NEET

           Atomic Number, Mass Number and Atomic Species   (1) Atomic number or Nuclear charge             (i) The number of protons present in the nucleus of the atom is called atomic number (Z).             (ii) It was determined by Moseley as,                                            where, \[\nu =X-\]rays frequency                            Z= atomic number of the metal                         \[a\And b\] are constant.             (iii) Atomic number = Number of positive charge on nucleus = Number of protons in nucleus = Number of electrons in nutral atom.             (iv) Two different elements can never have identical atomic number.   (2) Mass number             (i) more...

  Atomic Models and Planck's Quantum Theory   Atomic spectrum - Hydrogen spectrum.   Atomic spectrum   (1) Spectrum is the impression produced on a photographic film when the radiation (s) of particular wavelength (s) is (are) analysed through a prism or diffraction grating. It is of two types, emission and absorption. (2) Emission spectrum : A substance gets excited on heating at a very high temperature or by giving energy and radiations are emitted. These radiations when analysed with the help of spectroscope, spectral lines are obtained. A substance may be excited, by heating at a higher temperature, by passing electric current at a very low pressure in a discharge tube filled with gas and passing electric current into metallic filament.             Emission spectra is of two types, (i) Continuous spectrum : When sunlight is passed through a prism, it gets more...

  Dual Nature of Electron               (1) In 1924, the french physicist, Louis de Broglie suggested that if light has both particle and wave like nature, the similar duality must be true for matter. Thus an electron, behaves both as a material particle and as a wave. (2) This presented a new wave mechanical theory of matter. According to this theory, small particles like electrons when in motion possess wave properties. (3) According to de-broglie, the wavelength associated with a particle of mass \[m,\] moving with velocity \[v\] is given by the relation                                     \[\lambda \,=\,\frac{h}{mv},\]  where h = Planck?s constant. (4) This can be derived as follows according to Planck?s equation,  \[E=\,h\nu =\frac{h.c}{\lambda }\]  more...

  Uncertainty Principle and Schrodinger Wave Equation   Heisenberg’s uncertainty principle.   (1) One of the important consequences of the dual nature of an electron is the uncertainty principle, developed by Warner Heisenberg.               (2) According to uncertainty principle “It is impossible to specify at any given moment both the position and momentum (velocity) of an electron”.               Mathematically it is represented as, \[\Delta x\,.\,\Delta p\ge \frac{h}{4\pi }\]               Where \[\Delta x=\]uncertainty is position of the particle, \[\Delta p=\]uncertainty in the momentum of the particle               Now since \[\Delta p=m\,\Delta v\]               So equation becomes,  \[\Delta x.\,m\Delta v\ge \frac{h}{4\pi }\] or  \[\Delta x\,\times \,\Delta v\ge \frac{h}{4\pi m}\]               The sign \[\ge \] means that the product of \[\Delta x\]and \[\Delta p\](or of \[\Delta x\]and\[\Delta v\]) can be greater than, or equal to but never smaller than \[\frac{h}{4\pi }.\]If more...

Quantum Number, Electronic Configuration and Shape of Orbitals   Quantum numbers and Shapes of orbitals.   Quantum numbers   (1) Each orbital in an atom is specified by a set of three quantum numbers (n, l, m) and each electron is designated by a set of four quantum numbers (n, l, m and s). (2) Principle quantum number (n) (i) It was proposed by Bohr’s and denoted by ‘n’. (ii) It determines the average distance between electron and nucleus, means it is denoted the size of atom. \[r=\frac{{{n}^{2}}}{Z}\times 0.529{\AA}\] (iii) It determine the energy of the electron in an orbit where electron is present. \[E=-\frac{{{Z}^{2}}}{{{n}^{2}}}\times 313.3\,Kcal\,per\,mole\] (iv) The maximum number of an electron in an orbit represented by this quantum number as \[2{{n}^{2}}.\] No energy shell in atoms of known elements possess more than 32 electrons. (v) It gives the information of orbit K, L, M, more...

  Important Terms And Classification Of Animals   Introduction and history of cellular enzymes. Enzymes (Gk. en = in; zyme = yeast) are proteinaceous substances which are capable of catalysing chemical reactions of biological origins without themselves undergoing any change. Enzymes are biocatalysts. An enzyme may be defined as "a protein that enhances the rate of biochemical reactions but does not affect the nature of final product." Like the catalyst the enzymes regulate the speed and specificity of a reaction, but unlike the catalyst they are produced by living cells only. All components of cell including cell wall and cell membrane have enzymes. Every cell produces its own enzymes because they can not move from cell to cell more...

  Classification and factors affecting enzyme Nomenclature and Classification. Dauclax, (1883) introduced the nomenclature of enzyme. Usually enzyme names end in suffix-ase  to the name of substrate e.g. Lactase acts on lactose, maltase act on maltose, amylase on amylose, sucrase on sucrose, protease on proteins, lipase on lipids and cellulase on cellulose. Sometimes arbitrary names are also popular e.g. Pepsin, Trypsin and Ptylin etc. Few names have been assigned as the basis of the source from which they are extracted e.g. Papain from papaya, bromelain from pineapple (family Bromeliaceae). Enzymes can also be named by adding suffix?ase to the nature of chemical reaction also e.g. oxidase, dehydrogenase, catalase, DNA polymerase. (1) According to order classification The older classification of more...

  Important Terms And Classification Of Animals   Outline Classification of Animal kingdom.              The animal kingdom is subdivided into two sub-kingdoms, namely Protozoa and Metazoa.                 Subkingdom 1. Protozoa : It includes microscopic, unicellular animals. It contains a single Phylum called protozoa. more...

  Phylum-Porifera   Phylum Porifera.   (i) Introduction : Lowest multicellular animals or metazoans without true tissues, i.e., at ?Cellular level? of body organization. Familiar as sponges, these animals are well-known for their ability to absorb and withhold fluids. The word ?Porifera? means pore bearers (Gr., porus = pore; ferre = to bear); Their body wall has numerous minute pores, called ostia, through which a continuous current of outside water is drawn into the body. About more...

  Phylum-Coelenterata    Phylum Cnidaria (= Coelenterata). (i) Introduction : ?Tissue grade? eumetazoans with a radial symmetry. The term ?Coelenterata? signifies the presence of a single internal cavity called coelenteron, or gastrovascular cavity, combining functions of both digestive and body cavities. The term ?Cnidaria? indicates the presence of stinging cells (Gr., knide = nittle or stinging cells). About 9,000 species known. (ii) Brief History : more...