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Elementary Science Education

Covalent Bonding

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      Bernard Nebel

       The following is to enable kids to interpret the structures of molecules as we see them written in “stick and ball” diagrams. To not overwhelm kids with complexity, I have omitted the theory behind why certain atoms form covalent bonds as they do. If you wish to go into this, google: what are covalent bonds video/.

      The basic aspect of covalent bonding is: some elements neither give up an electron nor accept an additional election but rather share a pair of elections, one electron from each of the atoms. This sharing a pair of electrons holds the atoms together in what is called a covalent bond. It is, relatively speaking, a very strong bond, and it has a directional component giving the resulting molecule(s) a particular shape. 

      Only a relatively few elements will form covalent bonds. Most significant are carbon (C), hydrogen (H), oxygen (O), nitrogen (N), and phosphorus (P). These five elements make up the bulk of all molecules of living organisms including humans. 

      The number of covalent bods an element forms is vary specific. H forms one, oxygen two, nitrogen 3, carbon 4, and phosphorus 3 to 5. 

      Covalent bonds between atoms are shown by a simple line between them. Emphasize that line indicates a pair of electrons, one form each atom. For example: Hydrogen gas, H2 is shown as    H — H. Oxygen gas, O2, is  O = O,  showing that the oxygen atoms share two pairs of electrons. 


      Water, H2O, is drawn as      H    H                                                                                                                                       .                                                   \   /                                                                                                                                                 .                                                     O

      Note how the diagrams shows that each H shares one pair and the O shares two pairs of electrons, and there is the directional component.   

      Carbon atoms have four electrons to share, hence will form four covalent bonds


                    — C —   


      Carbon dioxide (CO2) is    O = C = O. 

      Most importantly, the covalent bonding capacity of carbon enables it to form chains, branched chains, and rings, thus making an infinite variety of molecules possible. These are the basis of all living organisms. A relatively simple but very important molecule is the simple sugar, glucose shown below. Examine the molecule and confirm that each atom (C, H, O,) has its requisite number of covalent bonds: C four, O two, and H one.

        Look at the molecular structures of other molecules as you see fit. Type into your browser: molecular structure of _________ image/. In viewing such diagrams of molecules recognize that for simplicity the carbon atoms at the “joints” are often not shown.

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