Lewis Structure

The structure of molecules, ions, or free radicals which have only electron possible localized written with a formula that shows the location of electrons, and called Lewis structures. This formula shows only valence electrons, both found in the covalent bond that links two atom, or as free electrons. The structure of a molecule must be written with true because the position of the electron can change in a reaction, and it is important to know the initial position of the electron prior to drill down to where berpindahannya. For can write the formula of a molecular electronics properly it is necessary to apply

rules as follows:

1. The total number of valence electrons in the molecules (or ions or free radicals) must be a total skin electron valence atoms that contribute the molecule, coupled with a negative charge or reduced by the charge positive ions. So to H2SO4, there are 2 (one for each hydrogen) 6 (For sulfur) 24 (6 for each oxygen) = 32; while for SO4 =, also the number 32 because each atom contributes 6 plus 2 to negative charge.
2. Having ascertained the number of valence electrons, it is necessary to further determine electrons are found in covalent bonds and which do not used to bind (either in a state pairs, or single). Atoms of the second period elements (B, C, N, O, and F) may have 8 valence electrons, although in some ways the atoms are only has 6 or 7 valence electrons. All the atoms of the second period on top always wanted to have 8 valence electrons. This condition is called the octet, and generally have lower energy.  

          For example:

          There are some exceptions. In the case of O2 molecules, the structure of 7a 
          has an energy that lower than the structure of 7b.

 

          The elements of the third period (Al, Si, P, S, and Cl) can have 10 valence 
          electrons because these elements can use the empty d orbitals. For example: 
          PCl5 and SF6 is a stable compound. In SF6, a single electron s and one 
          electron px promoted from the state of the ground state to an empty orbital,
          and six orbital sp3d2 hybrids produced, and the octahedral vertices.

     3.  Usually need to show a formal charge of each atom. 
          Formal charge = ( ∑ e^- free atomic valence)-(∑e^- free + ½  ∑e^- Bond) 

         The total formal charge on all the atoms in a molecule similar to the charge 

         overall. Examples of electronic structure (electron pair bond given by a line,  

         and free electrons indicated by dots).

          A covalent bond coordination expressed by arrows, and the second Such 
          electrons originating from the same atom, ie, the bond can be viewed as a 
          result of orbital overlap with the orbital electrons fill the two vacant. So 
          trimethylamine oxide will be expressed by the formula:

           For a coordinate covalent bond, the laws that accompany the formal charge
           has been altered so that both apply to the atomic electron donor and recipient 
           atoms. So, nitrogen and oxygen atoms in methylamine oxide does not bear a 
           formal charge.