H.. H can share those electrons in a covalent bond. H: H Sharing the electron pair gives each hydrogen an electron configuration analogous to helium.

24 COVALENT BONDING IN F 2 Two fluorine atoms, each with 7 valence electrons,.... F.... :.. F: can share those electrons in a covalent bond..... :.. F:.. F: Sharing the electron pair gives each fluorine an electron configuration analogous to neon.

25 THE OCTET RULE In forming compounds, atoms gain, lose, or share electrons to give a stable electron configuration characterized by 8 valence electrons..... :.. F:.. F: The octet rule is the most useful in cases involving covalent bonds to C, N, O, and F.

26 Example Combine carbon (4 valence electrons) and four fluorines (7 valence electrons each).. C.. :.... F. to write a Lewis structure for CF :.. F:.. :.. F: C.. :.. F: :.. F: The octet rule is satisfied for carbon and each fluorine.

27 Example It is common practice to represent a covalent bond by a line. We can rewrite.... :.. F:.. :.. F: C.. :.. F: :.. F: as.. : F:.... :.. F C.. F: :.. F:

28 PRACTICE LEWIS DOT STRUCTURES Chemical Formula # of Valence Electrons # of Shared Electrons # of Remaining Electrons Lewis Dot Structure Octet Check All Atoms=8 Hydrogen=2 F 2 H 2 O NH 3 CH 4

29 DOUBLE COVALENT BONDS Sometimes atoms attain noble gas configuration by sharing 2 or 3 pairs of electrons A Double Covalent Bond is a bond that involves 2 shared pairs of electrons (4 e - )

30 O2 Oxygen is also one of the diatomic molecules

31 O O How will two oxygen atoms bond?

32 O O Each atom has two unpaired electrons

33 O O

34 O O

35 O O

36 O O

37 O O

38 O O

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

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

41 O O

42 O O

43 O O

44 O O

45 O O Both electron pairs are shared.

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

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

48 O O two bonding pairs, making a double bond

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

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

51 TRIPLE COVALENT BOND A Triple Covalent Bond is a bond that involves 3 shared pairs of electrons (6 e - )

52 COVALENT BONDS

53 PRACTICE LEWIS DOT STRUCTURE Chemical Formula # of Valence Electrons # of Shared Electrons # of Remaining Electrons Lewis Dot Structure Octet Check All Atoms=8 Hydrogen=2 O 2 CO 2 N 2 HCN