So now that we've introduced our first type of covalent bond, the nonpolar covalent bonds in our previous lesson videos, in this video we're going to introduce our second type of covalent bond, the polar covalent bonds. And so recall from our previous lesson videos that the term covalent refers to the sharing of electrons between atoms and so these polar covalent bonds are going to involve the sharing of electrons. Now the term polar specifically refers to unequal and so polar covalent bonds are characterized by unequal sharing of electrons between atoms. Now, the reason that there is unequal sharing of electrons between atoms in these polar covalent bonds is due to different electronegativities of the atoms in a polar covalent bond or in other words, the 2 atoms involved in a polar covalent bond will pull on electrons with different strengths, leading to unequal sharing of those shared electrons. Now, of course, unequal sharing of these negatively charged electrons is going to lead to an unequal distribution of those negatively charged electrons between these atoms and that will lead to partial charges throughout the molecule. Now this symbol that you see right here is the Greek symbol delta which represents partial, and so these are not full charges that we're talking about, these are fractioned or partial charges. And so, you'll see this symbol delta throughout our image down below and you'll also see it in our images moving forward as well. And, so if we take a look at our image down below we'll be able to see 3 different examples of polar covalent bonds. And so our first example is within this molecule called hydrogen chloride whose chemical formula is HCl. One hydrogen atom and one chloride atom. And of course the line between these two atoms represents a covalent bond, a shared pair of electrons and this is specifically a polar covalent bond and that is because this chloride atom has a much higher electronegativity in comparison to the hydrogen atom which means that the Chloride atom pulls on electrons harder and so the shared electrons in this, polar covalent bond will be pulled more towards the chloride atom and, less towards the hydrogen atom. And recall that these electrons are negatively charged and so there will be a partial negative charge on the chloride atom and so we can fill that in here, partial negative charge. And on the hydrogen atom because electrons are being pulled away from it, negatively charged electrons are being pulled away from it, giving up a negative charge will make you more positive and so it will have a partial positive charge. And that's exactly what we see down below. Notice that this shared pair of electrons right here is being shared unequally in this polar covalent bond and so the chloride atom has the partial negative charge because it pulls harder on these electrons and the hydrogen atom is going to have a partial positive charge because it pulls less hard or more weakly on those electrons, and so it does not have those negatively charged electrons as much and gains a partial positive charge. And so you can see how the unequal distribution of these electrons leads to these partial charges. Now in the next example, what we have is water whose chemical formula is of course H2O. We know it has 2 Hydrogen atoms and one oxygen atom and, these lines between the oxygen and the hydrogen represent polar covalent bonds and that is because recall that oxygen is one of the most electronegative atoms that exist and so it pulls on electrons very very hard whereas the hydrogen atoms do not pull very hard on electrons. So these electrons that are being shared are going to be shared unequally leading to these polar covalent bonds. And so, notice that the oxygen atom that pulls harder on electrons is going to have the negatively charged electrons for more time so it gains a partial negative charge. And each of the hydrogen atoms is, going to have the electrons for less time and so they gain a partial positive charge. And so every single water molecule is going to have a partial negative charge on the oxygen and partial positive charges on the hydrogen And so that's something important to keep in mind about water. Now in our last example over here what we have is ammonia whose chemical formula is NH3. So there's 1 nitrogen atom and 3 hydrogen atoms. And again, each of these lines represents a polar covalent bond because nitrogen is much more electronegative than the hydrogen. And so, it pulls on the electrons harder. And so the electrons are going to be pulled towards the nitrogen atom. So it is going to gain a partial negative charge as indicated in our image, and each of the hydrogen atoms is going to have a partial positive charge. And so once again, the main takeaway here is that polar covalent bonds are characterized by unequal sharing of electrons between atoms and, it can lead to these partial charges. Now, if we look at our image on the right hand side over here, notice we have this analogy with 2 people playing the tug of war game pulling on this rope. Now, notice each of these people represents an atom. So we have 1 atom over here and another atom over here. And right in the middle, what we have is the electron. The e with the negative symbol is the electron. And notice that this atom over here is pulling harder on the electrons and so the electron is going to be closer to this atom on the right than it is to the one on the left. And because this electron is negatively charged it gives this atom on the right a partial negative charge whereas the atom on the left is going to have a partial positive charge since it has the electrons, for less time. And so this is an analogy showing you unequal sharing of electrons, So this is hopefully helpful to help you better understand these polar covalent bonds. And so we'll be able to get some practice applying these concepts moving forward, so I'll see you all in our next video.
