Posts

Showing posts from July, 2020

CHEMICAL BONDING AND MOLECULAR STRUCTURE

-
Image
                    1. Introduction Matter is made up of one or different type of elements. Under normal conditions no other element exists as an  independent atom in nature, except noble gases. However, a group of atoms is found to exist together as one species having characteristic properties. Such a group of atoms is called a molecule. Obviously there must be some force which holds these constituent atoms together in the molecules. The attractive force which holds various  constituents (atoms, ions, etc.) together in different chemical species is called a chemical bond. Since the formation of chemical compounds takes place as a result of combination of atoms of various elements in different ways, it raises many questions. Why do atoms combine? Why are only certain combinations possible? Why do some  atoms combine while certain others do not? Why do molecules possess definite shapes? To answer such questions differen...
Post a Comment
Read more

Classification of elements and periodicity of elements

-
Image
               1. Introduction The Periodic Table as it stands today and the Modern Periodic Law. We will also learn how the periodic classification follows as a logical consequence of the electronic configuration of atoms. Finally, we shall examine some of the periodic trends in the physical and chemical properties of the elements.    WHY DO WE NEED TO CLASSIFY ELEMENTS ? We know by now that the elements are the basic units of all types of matter. In 1800, only 31 elements were known. By 1865, the number of identified elements had more than doubled to 63. At present 118 elements are known. Of them, the recently discovered elements are man-made. Efforts to synthesise new elements are continuing. With such a large number of elements it is very difficult to study  individually the chemistry of all these elements and their innumerable compounds individually. To ease out this problem, scientists searched for a systematic way to...
Post a Comment
Read more

STRUCTURE OF ATOM

-
Image
                1. Introduction The existence of atoms has been proposed since the time of early Indian and Greek philosophers (400 B.C.) who were of the view that atoms are the fundamental building  blocks of matter. According to them, the continued subdivisions of matter would ultimately yield atoms which would not be further divisible. The word ‘atom’ has been  derived from the Greek word ‘a-tom io’ which means ‘uncut-able’ or ‘non-divisible’. These earlier ideas were mere speculations and there was no way to test them experimentally. These ideas remained dormant for a very long time and were revived again by scientists in the  nineteenth century. The atomic theory of matter was first proposed on a firm scientific basis by John Dalton, a British school  teacher in 1808. His theory, called Dalton’s atomic theory, regarded the atom as the ultimate particle of matter. Dalton’s atomic theory was able to explain the law of co...
2 comments
Read more

Youtube videos

-
Image
                       1. Introduction
Post a Comment
Read more

SOME BASIC CONCEPTS OF CHEMISTRY

-
Image
       1. DEVELOPMENT OF CHEMISTRY Chemistry, as we understand it today, is not a very old   discipline. Chemistry was not studied for its own sake, rather   it came up as a result of search for two interesting things: i. Philosopher’s stone (Paras) which would convert  all baser metals e.g., iron and copper into gold. i i.‘E lex i r of life’ which would grant immortality. People in ancient India, already had the knowledge of many   scientific phenomenon much before the advent of modern science. They applied that knowledge in various walks of   life. Chemistry developed mainly in the form of Alchemy   and Iatrochemistry during 1300-1600 CE. Modern   chemistry took shape in the 18th century Europe, after a  f ew centuries of alchemical traditions which were introduced in Europe by the Arabs. Other cultures – especially the Chinese and   the Indian – had their own alchemical traditions. These included much knowledge of ch...
Post a Comment
Read more

WAVES

-
Image
                             1. INTRODUCTION In this topic we will study about the waves. A material medium provides   such an example. Here, elastic forces bind the constituents   to each other and, therefore, the motion of one affects that of   the other. If you drop a little pebble in a pond of still water,   the water surface gets disturbed. The disturbance does not   remain confined to one place, but propagates outward along a circle. If you continue dropping pebbles in the pond, you   see circles rapidly moving outward from the point where the   water surface is disturbed. It gives a feeling as if the water is   moving outward from the point of disturbance. If you put   some cork pieces on the disturbed surface, it is seen that the cork pieces move up and down but do not move away   from the centre of  disturbance. This shows...
Post a Comment
Read more

