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Ionic & Molecular Compounds Lewis Dot Structures Susan Baird Dori Delaney Cindy Rothwell.

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Presentation on theme: "Ionic & Molecular Compounds Lewis Dot Structures Susan Baird Dori Delaney Cindy Rothwell."— Presentation transcript:

1 Ionic & Molecular Compounds Lewis Dot Structures Susan Baird Dori Delaney Cindy Rothwell

2 Ionic & Molecular Compounds Lewis Dot Structures Review: Valence electrons are the electrons that are involved in bonding. Return to Home Page

3 Ionic & Molecular Compounds Lewis Dot Structures Review: Valence electrons are the electrons that are involved in bonding. The number of valence electrons in an element is equal to its Main Group number. Return to Home Page

4 Ionic & Molecular Compounds Lewis Dot Structures G. N. Lewis invented a short hand notation for representing the valence electrons in an atom. Lewis represented the valence electrons as dots arranged around the symbol of the element. Return to Home Page

5 Ionic & Molecular Compounds Lewis Dot Structures Instead of representing a Group 7A element such as fluorine like this: Lewis represented F like this: Return to Home Page

6 Ionic & Molecular Compounds Lewis Dot Structures Notice that six of the electrons are arranged in pairs around the central symbol for the element. The 7 th electron is unpaired. Return to Home Page

7 Ionic & Molecular Compounds Lewis Dot Structures Here are some common examples of Lewis Dot Structures of different elements: Return to Home Page

8 Ionic & Molecular Compounds Lewis Dot Structures Notice in the Lewis Dot Structure for carbon, the 4 electrons are arranged around the symbol and none of them are paired. When you fill in the dots around the symbol, you should put one electron on each of the four sides of the symbol before you pair them up. Return to Home Page

9 Ionic & Molecular Compounds Lewis Dot Structures The Lewis Dot Structure of carbon indicates that it needs to form four bonds. For nonmetals the number of bonds an element needs to form is: 8 – Main Group Number Carbon is in Group 4A so for C: 8 – 4 = 4 bonds. Return to Home Page

10 Ionic & Molecular Compounds Lewis Dot Structures Now it’s your turn. Draw Lewis Dot structures for nitrogen and oxygen atoms. How many bonds does each element need to form with another nonmetal? Answers are on the next pages. Return to Home Page

11 Ionic & Molecular Compounds Lewis Dot Structures Examine the structure. N has 3 unpaired electrons so it needs to form 3 bonds. Alternatively N is in Group 5A 8 – 5 = 3 bonds Return to Home Page

12 Ionic & Molecular Compounds Lewis Dot Structures Examine oxygen’s structure. It has two unpaired electrons so it needs to form two bonds with another nonmetal. Alternatively, O is in Group 6A 8 – 6 = 2 bonds Return to Home Page

13 Ionic & Molecular Compounds Lewis Dot Structures This video introduces common bonding patterns represented by Lewis Dot Structures.Lewis Dot Structures Now let’s see how we can use Lewis Dot Structures to represent the oxygen molecule O 2 and the ammonia molecule NH 3.Lewis Dot Structures Return to Home Page

14 Ionic & Molecular Compounds Lewis Dot Structures Now it’s your turn. Draw the Lewis Dot Structure for methane, CH 4. Methane is the major component in natural gas. The answer is on the next page. Return to Home Page

15 Ionic & Molecular Compounds Lewis Dot Structures Notice that the bonding electrons can be represented by dots or more commonly by a line that joins the two atoms. Notice that methane does not contain any nonbonding pairs of electrons. Return to Home Page

16 Ionic & Molecular Compounds Lewis Dot Structures Now try drawing the Lewis Dot structure for hydrogen sulfide, H 2 S. H 2 S is a poisonous gas that smells of rotten eggs. The answer is on the next page. Return to Home Page

17 Ionic & Molecular Compounds Lewis Dot Structures Notice the similarity between the H 2 O molecule and the H 2 S. Both molecules have two nonbonding pairs of electrons and both can be drawn with a bent shape. Both O and S are in Group 6A on the periodic table. Return to Home Page

18 Ionic & Molecular Compounds Lewis Dot Structures Now what happens when we try to draw the Lewis Dot Structure of O 2 ? Return to Home Page

19 Ionic & Molecular Compounds Lewis Dot Structures Now what happens when we try to draw the Lewis Dot Structure of O 2 ? Each Oxygen atom has six valence electrons and needs to form two bonds. Return to Home Page

20 Ionic & Molecular Compounds Lewis Dot Structures Now what happens when we try to draw the Lewis Dot Structure of O 2 ? Each Oxygen atom has six valence electrons and needs to form two bonds. It will have to form two bonds to the other oxygen atom. Return to Home Page

