Page 1 : Energy absorbed, $, , , , , , Increase, in eneray, , Nucleus., , , , Energy emitted, , Decrease, in eneray, , Electron’s energy change, orbits are called stationa, , Designation of energy levels (or orbits), (iii) The energies of permissible orbits are fixed and therefore these, , states or energy level or shells., , L.M,N, O, Bete. The K orbit is, he second orbit (1 = 2), , , , English letters K, , Energy levels or shells are designated by, he first orbit (n = 1); List, , nearest to the nucleus and therefore itis J, the third orbit (n = 3) is M and so on., , , , level (or shell) it does not loose, , neicoostane ina) axeciorbitguaegss '” f, , (jv) As long as the electron revolves in its discrete fixed energy, , energy. Thus, the energy of an electron remai, , different orbits have different energies:, ‘orbit to another, , shen an electron moves from one, , (o) Energy is emitted or absorbed by an atom only wi, en in the chapter, Q.5. Compare all the proposed models of an atom giv, , , , Ans., Thomson's Model Rutherford’s Model Bohr’s Model, , , , ‘According to this model, (j) Electrons revolve around the, nucleus in circular orbits, , ‘According to this model: ‘According to this model:, @ Anatom consists_of_a] () There is positively charged, positively charged sphere centre in an atom called, and electrons are embedded | embedded Sucleus. Neatly all of thel| (ji) The electrons revolve anh, in that sphere. mass of an atom resides in th centain special orbits, the nucleus. called discrete orbits., , (ii) The positive and negative, eiarges (are. equal Timm @D INE Warten revolve | Gi) The energies of “discrete, magnitude hence, the atom around the nucleus in well- ibis are fixed and, as a whole is electrically defined circular orbits. therefore these are called, neutral. ii) The ‘size of the nucleus is stationary states or ene, very small relative to the size Jevels or shells. Energy levels, of the atom. or shells are designated, by K, L M, N, ete. or the, numbers, n = 1,2,3,4, ete, , (wu) As long as the electron, revolves in its discrete fixed, energy level (or shell) it does, not lose energy:, , (v) Energy is emitted 0!, absorbed by an atom only, when an electron moves, from one orbit to another, , , , , , , , , , , , , , , , , , , , L, ). 6. Summarise the rules for writing of distribution of electrons in various shells for the first, , eighteen elements., ans. ‘The distribution of electrons in various shells, the electronic configuration of an element, one sh, , of an atom is called electronic configuration, , In order to write ould proceed as follows:, , d J 66