How The Electrons In An Atom Are Distributed

    Elecrons were perceived to the particals immesurable "planets" that orbit the nucleus of an atom. In 1924, however a French physicist named Louis de Broglie  showed that electrons also have wavelike properties. He did this by combining a formula developed by Albert Einstein 

 that relates mass and energy with a formula developed by Max Planck  that relates Frequency and energy. The realization that electrons have wavelike properties spurred physicist to propose a mathematical concepts know as Quantum mechanics.

    Quantum mechanics uses the same mathematical equations that distribe the wave motion of a guitar string to characterize the motion of an electron around a nucleus. The version of quantum mechanics most useful to chemist was proposed by Erwin Schrodinger in 1926.

     According to Schrodinger, the elecrons in an atom can be thought of an occupying a set of concentric shells that surround the nucleus. The first shell is the one closest to the nucleus. The second shell lies farther from the nucleus. The third and higher numbered shell lie ever farther out 

   Each shell contain subshell known as atomic orbitals. Each atomic orbital has a characteristic shape and energy and occupies a characteristic volume of space.

    The first shell consists only of an s atomic orbital; the second shell consists of s and p atomic orbitals; the third shell consists of s,p, and d atomic orbitals; and the fourth and higher shells consist of s,p,d, and f atomic orbitals.

             

                    

.         Distribution of electrons in the first

            Four shell that surround the nucleus