Dalton 's Atomic Theory ( 1803 )

1716 Words May 24th, 2016 7 Pages
Dalton’s atomic theory (1803):
Dalton proposed that all matter is made of atoms (tiny indivisible particles), which cannot be destroyed. He visualised atoms as a solid particle without a structure. All atoms of an element are identical in mass and properties. The atoms of one element differ from the atoms of all other elements in atomic weight. Compounds are combinations of two or more different types of atoms. A chemical reaction results in the rearrangement of atoms in the reactant and product compounds and they don 't destroy or create atoms.
Thomson’s plum pudding model (1909):
Thomson discovered electron in 1897, which allowed him to develop a new atomic model. In Thomson 's model, the atom is composed of electrons surrounded by a positively charged fluid which balances the electrons ' negative charges, like negatively charged "plums" which are surrounded by a positively charged "pudding". Thomson thought the electrons were positioned throughout the atom in rotating rings. The atom was also sometimes described to have a "cloud" of positive charge.
Rutherfordian atomic model (1911):
Rutherford’s discovery of the nucleus allowed him to develop a new atomic model, the planetary model. In this model, the centre of the atom is the nucleus. The nucleus contains most of the mass and all of the positive charge of the atom. Electrons circle around the nucleus like planets do around the sun. Positive protons in nucleus and electrons in orbit around nucleus.
Bohr’s shell…

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