Presentation is loading. Please wait.

Presentation is loading. Please wait.

Part 1:Lewis Dot Diagrams and Structures Lesson 4 – Lewis Diagrams and Molecular Geometry.

Similar presentations


Presentation on theme: "Part 1:Lewis Dot Diagrams and Structures Lesson 4 – Lewis Diagrams and Molecular Geometry."— Presentation transcript:

1

2 Part 1:Lewis Dot Diagrams and Structures Lesson 4 – Lewis Diagrams and Molecular Geometry

3 Review of Chemical Bonds l There are 3 forms of bonding: l _________—complete transfer of 1 or more electrons from one atom to another (one loses, the other gains) forming oppositely charged ions that attract one another l _________—some valence electrons shared between atoms l _________ – holds atoms of a metal together

4 The type of bond can usually be calculated by finding the difference in electronegativity of the two atoms that are going together.

5 Electronegativity Difference l If the difference in electronegativities is between: – ≥ 2.0: Ionic – 0.>0.4 to < 2.0: Polar Covalent – 0.0 to 0.4: Non-Polar Covalent Example: NaCl Na = 0.8, Cl = 3.0 Difference is 2.2, so this is an ionic bond!

6 Review of Valence Electrons Remember from the electron arrangement that valence electrons are the electrons in the OUTERMOST energy level. Remember from the electron arrangement that valence electrons are the electrons in the OUTERMOST energy level. B is 1s 2 2s 2 2p 1 ; so the outer energy level is 2, and there are 2+1 = 3 electrons in level 2. These are the valence electrons! B is 1s 2 2s 2 2p 1 ; so the outer energy level is 2, and there are 2+1 = 3 electrons in level 2. These are the valence electrons! Br is [Ar] 4s 2 3d 10 4p 5 How many valence electrons are present? Br is [Ar] 4s 2 3d 10 4p 5 How many valence electrons are present?

7 Lewis Dot Diagrams l A way of keeping track of valence electrons in ionic compounds. l How to write them? l Write the symbol. l Put one dot for each valence electron l Don’t pair up until they have to (Hund’s rule) X

8 The Lewis Dot diagram for Nitrogen l Nitrogen has 5 valence electrons. l First we write the symbol. N l Then add 1 electron at a time to each side. l Until they are forced to pair up.

9 Lewis Dots For Cations l Metals will have few valence electrons (usually 3 or less) Ca

10 Lewis Dots For Cations l Metals will have few valence electrons l These will come off Ca

11 Lewis Dots For Cations l Metals will have few valence electrons l These will come off l Forming positive ions Ca 2+ Pseudo-noble gas configuration

12 Lewis Dots For Anions l Nonmetals will have many valence electrons (usually 5 or more) l They will gain electrons to fill outer shell. P P 3-

13 Ionic Bonding l Anions and cations are held together by opposite charges. l The bond is formed through the transfer of electrons. l Electrons are transferred to achieve noble gas configuration (octet rule).

14 Lewis Dot Diagrams Ionic Bonding NaCl

15 Lewis Dot Diagrams Ionic Bonding Na + Cl -

16 Lewis Dot Diagrams Ionic Bonding l All the electrons must be accounted for! CaP

17 Lewis Dot Diagrams-Ionic Bonding CaP

18 Lewis Dot Diagrams Ionic Bonding Ca 2+ P

19 Lewis Dot Diagrams Ionic Bonding Ca 2+ P Ca

20 Lewis Dot Diagrams Ionic Bonding Ca 2+ P 3- Ca

21 Lewis Dot Diagrams Ionic Bonding Ca 2+ P 3- Ca P

22 Lewis Dot Diagrams Ionic Bonding Ca 2+ P 3- Ca 2+ P

23 Lewis Dot Diagrams Ionic Bonding Ca 2+ P 3- Ca 2+ P Ca

24 Lewis Dot Diagram Ionic Bonding Ca 2+ P 3- Ca 2+ P Ca

25 Ionic Bonding Ca 2+ P 3- Ca 2+ P 3- Ca 2+

26 Lewis Dot Diagram Ionic Bonding = Ca 3 P 2 Formula Unit

27 Lewis Structures – Covalent Bonding

28 Covalent bonds l Nonmetals hold on to their valence electrons. l Still want noble gas configuration. l By sharing, both atoms get to count the electrons toward a noble gas configuration.

