for electrons than the two hydrogen atoms, and so the shared electrons are held closer to the oxygen than to the hydrogens As a result, there’s an overall negative charge in the vicinity of the oxygen, and an overall positive charge around the hydrogen atoms This unequal distribution of charge, together with the geometry of the covalent bonds, results in a molecule with a positive end and a negative end Such a molecule is called polar because it has two separate centers, or poles, of charge A hydrogen bond results from the attraction between oppositely charged ends of polar molecules (or portions of molecules) This kind of bond is important because it’s very common in materials that contain water, because it brings different kinds of molecules into close association, and because it’s weak enough that these molecular associations can change rapidly at room temperature Many of the chemical interactions in plant and animal cells occur via hydrogen bonds Very Weak Bonds Between Nonpolar Molecules: Fats and Oils A fourth kind of chemical bond is very weak indeed, between a hundredth and a ten-thousandth as strong as a molecule-making covalent bond These van der Waals bonds, named after the Dutch chemist who first described them, are the kind of flickering electrical attraction that even nonpolar molecules can feel for each other, thanks to brief fluctuations in their structures Where electrically polar water is held together as a liquid by hydrogen bonds, nonpolar fat molecules are held together as a liquid and given their appealingly thick consistency by van der Waals bonds Though these bonds are indeed weak, their effect can add up to a significant force: fat molecules are long chains and include dozens of carbon atoms, so each fat molecule can interact with many ... chemical bond is very weak indeed, between a hundredth and a ten-thousandth as strong as a molecule-making covalent bond These van der Waals bonds, named after the Dutch chemist who first described them, are the kind of flickering electrical.. .the chemical interactions in plant and animal cells occur via hydrogen bonds Very Weak Bonds Between Nonpolar Molecules: Fats and Oils A fourth kind of chemical bond is very weak indeed, between a... together as a liquid and given their appealingly thick consistency by van der Waals bonds Though these bonds are indeed weak, their effect can add up to a significant force: fat molecules are long