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Covalent Bonds

Nonpolar. Covalent Bonds. Polar. By: Jerry Gentry. Directory. Covalent Compounds 10/30/09. Carbon Allotropes 11/05/09. Non Tetrahedral Amorphous Carbon. Chlorine. Chloroethyne. Diamond. Methane. water. Graphite. Oxygen. Carbon Dioxide. Fullerene. Dichloromethane.

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Covalent Bonds

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  1. Nonpolar Covalent Bonds Polar By: Jerry Gentry

  2. Directory Covalent Compounds 10/30/09 Carbon Allotropes 11/05/09 Non Tetrahedral Amorphous Carbon Chlorine Chloroethyne Diamond Methane water Graphite Oxygen Carbon Dioxide Fullerene Dichloromethane Questions/ Comments Questions/Comments Directory Continued Macroscopic Observations

  3. Directory Luvs vs. Pampers 11/10/09 Packing Peanuts 11/11/09 Luvs (low-density polyethylene) Biodegradable Corn Starch (Polysaccharide - Amylose) Pampers (high-density polyethylene) Non biodegradable Styrofoam (Polystyrene) Questions/ Comments Questions/ Comments Back to Directory page 1

  4. Dichloromethane CH2Cl2 Cl polar Cl H polar C nonpolar H Dichloromethane is a polar molecule. The C-H bonds because their EN difference is .4 but the C-Cl bonds have an EN difference of .5 so they are polar. Dichloromethane is asymmetrical which in turn makes it polar. The shape of the molecule is tetrahedral. It is made up of one carbon atom, two hydrogen atoms, and two chlorine atoms. Directory The model on the left is the property of chemistry.patent-invent.com and the one on the right was created by yikrazuul on wikimedia.org

  5. Chlorine Cl2 Shared electrons Non shared electron pair Non shared electron pair Both of these models are Chlorine. A chlorine molecule is made up of two chlorine atoms which makes it Cl2. It is a nonpolar molecule since the electronegativity difference is 0. The model on the left is a Lewis Structure and the one on the right is a ball and stick model. Chlorine has a linear shape and is symmetrical. Directory The model on the left is from ibchem .com and the one on the right is the property of turbosquid.com.

  6. Methane CH4 Shared electrons (bond) H H C H Methane is a tetrahedral molecule that is nonpolar. It is made up of four hydrogen atoms and one carbon atom. All four bonds have an electronegativity difference of .4 because carbon is 2.5 and hydrogen is 2.1. The molecule is symmetrical. H Directory The model on the left is the property of tutorvista.com and the model is the property of mindprod.com

  7. Water H2O Unshared electron pair H polar O polar H Shared electrons (bond) Water is an asymmetrical molecule that is polar. It is made of two hydrogen atoms and one oxygen atom which makes it H2O. It has two single polar bonds because oxygen is 3.5 and hydrogen is 2.1 so the electronegativity difference is 1.4. It has a bent shape. Directory The model on the left is the property of tutorvista.com and the model on the right is from openchemistry.com

  8. Oxygen O2 Double bond Unshared electron pair Unshared electron pair O O An oxygen molecule has a linear shape that is symmetrical. It is made up of only two oxygen atoms. Since it’s two of the same atom and they both have an electronegativity of 3.5 their difference is 0. This makes the molecule and bond nonpolar covalent. Notice that this molecule has a double bond between atoms since they both need two extra electrons. Directory The model on the left is the property of ibchem.com and the model on the right is the property of globalwarmingart.com.

  9. CO2 Carbon Dioxide Double bonds C O O Unshared electron pair Unshared electron pair Carbon dioxide is a symmetrical molecule that is linear. It is made up of two oxygen atoms and one carbon atom. It has double bonds between each carbon and oxygen as shown above. The bonds between the atoms are polar because the electronegativity of carbon is 2.5 and oxygen’s is 3.5 so their difference is 1. The molecule as a whole is nonpolar though because it’s symmetrical. Directory The model on the left is from ibchem,com and the model on the right is the property of mindprod.com.

