1. Introduction to Biochemistry
Chemical Bonds
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So you guys already know that ionic and covalent bonds are types of intramolecular bonds that occur within a molecule. And recall that ionic bonds are interactions between atoms that have opposite charges due to losing and gaining electrons, but not sharing electrons. And recall that covalent bonds occur when 2 atoms share a pair of electrons, and those electrons can either be shared equally or unequally. If the electrons are shared equally between 2 atoms, then this forms a non polar covalent bond, a non polar covalent bond. Whereas, if the electrons are shared unequally, then this forms a polar covalent bond. And what determines the polarity of a of a bond is actually the difference in electronegativity, electronegativity between 2 atoms. And so recall that electro And so, in our example below, we're going to consider the 3 types of bonds. And in the left column, we have ionic bonds. So, we know that ionic bonds do not share electrons, so we can put no in here. And in fact, what they do is they transfer electrons. So there's a transfer of electrons, but no sharing. Now, covalent bonds regardless of the type, we know that there is sharing of electrons, so we can put yes in here. Now, for polar covalent bonds, we know that there is unequal sharing of electrons, whereas for non polar covalent bonds, we know that there is equal there's equal sharing of electrons. Now, for the electronegativity of the atoms, in ionic bonds, the atoms differ greatly in electronegativity, and there's actually a transfer of the electrons. Now, for polar covalent bonds, there's also a significant difference in the electronegativity the And in nonpolar covalent bonds, the atoms have either the same electronegativity or a very, very similar electronegativity. And so for examples, recall that the classic example of an ionic bond is table salt or sodium chloride, where the sodium has one less electron and, the chlorine has one additional electron than proton, and so that gives them their charges. And the the opposite charges is what keeps this molecule, intact or allows them to create an ionic bond. Now over here for polar, we know that water molecules are polar, molecules because they have, an oxygen and hydrogen. Oxygens are super electronegative, whereas hydrogens are not electronegative, not very electronegative, and so oxygens are gonna have a partial negative charge and the hydrogens are gonna have a partial positive charge, and that will occur on both hydrogens. And, over here with this molecule, the carbon dioxide, there's also polar bonds. So you can see the carbon here is gonna have a partial positive charge, whereas the 2 oxygens are gonna have partial negative charges. But because the, polarity is going in opposite directions, so you have electron density being pulled in opposite directions, the overall molecule, even though it contains polar covalent bonds, the overall molecule is non polar. So for a molecule to be considered polar, you also have to consider its shape. And so this is a non polar molecule that contains polar bonds. And then for nonpolar covalent bonds, we have this hydrogen gas molecule where we have 2 hydrogen atoms that have the same electronegativity, and so that creates a, non polar bond where they share electrons equally. So in our next video, we're gonna recap intermolecular bonds. So I'll see you guys in that video.
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