![]() ![]() Individual atoms are very small, and the largest atoms have an approximate diameter of about 5.4 x 10 x 10 m. We define an atom as the smallest part of an element that maintains its identity.Ītoms are particles that cannot be split into smaller particles, and they consist of various subatomic particles. The first Proponents of Atomic Theory were the Greek philosophers Leucippus and Democritus, who proposed in the fifth century BC the following model : Modern atomic theory was first proposed in 1803 by the English chemist John Dalton, whose basic concept states that all elements consist of atoms. The concept of atoms, broadly accepted by Western scientists between the 16th and 19th centuries, was conceived by Greek philosophers in the 5th century BC. ![]() The Greek word atomon (atoms) means "indivisible," and the two philosophers believed that atoms cannot be broken into small pieces. The idea of the atom was infected in the fifth century BC by two Greek philosophers, Democritus and Leukippus. We know that atoms consist of a positively charged nucleus in the center, surrounded by negatively charged electrons. In Dalton's Model of the Atoms (ESAOA), he suggested that all matter consists of small things he called atoms. From the concept of orbitals, one explains molecular structure, chemical bonding, hybridization etc and also things like spectrum of various materials.Democritus, a Greek philosopher who lived in the fifth century BC, theorized about atoms and the specific materials they are made of. Only when the idea of electrons as particles in atoms was introduced, attempts were made to understand chemical bonding and other physical and chemical properties.Īs of now, the electron cloud model which incorporates the principles of quantum mechanics is the most successful. These models were used to explain and hence to understand properties of matter. It was soon realized that the model was flawed and soon Bohr put up his model in which he used Quantum concepts of Planck and Einstein to explain stability of matter and the Hydrogen spectrum.Īnd they process continued when Sommerfeld proposed his model. In his model, he took the electrons embedded into the positive sphere because he found that these electrons (not some positively charged particle) were emitted by a vast range of marerials.įurther, when Lord Rutherford discovered that the positive charge and most of the mass was concentrated in a small region called the nucleus, the proposed his model based on what evidence was available at that time on properties of atoms. However, they should be able to explain the basic properties of matter.įor example, when the electron was first discovered, then JJ Thompson proposed the plum cake model in which he took into consideration the two main points -ġ) From the CRT experiments, it was clear that all matter had those electrons within then thus it would be logical to suppose that electrons were a part of atoms.Ģ) In order to explain the charge neutrality, he supposed that the sphere in which electrons are embedded is positively charged. Such models would be purely theoretical constructs. When the exact structure of the atom remained quite unknown, models were proposed based on experimental evidence of the properties of matter. An atomic model is a theory trying to explain the structure of the atom. ![]()
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