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SZABIST Intermediate College Mirpurkhas The Atomic Structure

PREPARED BY : Muhammad Zia-ulhaque Rathore, Lecturer in Chemistry CHEMISTRY-XI, CHAPTER # 03

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THE ATOMIC STRUCTURE Introduction:In 1808 John Dalton considered that all matter was composed of very small particles called Atom. He visualized theatom as hard solid individual particle incapable of subdivision. Main postulates of Daltons Atomic Theory arefollowing:

1. Matter is composed of very tiny or microscopic particles called "Atom".2. Atom is an indivisible particle.3. Atom can neither be created nor it is destroyed.4. Atoms of an element are identical in size, shape, mass and in other properties.5. Atoms of different elements are different in their properties.6. Atoms combine with each other in small whole numbers.7. All chemical reactions are due to combination or separation of atoms.

Today it is well established that atoms are complex organization of matter and energy. Many particles have been

discovered within the atom. These sub-atomic particles include electron, proton, neutron, positron, neutrino andseveral types of mesons and hyprons etc.Different scientists in this field are as follows:

Faradays experiment indicates the existence of electrons. Crookes tube experiments show the presence of electrons and protons in the atoms. Radioactivity further confirms the presence of electrons and protons. Chadwick experiment shows the presence of neutrons. Spectroscopic experiments reveal the electronic structure of atoms.

Introduction:When electricity passes through electrolytic solution, it decomposed this solution into two negatively and positivelycharged ions. This phenomenon was studied by in greater detail by Faraday. Faradays Law:According to this law:The weights of substances li berated or deposited at electrodes duri ng electrolysis wi ll be according to their equivalents when equal quanti ty of electri city is passed in dif ferent solu ti ons Faradays Experiment:Faraday passed the electricity through the electrolytic solution. He took two metals plates named electrodes, are placed in electrolytic solution and passed. The solution spilt into negative and positive charge particles. The positive charge particles move towards cathode, which is negative electrode and negative charge particles movetowards anodes, which is positively electrode.Faradays also determined the charges of different ions and the amount of elements liberated from electrolyticsolution.Conclusion:He observed that there is some elementary unit of electric charge associated with these ions, which can becalculated. He also proved that electricity just like matter, is atomic in nature F/N is the unit of electric charge for such unit of electric charge, Stoney in 1891 gave the name Electron.

Chapter # 3

FARADAYS EXPERIMENT (Passage of electricity through solution)

(Clue about electrons)

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SZABIST Intermediate College Mirpurkhas The Atomic Structure

PREPARED BY : Muhammad Zia-ulhaque Rathore, Lecturer in Chemistry CHEMISTRY-XI, CHAPTER # 03

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