Basic chemistry

 Modern Periodic table Modern Periodic Law :  The recent work has established that the fundamental property of an atom is atomic number and not atomic weight. Therefore, atomic number is taken as the basis of the classification of the elements. The modern periodic law was given by Moseley, it may be stated as : ''The properties of elements are periodic functions of their atomic number". Modern periodic table is also called long form of the periodic table or Bohr’s table. In this table, the elements are arranged in order of their increasing atomic number. It consists of 4 blocks (s, p, d and f), 18 groups numbered from 1 to 18 and 7 periods numbered from 1 to 7. Short tricks to learn periodic table  Blocks : The periodic table is divided into four main blocks (s, p, d and f) depending upon the subshell to which the valence electron enters into.  (1) Elements of group 1 and 2 constitute s-Block.   (2) Elements of group 13, 14, 15, 16, 17, 18 constitute p-Block.   (3)

  Atomic number, Mass number and Atomic species 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,  V 1/2  =a(z-b) Where, v=X -  ray’s frequency  Z= atomic number of the metal a & 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.  Mass number  Mass number (A) = Number of protons or Atomic number (Z) + Number of neutrons or Number of neutrons = A – Z .  (i) Since mass of a proton or a neutron is not a whole number (on atomic weight scale), weight is not necessarily a whole number.  (ii) The atom of an element X having mass number (A) and atomic number (Z) may be represented by a symbol,  Z X A Different types of atomic species Isotopes Given by Soddy 1.They are the atoms of a given element  which have the s

INSIDE THE ATOM   John Dalton 1808, believed that matter is made up of extremely minute indivisible particles, called atom which can takes part in chemical reactions. These can neither be created nor be destroyed. However, modern researches have conclusively proved that atom is no longer an indivisible particle. Modern structure of atom is based on Rutherford’s scattering experiment on atoms and on the concepts of quantization of energy. Composition of atom It is now believed that the atom consists of several sub-atomic particles like electron, proton, neutron, positron, neutrino, meson etc. Out of these particles, the electron, proton and the neutron are called fundamental subatomic particles and others are non-fundamental particles. Fundamental subatomic particles in an atom.  Particle Mass  Charge  Location  P roton   1 amu  +1  In the nucleus   Neutron  1 amu   0