Table of contents
- 1. Introduction to Biology2h 40m
- 2. Chemistry3h 40m
- 3. Water1h 26m
- 4. Biomolecules2h 23m
- 5. Cell Components2h 26m
- 6. The Membrane2h 31m
- 7. Energy and Metabolism2h 0m
- 8. Respiration2h 40m
- 9. Photosynthesis2h 49m
- 10. Cell Signaling59m
- 11. Cell Division2h 47m
- 12. Meiosis2h 0m
- 13. Mendelian Genetics4h 41m
- Introduction to Mendel's Experiments7m
- Genotype vs. Phenotype17m
- Punnett Squares13m
- Mendel's Experiments26m
- Mendel's Laws18m
- Monohybrid Crosses16m
- Test Crosses14m
- Dihybrid Crosses20m
- Punnett Square Probability26m
- Incomplete Dominance vs. Codominance20m
- Epistasis7m
- Non-Mendelian Genetics12m
- Pedigrees6m
- Autosomal Inheritance21m
- Sex-Linked Inheritance43m
- X-Inactivation9m
- 14. DNA Synthesis2h 27m
- 15. Gene Expression3h 20m
- 16. Regulation of Expression3h 31m
- Introduction to Regulation of Gene Expression13m
- Prokaryotic Gene Regulation via Operons27m
- The Lac Operon21m
- Glucose's Impact on Lac Operon25m
- The Trp Operon20m
- Review of the Lac Operon & Trp Operon11m
- Introduction to Eukaryotic Gene Regulation9m
- Eukaryotic Chromatin Modifications16m
- Eukaryotic Transcriptional Control22m
- Eukaryotic Post-Transcriptional Regulation28m
- Eukaryotic Post-Translational Regulation13m
- 17. Viruses37m
- 18. Biotechnology2h 58m
- 19. Genomics17m
- 20. Development1h 5m
- 21. Evolution3h 1m
- 22. Evolution of Populations3h 52m
- 23. Speciation1h 37m
- 24. History of Life on Earth2h 6m
- 25. Phylogeny2h 31m
- 26. Prokaryotes4h 59m
- 27. Protists1h 12m
- 28. Plants1h 22m
- 29. Fungi36m
- 30. Overview of Animals34m
- 31. Invertebrates1h 2m
- 32. Vertebrates50m
- 33. Plant Anatomy1h 3m
- 34. Vascular Plant Transport2m
- 35. Soil37m
- 36. Plant Reproduction47m
- 37. Plant Sensation and Response1h 9m
- 38. Animal Form and Function1h 19m
- 39. Digestive System10m
- 40. Circulatory System1h 57m
- 41. Immune System1h 12m
- 42. Osmoregulation and Excretion50m
- 43. Endocrine System4m
- 44. Animal Reproduction2m
- 45. Nervous System55m
- 46. Sensory Systems46m
- 47. Muscle Systems23m
- 48. Ecology3h 11m
- Introduction to Ecology20m
- Biogeography14m
- Earth's Climate Patterns50m
- Introduction to Terrestrial Biomes10m
- Terrestrial Biomes: Near Equator13m
- Terrestrial Biomes: Temperate Regions10m
- Terrestrial Biomes: Northern Regions15m
- Introduction to Aquatic Biomes27m
- Freshwater Aquatic Biomes14m
- Marine Aquatic Biomes13m
- 49. Animal Behavior28m
- 50. Population Ecology3h 41m
- Introduction to Population Ecology28m
- Population Sampling Methods23m
- Life History12m
- Population Demography17m
- Factors Limiting Population Growth14m
- Introduction to Population Growth Models22m
- Linear Population Growth6m
- Exponential Population Growth29m
- Logistic Population Growth32m
- r/K Selection10m
- The Human Population22m
- 51. Community Ecology2h 46m
- Introduction to Community Ecology2m
- Introduction to Community Interactions9m
- Community Interactions: Competition (-/-)38m
- Community Interactions: Exploitation (+/-)23m
- Community Interactions: Mutualism (+/+) & Commensalism (+/0)9m
- Community Structure35m
- Community Dynamics26m
- Geographic Impact on Communities21m
- 52. Ecosystems2h 36m
- 53. Conservation Biology24m
2. Chemistry
Covalent Bonds
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