Chemical Bonds I: Covalent
- 0:15 Valence Electrons
- 1:34 Covalent Bonds
- 3:20 Multiple Bonds
- 4:05 Molecule Structure
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Mom always said that sharing is caring. This lesson will explore how electrons affect the chemical reactivity of atoms and specifically the merits of sharing electrons.
We've talked before about valence electrons and how valence electrons are important in determining the chemical reactivity of different types of atoms. Just as a reminder about atoms that have an incomplete valence shell - for instance, if this is an atom with one electron in its first shell, this atom isn't stable, and it wants to do all it can in order to stabilize its energy. There are basically three different ways that an atom might try to create a full valence level:
1) It could try to add electrons.
2) It could try to give away electrons.
3) It just might decide to share electrons.
This sharing strategy is what we're going to talk about today. When an atom interacts with another atom, it forms what is called a chemical bond. This interaction, this chemical bond links the two atoms together into something called a molecule. Now, we're going to be talking about covalent bonds, which means that the atoms are going to share electrons. Covalent bonds are very strong bonds. They're very important in biology because they're very stable and because most biological molecules are made with covalent bonds. These biological molecules are then very stable.
So, atoms with more than one valence electron - let's take Carbon for example. Carbon has four valence electrons, so it has the opportunity to form four different covalent bonds. So, I can have it bond with hydrogen, and hydrogen will provide one electron of its own. The hydrogens are basically sharing electrons, so it has two valence electrons. And, the carbon atom, instead of having four, now has eight valence electrons. Both the carbon and the hydrogen have stabilized their valence levels by sharing electrons. Instead of a dot representation, the bond between these atoms is often abbreviated with a line. So I can draw the four bonds that carbon can form with these hydrogens like this.
Now, because carbon has four valence electrons, it can form four different bonds. It's possible to form multiple bonds with the same partner atom if that atom also has enough valence electrons for that to happen.
An example of a double bond would be if I have two oxygen atoms. Those two oxygen atoms can share four electrons between the two atoms, forming an oxygen molecule. This is the oxygen that we breathe in the air and which keeps us alive.
By the same token, I can have another kind of bond. We can have a triple bond, and that's three sets of electrons or six electrons being shared between two atoms. Nitrogen gas, that's found in the atmosphere, is a molecule in which two nitrogen atoms are triple bonded together.
One final thing that's nice about covalent bonds in particular is that you can make some predictions about how the molecule will look. The bond length is predictable, so the distance between these two atoms is always going to be the same as long as it's these two atoms. The angle at which the bonds occurs is always the same. If we take a water molecule, for instance, that molecule is H2O, the angle that we find between these two bonds is always going to be the same.
We've learned a little bit about chemical bonding today and specifically about covalent bonds. We've learned that atoms are most stable when they have a full valence level, so atoms that don't have that full valence level are always trying to achieve that state by adding, subtracting or sharing electrons.
When these strategies are employed, the atoms become linked by a chemical bond. These atoms that are linked by a chemical bond form what is called a molecule. We've talked about one of the ways that atoms can bond together and that's through a covalent bond in which electrons are shared between the two atoms. Covalent bonds are very strong and very stable, and we'll find out later how that's important in biology.
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Chapters in Biology 101: Intro to Biology
- 1. Science Basics (6 lessons)
- 2. Review of Inorganic Chemistry For Biologists (14 lessons)
- 3. Introduction to Organic Chemistry (7 lessons)
- 4. Nucleic Acids: DNA and RNA (4 lessons)
- 5. Enzymatic Biochemistry (4 lessons)
- 6. Cell Biology (14 lessons)
- 7. DNA Replication: Processes and Steps (5 lessons)
- 8. The Transcription and Translation Process (10 lessons)
- 9. Genetic Mutations (4 lessons)
- 10. Metabolic Biochemistry (9 lessons)
- 11. Cell Division (13 lessons)
- 12. Plant Biology (12 lessons)
- 13. Plant Reproduction and Growth (10 lessons)
- 14. Physiology I: The Circulatory, Respiratory, Digestive,... (12 lessons)
- 15. Physiology II: The Nervous, Immune, and Endocrine Systems (13 lessons)
- 16. Animal Reproduction and Development (12 lessons)
- 17. Genetics: Principles of Heredity (10 lessons)
- 18. Principles of Ecology (18 lessons)
- 19. Principles of Evolution (9 lessons)
- 20. The Origin and History of Life On Earth (4 lessons)
- 21. Phylogeny and the Classification of Organisms (6 lessons)
- 22. Social Biology (6 lessons)
- 23. Basic Molecular Biology Laboratory Techniques (13 lessons)
- 24. Analyzing Scientific Data (3 lessons)
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