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ATOM IN MODERN SCIENCE
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STRUCTURE OF ATOMS
The first real step forward in an understanding of the various chemical and physical properties of different items was taken when it was accepted that atoms were not simple indivisible particles of various shapes and sizes, but on the contrary rather complex mechanisms with a number of independent parts in motion
In 1904 famous British Physicist JJ Thomson successfully proved that the atoms of various chemi. cal elements consist of positively and negatively charged components They are held together by the forces of electric attraction He called the negatively charged particles Electrons a large number of which were floating in the interior of a mass with a uniformly distributed positive charge The atom on the whole is electrically neutral because the total charge of all negative particles equals the total positive charge The electrons were assumed to be bound comparatively loosely to the body of the atom and one or several of them could be removed by the process of ionisation Thomson was able to estimate 100 FERMIUM
Fm 101 MENDELEYIUM
Md 102 NOBELIUM
No 103 LAWRENCIUM
Lu Lawrencium was discovered at the Universny of California in early 1961 The above elements together with the following natural elements are called actinide elements or elements of acunium senes Atomic No Name
Symbol 89 ACTINIUM
Ac THORIUM PROCTACTINIUM
Po URANIUM
Th
