Important Inorganic Molecules

Some Important Inorganic Molecules 
Inorganic molecules are characterized by the presence of a small number of atoms ionically bonded together. In water, however, the atoms are covalently bonded.
Water 
Water is the most abundant molecule in living organ­isms, making up 60-70% of total body weight. Water's physical and chemical properties make life, as we know it, possible.
Sometimes, covalently bonded atoms share electrons unevenly; that is, the electrons spend more time circling the nucleus of one atom than the other. In water, the elec­trons spend more time circulating the larger oxygen (O) atom than the smaller hydrogen (H) atoms. As a result, the hydrogen atoms have a partial positive charge, and the oxy­gen atom has a partial negative charge.

Because the water molecule has charged atoms, it is called a polar molecule. Polar molecules are similar to magnets in that they have positive and negative poles. Hy­drogen bonding occurs between water molecules because they are polar. A hydrogen bond occurs when ­a covalently bonded hydrogen is attracted to a negative charged atom some distance away. The hydrogen bond is represented by a dotted line because the bond is relatively weak and can be broken. Polar molecules ­like water do not form hydrogen bonds with and are unatracted to nonpolar molecules. Some covalent bonds, the electrons are shared unequally, and the result is a polar molecule. Hydrogen bonding can occur between polar molecules.
Caracteristics of Water 
Hyagen bonds cause water molecules to be cohesive-to a together. Without hydrogen bonding between mole­. water would easily boil and easily freeze, making life impossible. Instead, water is a liquid at body temperature. It absorbs a great deal of heat before evaporating and re­this heat as it cools down. This property helps to body temperature within normal limits and even ac­ts for the cooling effect of sweating. The cohesiveness of water also allows it to fill tubular vessels, which makes water an excellent transport medium for distributing subces and heat throughout the body.
Water, being a polar molecule, acts as a solvent and olves various chemical substances, particularly other
ar molecules. This property of water greatly facilitates anical reactions in cells.
Because of hydrogen bonding, water heats up and cools down slowly, and this helps keep body temperature
ithin normal limits. Water is a polar molecule and acts as a solvent; it dissolves various chemical substances and facilitates chemical reactions.
Dissociation
Polarity also causes water molecules to tend to ionize, or .lit up, in the following manner:
H-O-H ----->             H                 +               OH
water                               hydrogen ion                  hydroxide ion  
                
­
The hydrogen ion (H+) has lost an electron; the hydroxide (OH-) has gained the electron. Because very few mol­rules actually dissociate, few H+ and OH- result.

Next: Electrolytes and Acid-Bases                                                     Continue>>