1. QUANTUM THEORY, also quantum mechanics, in physics, a theory based on using the concept of the quantum unit to describe the dynamic properties of subatomic particles and the interactions of matter and radiation. The foundation was laid by the German physicist Max Planck, who postulated in 1900 that energy can be emitted or absorbed by matter only in small, discrete units called quanta. Also fundamental to the development of quantum mechanics was the uncertainty principle, formulated by the German physicist Werner Heisenberg in 1927, which states that the position and momentum of a subatomic particle cannot be specified simultaneously. 2. Three fundamental particles of matter: A. Proton - a positively charged elementary particle that is a fundamental constituent of all atomic nuclei. A spin of ½, and a mass of 1.673 × 10− 27kg. Symbol: P. B. Neutrons - neutral elementary particle with a rest mass of 1.674 92716 × 10 –27 kilogram and spin 1/2 ; classified as a baryon. In the nucleus of an atom it is stable, but when free it decays. C. Electrons - stable elementary particle present in all atoms, orbiting the nucleus in numbers equal to the atomic number of the element in the neutral atom; a lepton with a negative charge of 1.602 176 462 × 10 –19 coulomb, a rest mass of 9.109 381 88 × 10 –31 kilogram, a radius of 2.817 940 285 × 10 –15 metre, and a spin of 1/2. 3. A. Magnesium no. of protons: 12 no. of neutrons: 12 no. of electrons: 12 B Scandium no. of protons: 21 no. of neutrons: 24 no. of electrons: 21 C Zirconium no. of protons: 40 no. of neutrons: 51 no. of electrons: 40 D Silver no. of protons: 47 no. of neutrons: 61 no. of electrons: 47
Posted on: Thu, 21 Aug 2014 08:42:14 +0000
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