  10. Chloroethyne C2HCl Unshared electron pair H C C Cl C Cl H C Triple bond Chloroethyne is made up of two carbon atoms, one hydrogen atom, and one chlorine atom. It is linear and is asymmetrical, since the ends have different atoms. That’s also makes the molecule polar. Notice that there is a triple bond between the carbons. That triple bond helps add –yne to the name. All of those bonds are nonpolar because it’s the same kind of atom. The bond between hydrogen and carbon is nonpolar because the EN difference is 2.5 – 2.1 which equals .4. The bond between carbon and chlorine is polar because the EN difference is 3.0 – 2.5 which equals .5. Directory

  11. Questions/Comments • When we convert oxygen to carbon dioxide in our bodies through respiration where does the carbon come from and how do the two get bonded? • How do methane and oxygen help fire get bigger? Directory

  12. Macroscopic Observations Materials We used a green ball with one bond attachment to represent a chlorine atom. Chlorine only needs one extra electron to be stable so it has one rod. It’s green because in real life it’s yellowish green. We used green rods to model single bonds. These rods didn’t bend . We used a red ball with two bond attachments to represent an oxygen atom. Oxygen needs two electrons to be stable so it has two rods. It’s red because you need oxygen to help make fire. We used a white ball with one attachment for a hydrogen atom. Hydrogen only needs one electron to be stable so it has one rod. It’s white because that is what it’s like in real life. We used flexible white rods to model double or triple bonds. They bent and made it easy to show multiple bonds. We used a black ball with four attachment rods to represent carbon. Carbon needs four electrons to be stable so it has four rods. It’s black because it makes things like graphite and soot. Directory

  13. Non Tetrahedral Amorphous Carbon Macroscopic Observations • Has a low conductivity • Crumbles easily • When it formed it gave off heat • We made it from sucrose, sulfuric acid, and a little water. • When formed it expanded and smoked • Bad smelling Non tetrahedral amorphous carbon has no shape. That’s what amorphous is(having no shape). It looks like a lump or jungle-like. It is made up of trigonal planar shapes and tetrahedrals which also makes it have no shape. There are more trigonal planar shapes in the amorphous carbon than tetrahedrals. Since it has no shape its density can vary(1.8 -2.2). Notice that the white carbons have four electron clouds or bonds(tetrahedral) while the back carbons have three electron clouds(trigonal planar. Back to Directory

  14. Diamond Macroscopic Observations • Very hard • Shiny(has luster) • Has smooth surfaces, but many of them Picture from wikimedia.org Click on the link below to go to an interactive model of a diamond. Notice that it is made up of only carbon atoms. Diamond is made up of many hexagonal chair-like structures that are connected and all atoms have four single bonds or four sp3 electron clouds. Since they have four bonds or electron clouds that means there are tetrahedrals in it. It can kind of look like honeycomb. You will see that diamond is very dense compared to the other carbon allotropes and it is not a good conductor of electricity(it’s an insulator). Since it’s only made of carbon all bonds are nonpolar. The “World of Molecules” site owns this model. Back to Directory http://www.worldofmolecules.com/interactive_molecules/diamond.htm

  15. Graphite Macroscopic Observations • Shiny(has luster) • Not very strong(runs off on things) • Pretty smooth Click on the link below to go to an interactive model of graphite. Graphite is made up of all carbon atoms and is made up of hexagonal layers. Each layer is made up of many trigonal planar shapes since each carbon has three bonds (two single and one double) or 3 sp2 electron clouds. The layers are off-center and held together with London forces. That is why graphite comes apart easily and goes on things like paper. Graphite is also a good conductor of electricity. The linked model is the property of the worldofmolecules.com website. Back to Directory http://www.worldofmolecules.com/interactive_molecules/diamond.htm

  16. Fullerene Macroscopic Observations • It’s powdery • Grayish or black color • Rubs off on things easily • Feels kind of soft • It varies in conductivity Click on the link below to go to an interactive fullerene model. Fullerene is another carbon allotrope. It is shaped like a soccer ball. The sphere has thirty two faces on it with twenty of them being hexagons and twelve being pentagons. The pentagons help to give it its spherical shape instead of being flat like graphite. Each atom has three bonds(two singles, one double) or three sp2 electron clouds. Since each atom has three electron clouds fullerene is made up of trigonal planar shapes. It has the lowest density of the four carbon allotropes shown and is very soft. The linked model is the property of the worldofmolecules.com website. Back to Directory http://www.worldofmolecules.com/interactive_molecules/fullerene.htm

  17. Questions/Comments • Why are some carbon allotropes clear(diamond) and others are black or gray(graphite and soot)? • What makes the pentagons show up in fullerene and not in the graphite? Back to Directory