21 Ionic & Molecular Compounds Lewis Dot Structures Notice the double bond between the two oxygen atoms. Return to Home Page

22 Ionic & Molecular Compounds Lewis Dot Structures Try drawing the Lewis Dot Structure of nitrogen, N 2. The answer is on the next page. Return to Home Page

23 Ionic & Molecular Compounds Lewis Dot Structures Notice that each nitrogen atom shares 3 electrons with the other nitrogen atom. When atoms share 3 pairs of electrons they form a triple bond. Return to Home Page

24 Ionic & Molecular Compounds Lewis Dot Structures Now let’s see what happens when we mix different elements together with single, double and triple bonds.single, double and triple bonds Try drawing the Lewis Dot Structures of CHCl 3, HCN, and H 2 O 2 as suggested by the video. Video answers are on the next few pages. Return to Home Page

25 Ionic & Molecular Compounds Lewis Dot Structures Chloroform is a mild anesthetic that was used by the bad guys in old movies when they wanted to knock someone out. Return to Home Page

26 Ionic & Molecular Compounds Lewis Dot Structures Hydrogen cyanide is a poisonous gas that reportedly smells like almonds. Return to Home Page

27 Ionic & Molecular Compounds Lewis Dot Structures Hydrogen peroxide is used to bleach hair. It contains a rare oxygen—oxygen single bond. Return to Home Page

28 Ionic & Molecular Compounds Lewis Dot Structures Ionic Bonds form when oppositely charged ions attract one another. Return to Home Page

29 Ionic & Molecular Compounds Lewis Dot Structures Ionic Bonds form when oppositely charged ions attract one another. The ions are formed when metals and nonmetals lose or gain electrons to empty or fill their valence shells. Return to Home Page

30 Ionic & Molecular Compounds Lewis Dot Structures Ionic Bonds form when oppositely charged ions attract one another. The ions are formed when metals and nonmetals lose or gain electrons to empty or fill their valence shells. Lewis Dot Structures can also be used to illustrate ionic bonds. Return to Home Page

31 Ionic & Molecular Compounds Lewis Dot Structures The element fluorine is in Group 7A and contains 7 valence electrons. Return to Home Page

32 Ionic & Molecular Compounds Lewis Dot Structures The element fluorine is in Group 7A and contains 7 valence electrons. When fluorine forms an ion it gains one electron to fill its valence shell. Return to Home Page

33 Ionic & Molecular Compounds Lewis Dot Structures Notice that Lewis Dot structures for ions are enclosed in square brackets with the ionic charge written as a superscript on the right side. Return to Home Page

34 Ionic & Molecular Compounds Lewis Dot Structures Now it’s your turn. Try drawing the Lewis Dot structure for O 2-. The answer is on the next page. Return to Home Page

35 Ionic & Molecular Compounds Lewis Dot Structures Return to Home Page

36 Ionic & Molecular Compounds Lewis Dot Structures Positively charged ions can be drawn as Lewis Dot structures too. Magnesium is in Group 2A and has 2 valence electrons. Magnesium loses its two valence electrons to empty its valence shell. Return to Home Page

37 Ionic & Molecular Compounds Lewis Dot Structures Return to Home Page

38 Ionic & Molecular Compounds Lewis Dot Structures Now it’s your turn. Draw the Lewis Dot Structure for Li +. The answer is on the next page. Return to Home Page

39 Ionic & Molecular Compounds Lewis Dot Structures Return to Home Page

40 Ionic & Molecular Compounds Lewis Dot Structures Now let’s form some ionic compounds. Recall the ionic compounds contain a metal bonded to a nonmetal. Return to Home Page

41 Ionic & Molecular Compounds Lewis Dot Structures The Lewis Dot Structure for LiF is: Notice that both ions are enclosed in square brackets and there are no electrons showing on Li because its valence shell is empty. Return to Home Page

42 Ionic & Molecular Compounds Lewis Dot Structures The Lewis Dot Structure for lithium oxide, Li 2 O is: Notice that a subscript 2 is required after the lithium ion because there are 2 lithium ions for every oxygen ion. Return to Home Page

43 Ionic & Molecular Compounds Lewis Dot Structures Now it’s your turn. Try drawing the Lewis Dot Structures for magnesium oxide, MgO and for magnesium fluoride, MgF 2. Return to Home Page

44 Ionic & Molecular Compounds Lewis Dot Structures Return to Home Page

45 Ionic & Molecular Compounds Lewis Dot Structures Now you know how to draw Lewis Dot Structures of Ionic and Covalent compounds. You should return to the Home Page to determine what you need to do next for your WebQuest. Home Page


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