OSCILLATIONS

-
Image
                            1. INTRODUCTION You have already learnt about some of them, e.g., rectilinear   motion and motion of a projectile. Both these motions are   non-repetitive. We have also learnt about uniform circular   motion and orbital motion of planets in the solar system. In   these cases, the motion is repeated after a certain interval of   time, that is, it is periodic. In your childhood, you must have   enjoyed rocking in a cradle or swinging on a swing. Both   these motions are repetitive in nature but different from the   periodic motion of a planet. Here, the object moves to and fro   about a mean position. The pendulum of a wall clock executes   a similar motion. Examples of such periodic to and fro   motion abound: a boat tossing up and down in a river, the   piston in a steam engine going back and forth, etc. Such a   mo...
Post a Comment
Read more

KINETIC THEORY

-
                    1. INTRODUCTION In this topic we will know about kinetics theory. Boyle discovered the law named after him in 1661. Boyle,   Newton and several others tried to explain the behaviour of   gases by considering that gases are made up of tiny atomic   particles. The actual atomic theory got established more than   150 years later. Kinetic theory explains the behaviour of gases   based on the idea that the gas consists of rapidly moving   atoms or molecules. This is possible as the inter-atomic forces, which are short range forces that are important for solids   and liquids, can be neglected for gases.   The kinetic theory   was developed in the nineteenth century by Maxwell,   Boltzmann and others. It has been remarkably successful. It   gives a molecular interpretation of pressure and temperature of a gas, and is consistent with gas laws and Avogadro...
Post a Comment
Read more

Popular posts from this blog

QUANTUM NUMBERS (Principal, Azimuthal, Magnetic and Spin)

-
Image
                  QUANTUM NUMBERS  Orbitals represent regions in the space around the nucleus where the probability of finding the electron is maximum. A large number of electron orbitals are possible in atom. These can be distinguished by their size, shape and orientation of the orbitals. To describe each electron in an atom in different orbitals, we need a set of three numbers known as quantum numbers. These are designated as n, l and m. In addition to these three numbers another quantum number is also needed which specifies the spin of the electron. These four numbers are called quantum numbers. These are discussed below: 1. Principal quantum number (n) :  This quantum number determines the main energy shell or level in which the electron is present. It is denoted by n. It can have whole number values starting from 1 such as n = 1, 2, 3, 4 ... This quantum number also identifies as shell. The shell with n 1 is called the first sh...
Read more

Diagonal Relationship between Beryllium and Aluminium || Relation between Beryllium and Aluminium

-
  Diagonal Relationship between Beryllium and Aluminium The ionic radius of Beryllium (Be 2+) is estimated to be nearly 31 pm; the charge/radius ratio Or e/m ratio is nearly the same as that of the Al 3+ ion. Hence beryllium resembles aluminium in these ways. Some of the similarities are given below: » Like Aluminium, Beryllium(be) is not readily attacked by acids H+ donor because of the formation of an oxide film on the surface of the metal by reacting with oxygen, i.e. they are rendered passive by nitric acid. » Beryllium hydroxide[[Be(OH)4]2] dissolves in excess of alkali to give a beryllate ion, [ Be(OH)4]2– just as aluminium hydroxide[Al(OH)3] gives aluminate ion, [Al(OH)4] » The chlorides of metals beryllium and aluminium have Cl– bridged chloride structure in vapour phase. Both the chlorides are soluble in organic solvents and are strong as Lewis acids They are used as Friedel Craft catalysts. » Beryllium(Be) and aluminium(Al) ions have strong tendency to form complexes, (Be...
Read more

Math question

-
Image
A tower, x metre, has a flagstaff at its top. The tower and flagstaff subtends equal angles at a point distant y metre from the foot of the tower. Then find the length of the flagstaff ( in metre). 
Read more

Solar System, Planets, Moons, Asteroid Belt,Kuiper Belt and Oort Cloud, Comets and Meteoroids

-
Image
 The solar system consists of the Sun, which is a star at its center, and all the celestial bodies bound by its gravitational pull. These bodies include planets, moons, asteroids, comets, and other objects. Key Components of the Solar System: The Sun : The Sun is the center of the solar system and contains about 99.86% of its mass. It is a star primarily composed of hydrogen and helium, providing the heat and light that sustains life on Earth. Planets : There are eight recognized planets in the solar system: Mercury : The closest planet to the Sun, known for extreme temperature variations and no atmosphere. Venus : Similar in size to Earth but with a thick, toxic atmosphere and surface temperatures hot enough to melt lead. Earth : The third planet from the Sun, the only known planet to support life, with water and a breathable atmosphere. Mars : Known as the Red Planet, it has a cold, dry surface and signs of past water. Jupiter : The largest planet, a gas giant, w...
Read more