  18. Luvs (Low-Density Polyethylene) Macroscopic Observations • Soft • Flexible/stretchy • Melts at 222 F • Recycling code 4 • Bead floated in the water/alcohol mix • Found in things like Gap bags • Bigger bead • Density is 0.92 g/Ml Carbon is the darker balls and hydrogen is the lighter balls. Low-density polyethylene is very branched as seen above. This leaves a lot of open space and makes it less dense than high-density polyethylene. LDPE is made of carbon and hydrogen. Notice that when a row branches off, two carbons are bonded at the start of it. One the carbons hydrogen atoms gets replaced with a carbon and a new link forms. Since it is low density and can’t pack together as well, LDPE has a lower boiling and melting point than HDPE. Back to Directory The model above is the property of chemistryland.com

  19. Pampers (High-Density Polyethylene) Macroscopic Observations • Smaller bead • Had ripples on the diaper material • It broke quicker than Luvs when you tried to stretch it • The bead sank in the water/alcohol mixture • Melting point is 250 F • Recycling code 2 • Found in Fareway bags • Density is 0.95 g/ML High-density polyethylene is linear as shown above. This makes it easier to pack together and make it more dense. It is made up of carbon and hydrogen just like low density polyethylene, but it doesn’t branch out like LDPE does. Since it packs well HDPE has a higher melting and boiling than LDPE. The gray balls above are carbon and the bluish balls are hydrogen. All carbon atoms have four bonds while all hydrogen atoms have one. Back to Directory The model above is the property of the faculty.uscupstate.edu website.

  20. Questions/Comments • What causes some polyethylene to branch off and become LDPE and others to stay linear and form HDPE? • Is there a reason that the LDPE beads were bigger than the HDPE beads? Back to Directory

  21. Corn Starch Peanuts Polysaccharide-Amylose CH2O Macroscopic Observations In water In Acetone • It turned into a white mixture quickly after being submerged in water • It was a thick mixture • It was a bubbly mixture • Felt like marshmallow after being changed • It absorbed a little • It floated • Nothing significant happened Back to Directory Corn Starch Continued

  22. Corn Starch Peanuts Polysaccharide-Amylose CH2O Click on the link below to go to an interactive polysaccharide-amylose model. The polysaccharide-amylose looks more complicated than polystyrene. It is made up of hydrogen, carbon, and oxygen. Each oxygen has two bonds(which makes a bent shape), each hydrogen has one bond(which makes it linear), and each carbon has four bonds(which makes it tetrahedral). Since all of these atoms create different shapes it gives the amylose an interesting shape. It is a pretty straight molecule and doesn’t branch out the way some do. The polysaccharide doesn’t have benzene rings like polystyrene packing peanuts do. Corn Starch packing peanuts are useful because they are biodegradable. It is a polar molecule. http://jchemed.chem.wisc.edu/JCEWWW/Features/MonthlyMolecules/2003/Nov/ Back to Directory Corn Starch Pg. 1 The linked molecule is the property of the jchemed.chem.wisc.edu website.

  23. Styrofoam Peanuts Polystyrene Macroscopic Observations In water In Acetone • It floated • Didn’t absorb water • Just sat there • Dissolved very quickly • Bubbled • Shriveled up • When we mixed what was left of the polystyrene together it was like playdough Styrofoam continued Back to Directory

  24. Styrofoam Peanuts Polystyrene Styrofoam or Polystyrene is non-biodegradable so it is being used less than it used to be since corn starch peanuts have come into play. It is a nonpolar molecule. It’s a relatively simple string of molecules and is made of only carbon and hydrogen. It has benzene rings in place of a hydrogen atom for every other set of CH2. A benzene ring is a hexagon made of carbon and each carbon has a hydrogen bonded to it. Click here for a link to an interactive benzene molecule. Click here for a link to an interactive polystyrene molecule. Benzene ring Back to Directory Styrofoam Pg. 1 The model above is the property of the pslc.ws website The linked models are the property of the interactive library at edinformatics.com

  25. Questions/Comments • What macroscopic differences are there between syndiotactic polystyrene and atactic polystyrene? • Why do corn starch packing peanuts dissolve in water but not in acetone? • Why do polystyrene packing peanuts dissolve in acetone but not in water? Back to Directory

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