29 Covalent bonding l Fluorine has seven valence electrons F

30 Covalent bonding l Fluorine has seven valence electrons l A second atom also has seven FF

31 Covalent bonding l Fluorine has seven valence electrons l A second atom also has seven l By sharing electrons… FF

32 Covalent bonding l Fluorine has seven valence electrons l A second atom also has seven l By sharing electrons… FF

33 Covalent bonding l Fluorine has seven valence electrons l A second atom also has seven l By sharing electrons… FF

34 Covalent bonding l Fluorine has seven valence electrons l A second atom also has seven l By sharing electrons… FF

35 Covalent bonding l Fluorine has seven valence electrons l A second atom also has seven l By sharing electrons… FF

36 Covalent bonding l Fluorine has seven valence electrons l A second atom also has seven l By sharing electrons… l …both end with full orbitals FF

37 Covalent bonding l Fluorine has seven valence electrons l A second atom also has seven l By sharing electrons… l …both end with full orbitals FF 8 Valence electrons

38 Drawing Lewis Structures l Find total # of valence e -. l Arrange atoms - singular atom is usually in the middle. l Form bonds between atoms (2 e - ). l Distribute remaining e - to give each atom an octet l If there aren’t enough e - to go around, form double or triple bonds.

39 Water H O Each hydrogen has 1 valence Electron (Total of 2e) Each hydrogen wants 1 more The oxygen has 6 valence electrons The oxygen wants 2 more They share to make each other happy

40 Water l Put the pieces together (8 e to distribute). l The first hydrogen is happy l The oxygen still wants one more H O

41 Water l The second hydrogen attaches l Every atom has full energy levels l Remember to check count. H O H

42 Drawing Lewis Structures l CF 4 1 C × 4e - = 4e - 4 F × 7e - = 28e - 32e - F F C F F - 8e - 24e -

43 Drawing Lewis Structures l BeCl 2 1 Be × 2e - = 2e - 2 Cl × 7e - = 14e - 16e - Cl Be Cl - 4e - 12e -

44 Multiple Bonds l Sometimes atoms share more than one pair of valence electrons. l A double bond is when atoms share two pairs (4 total) of electrons l A triple bond is when atoms share three pairs (6 total) of electrons l Know which elements are diatomic (Oxygen?)

45 Carbon dioxide l CO 2 - Carbon is central atom ( more metallic ) l Carbon has 4 valence electrons l Oxygen has 6 valence electrons (total of 12e) l 16e must be distributed. O C

46 Carbon dioxide l Attaching 1 oxygen leaves the oxygen 1 short, and the carbon 3 short O C

47 Carbon dioxide l Attaching the second oxygen leaves both oxygen 1 short and the carbon 2 short l IF the central atom is not surrounded by 4 electron pairs, it does not have an octet. You must convert one or more of the lone pairs on the terminal atoms to a double or triple bonds. O C O

48 Carbon dioxide l The only solution is to share more O C O

49 Carbon dioxide l The only solution is to share more O C O

50 Carbon dioxide l The only solution is to share more O CO

51 Carbon dioxide l The only solution is to share more O CO

52 Carbon dioxide l The only solution is to share more O CO

53 Carbon dioxide l The only solution is to share more O CO

54 Carbon dioxide l The only solution is to share more l Requires two double bonds l Each atom can count all the electrons in the bond O CO

55 Carbon dioxide l The only solution is to share more l Requires two double bonds l Each atom can count all the electrons in the bond l Count e’s O CO 8 valence electrons

56 Carbon dioxide l The only solution is to share more l Requires two double bonds l Each atom can count all the electrons in the bond O CO 8 valence electrons


Download ppt "Part 1:Lewis Dot Diagrams and Structures Lesson 4 – Lewis Diagrams and Molecular Geometry."

Similar presentations


Ads by Google