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

Bases Substances with bitter taste and give a soapy touch are known as bases but many bases have corrosive nature. So bases are defined as "  According to Arrhenius : those substances which give hydroxide or hydroxyl ion (OH - ) in their aqueous solution" are called bases. Properties of Bases The following are the characteristic properties of bases:  1. Taste and Touch  Bases have a bitter taste and their solutions are soapy to touch. 2. Action on indicators . The colours shown by three commonly used indicators in presence of bases are listed below for easy recall.    colours of some common indicators in basic solution  Indicator  colour in basic medium    1. Litmus  Blue    2. Phenolphthalein  Pink    3. Methyl orange  Yellow   3.Conduction of electricity and dissociation of bases  Aqueous solutions (solution in water ) of basesconduct electricity which is due to the forma

properties and classification of acids  We can categorize a substance as an acid or a base according to the properties. Let us learn the characteristics properties of acids. Properties of acids The following are the characteristic properties of acids: 1.Taste :  The sour taste of many unripe fruits , lemon , vinegar and sour milk is caused by the acids present in them. Hence , we can say that acids have a sour taste.                                                                            Acids present in some substances . 2. Action on indicators .  Indicators show different colours in presence of acid and bases . The three commonly used indicator in presence of acids.                                  colour of some indicator in presence of acids .  3. Conduction of electricity and dissociation of acids  When acids are dissolve in water they produce ions which help in conducting the electricity. This process is known as dissociation . More specifically , acids

 INDICATORS   The substances which are neither acidic nor basic and are chemically inert in nature. Touching or tasting of acid or base is very harmful and hence typical indicators are used to recognise them. The substances which change their colours in presence of acid or base are called ‘Indicators’.  you might have seen that the spot of turmeric on cloth becomes red when soap is applied on it. what do you think has happened? Tumeric has acted as an indicator of base present in soap. There are many substances that shows one colour in an acidic medium and another colour in a basic medium. such substances are called acid base indicator.  litums is a natural dye founded in certain lichens. It was the earliest indicator to be used. it shows red colour in acidic medium and blue colour in basic solutions . phenolphthalein and methyl orange are some other indicators. The colour of these indicator in acidic, neutral and basic solutions are given below in the table. Indicato

ACIDS AND BASES     For thousands of years, people have known that vinegar, lemon juice, amla, tamarind and many other food items taste sour. However, only a few hundred years ago it was proposed that these things taste sour because they  contain 'acids'. The term acid comes from Latin term 'accre' which means sour . It was first used in the seventeenth century by robert boyle to label substance as acids and bases according to the following characteristics.   While Robert Boyle was sussessful in characterising acids and bases he could not explain their behaviour on the basis of their chemical structure.This was accomplished by Swedish scientist  Svante Arrhenius in the late nineteenth century. He proposed thaton dissolving in water , manycompounds dissociate and form ions and their properties are mainly the properties of the ions they form. Governed by this, he identified the ions furnished by acids and bases responsible for thier characteristics behaviour a