Inside An Atom

Hello Friends,
I have made this PPT especially for 10th Standard students of Maharashtra State Board (SSC). This PPT is made highly informative and illustrative, so that each and everyone of you can understand the basics of Science.
Best of Luck!

1. COME ON, LETS SEE WHAT IS INSIDE AN ATOM? -BY FURQAAN

2. ILLUSTRATIONS OF THE COMPOSITION OF THE HUMAN BODY

3. HISTORICAL BACKGROUND OF atom’S STRUCTURE In approximately 430B.C., Democritus coined the term atomos , which means “ uncuttable ” or “the smallest indivisible particle of matter”. In 1803 A.D John Dalton put forth his celebrated atomic theory.According to him, Matter is made of small particles called atoms. Atoms cannot be created, divided into smaller particles, nor destroyed in the chemical processes.

4. THOMSON’S THEORY OF ATOM John Thomson in 1867 developed the idea that atoms are made of negative electrons embedded in a gel of positive charge (A P lum P udding).

5. RUTHERFORD’S SCATTERING EXPERIMENT Rutherford overtuned Thomson’s atom model in 1911 with his well-known gold foil experiment in which he demonstrated that the atom has a tiny, massive nucleus. Rutherford designed an experiment to use alpha particles emitted by a radioactive element as probes to the unseen world ofatomic structure.

6. Using these observations he formulated the theory of an atom.According to this theory: An atom has a tiny, dense, positively charged core called a nucleus, in which nearly all the mass is concentrated. The light, negative constituents, called electrons, revolve around the nucleus in paths called orbits.This is much like a solar system where planets revolve around the sun.

7. Rutherford’s model had certain limitations.It could not eplain how the moving electron would remain in its orbit, especially when it is was a charged particle and therefore it would accelerate due to its movement, finally moving closer to the nucleus and drop into it.The atom would not be stable which in turn would mean that matter would not be composed of unstable atoms.

8. NIELS BOHR’S ATOMIC MODEL Nobel Prize winner, Niels Bohr in 1922, revised Rutherford’s model by suggesting that: The electrons were confined into clearly defined orbits. They could jump between these orbits, but could not freely spiral inward or outward in intermediate states. An electron must absorb or emit specific amounts of energy for transition between these f ixed orbits.

9. DISCOVERY OF NEUTRON James Chadwick in 1932 discovered another particle inside the atom.It had no charge and its mass was almost equal to the mass of the proton.It was present in the nucleus along with the proton.He named it as the ‘Neutron’.

10. DISTRIBUTION OF ELECTRONS IN ORBITS Let us now see how these electrons are organised.According to Bohr, electrons move in the stationary orbits (also called shells) which are associated with a certain amount of energy.

11. The orbit closest to the nucleus is given the number ‘1’, the second orbit the number ‘2’ and so on.They are also named as K, L, M, N,…….. Corresponding to the shell numbers, like n=1, 2, 3, 4,……The number of maximum electrons in each orbit is given by a formula 2n 2 .The following table gives the maximum number of electrons in each orbit.

12. ELECTRONIC CONFIGURATION OF ELEMENTS The arrangement of electrons of each element in their orbits or shells is known as its electronic configuration. You have seen that K, L, M, N,…… Shells occupy 2, 8, 18, 32,… electrons respectively.

13. Every electron has a fixed amount of energy depending on which orbit it is present in. Electrons in the first orbit i.e. K have minimum energy. Electrons in the subsequent orbit posses higher energy. Electrons in an atom occupy shells in increasing order of energies.

14. THE ELECTRONIC CONFIGURATION OF ATOMS OF SOME ELEMENTS

15. ATOMIC NUMBER Atomic number (Z) is the number of protons present in an atom. An atom of an element is electrically neutral.The number of protons and electrons are equal.

16. ATOMIC MASS NUMBER Atomic masses are measured in a unit called Dalton (u).A Dalton is approximately equal to 1 atomic mass unit ( amu ) which is equal to 1.6 x 10 -27 Kg. The mass of a proton, neutron and electron is approximately 1 u, 1 u and 0.0055 u respectively.So you can realize how less the mass of electron is a s compared to the masses of proton and neutron.

17. Hence, while calculating mass of an atom of an element, we only add up the mass of proton and neutron.The atomic Mass of an element is equal to the sum of the number of protons and neutrons present in the nucleus of the element.It is called the mass number and denoted by symbol A. The atomic number and mass number of an element can be represented symbolically as: For e.g: 11 Na. Z A Symbol of the element 23

18. ISOTOPES AND THEIR APPLICATION In nature it is found that many elements have atoms with the same atomic number but different atomic mass number. Such atoms of the same elements are called isotopes.Many elements have isotopes and a mixture of them is present in the element. e.g : Carbon exists in two isotopic form 12 C and 14 C. The number of neutrons in isotopes is different.The chemical properties of isotopes are the same though some physical properties may different.

19. USES OF ISOTOPES Isotopes are widely used for different purposes:- Uranium -235 ( 235 U) is used for nuclear fission. Isotopes of some elements are used in the medical treatment of deadly diseases like cancer. Iodine ( 131 I) is used in the treatment of goitre , a disease of the thyroid glands. Goitre

20. ISOBARS There are a number of different elements whose atomic mass numbers are same.Such atoms are called Isobars. For Example:

21. THANKS FOR YOUR ATTENTION