roughly similar affinities for electrons, they will share them rather than gain or lose them entirely In order for sharing to occur, the electron clouds of two atoms must overlap, and this condition results in a fixed arrangement in space between two particular atoms, which thus form a stable combined structure The bonding geometry determines the overall shape of the molecule, and molecular shape in turn defines the ways in which one molecule can react with others The elements most important to life on earth — hydrogen, oxygen, carbon, nitrogen, phosphorus, sulfur — all tend to form covalent bonds, and these make possible the complex, stable assemblages that constitute our bodies and our foods The most familiar pure chemical compounds in the kitchen are water, a covalent combination of two hydrogen atoms and an oxygen; and sucrose, or table sugar, a combination of carbon, oxygen, and hydrogen atoms Covalent bonds are generally strong and stable at room temperature: that is, they’re not broken in significant numbers unless subjected to heat or to reactive chemicals, including enzymes Unlike salt, which dissolves into electrically charged ions, covalently bonded molecules that can dissolve in water generally do so as intact, electrically neutral molecules Weak Bonds Between Polar Molecules: Water A third kind of chemical bond, about a tenth as strong and stable as covalent bonds, is the hydrogen bond The hydrogen bond is one of several “weak” bonds that not form molecules, but make temporary links between different molecules, or between different parts of one large molecule Weak bonds come about because most covalent bonds leave at least a slight electrical imbalance among the participating atoms Consider water, whose chemical formula is H2O The oxygen atom has a greater hunger ... Water A third kind of chemical bond, about a tenth as strong and stable as covalent bonds, is the hydrogen bond The hydrogen bond is one of several “weak” bonds that not form molecules, but make temporary... between different parts of one large molecule Weak bonds come about because most covalent bonds leave at least a slight electrical imbalance among the participating atoms Consider water, whose chemical... charged ions, covalently bonded molecules that can dissolve in water generally do so as intact, electrically neutral molecules Weak Bonds Between Polar Molecules: Water A third kind of chemical bond, about a