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

Structure Of An Atom

 The term Parmanu was first used by Maharshi Kanad, an Indian saint and philosopher, to describe the unlimited partical of matter. Some western philosophers like Plato, Aristotle, Democritus, Lucretius etc. Also believed that matter is composed of extremely small and indivisible particals called Atoms. Atom is a Greek  word which means indivisible. The origin of idea that matter is composed of small indivisible particals called 'a-tomio' (meaning- indivisible) dates back to the time of Democritus, a Greek philosopher (460-370BC)

       An atom consists of a tiny dence nucleus surrounded by electrons that are spread throughout a relatively large volume of space around the nucleus called an electron cloud. The nucleus contains positively charged protons  and uncharted neutros, so it is positively charged. The elecrons are negatively charged. The amount of positive charge on a proton equals the amount of negative charge on an electron. Therefore, the number of protons and the number of electrons in an uncharted atom must be the same 

       

An atom

    

      Electrons move continuesly. Electron have kinetic energy, and this energy is what counteract the attractive force of positively charged protons otherwise pull the negatively charged electrons into the nucleus. Neutros and protons have approximately the same mass and are about 1800times more massive than electron.most of the mass of an atom, therefore, is in the nucleus. Most of the volume of an atom, however ,is occupied by its electrons.

    The atomic number of an atom is the number of protons in the nucleus. The atomic number is unique to the perticular element.

For example, the atomic number of carbon is 6 which means that all uncharted carbon atoms have six protons and six electrons. Atoms can gain electrons and thereby become negatively charged, lose electrons and becomes positively charged, but the number of protons in an atom of a perticular element never changes. 

  All carbon atoms have the same atomic number, they do not all have the same mass number because they do not all have same number of neutros. The mass number of an atom is the sum of its protons and neutrons, 

        • atomic number = the number of protons in the nucleus

         • mass number = the number of protons +  the number of neutrons

      

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