The concept of an atom is DEMOCRITUS & JOHN DALTON

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1 ATOMIC STRUCTURE

2 HISTORY OF THE ATOM The concept of an atom is originated i from Greek philosophers h DEMOCRITUS & JOHN DALTON

3 HISTORY OF THE ATOM Democritus Democritus studied the nature of matter and the constituents of all the substances

4 HISTORY OF THE ATOM In 1808, John Dalton put forward atomic theory to explain the laws of chemical combination. According to him, an atom is the smallest unit of matter which takes part in a chemical reaction. He considered that atoms are indivisible particles. Vikasana- Bridge course 2012 John Dalton

5 Modern Concept of An Atom was developed by J.J Thomson, Goldstein, Rutherford, Bohr and other Scientists. Modern Concept of An Atom was developed by JJTh J.J Thomson, Goldstein, Rutherford, Bohr and other Scientists. Vikasana Bridge course 2012

6 Modern concept of an Atom Atom consists of smaller particles (sub atomic particles) called Fundamental particles. Electron Proton Neutron.

7 Modern concept of an Atom The atom contains nucleus at its center,, which has positively charged protons & neutral neutrons. Electrons are revolving around the nucleus &they carry ve charge.

8 ELECTRON(e ) J J Thomson discovered electron in Mass of an Electron = 9.107x10-28 g = 9.107x kg Charge of an Electron = Unit ve charge = 1.602x10-19 coulombs The charge of e - was measured by R A Millikan in 1939.

9 PROTON E Goldstein discovered proton in Mass of proton = 1.672x10-24 g = 1.672x10-27 kg Charge of proton = Unit +ve charge = x10-19 coulomb

10 NEUTRON James Chadwick discovered neutron in 1932 Mass of neutron =1.675x10-24 g =1.675x10-27 kg Charge of neutron = carry no charge i.e. NEUTRAL

11 ORBIT Orbit is a well defined circular path around the nucleus in which an electron revolves.

12 Continued Orbit of definite it energy levels l called shells.these shells are named as K,L,M and N and numbered as 123 1,2,3, and d4 respectively from the nucleus. An orbit (shell) can accommodate electrons equal to 2n 2.

13 Continued For K Shell, n =1 maximum no of e - s in K shell =2n 2 =2(1) 2 =2 Therefore maximum no of electrons in K shell = 2

14 Continued Similarly, For L shell, n=2, maximum no. of electrons = 08 For M shell,n =3, maximum no. of electrons = 18 For N shell,n = 4, maximum no. of electrons = 32

15 ORBITAL Orbital is the three dimensional region around the nucleus where the probability of finding electron density is maximum. All orbital have definite shape and each can accommodate maximum of two electrons in it. Obi Orbitals are named as s, p, d and df.

16 s orbital Continued. Shapes of Orbitals p orbitals

17 Continued. d Orbitals f Orbitalas

18 Continued. s orbital can accommodate 2 electrons. There are three p orbital, each can accommodate two electrons therefore totally p orbital can accommodate 6 electrons. There are five d orbital so they can accommodate maximum of 10 electrons and there are seven f orbital and they can accommodate14 electrons.

19 ENERGY LEVEL The relative energies of various orbital can be shown by an arrangement and is called as ENERGY LEVEL diagram.

20 Schematic diagram to remember sequence of filling electrons in atomic orbitals

21 ELECTRONIC CONFIGURATION Distribution of electrons in various orbital in the increasing energy level is called as electronic configuration.

22 Electronic Configuration Elements Symbol Atomic No of Electronic No. Electrons configuration Hydrogen H 1 1 1s 1 Helium He 2 2 1s 2 Lithium Li 3 3 1s 2 2s 1 Beryllium Be 4 4 1s 2 2s 2 Boron B 5 5 1s 2 2s 2 2p 1 Carbon C 6 6 1s 2 2s 2 2p 2 Neon Ne s 2 2s 2 2p 6

23 Elements Electronic Configuration Symb ol Atomic NO. No of Electrons Electronic configuration Sodium Na s 2 2s 2 2p 6 3s 1 Magnesium Mg s 2 2s 2 2p 6 3s 2 Aluminium Al s 2 2s 2 2p 6 3s 2 3p 1 Argon Ar s 2 2s 2 2p 6 3s 2 3p 6 Potassium K s 2 2s 2 2p 6 3s 2 3p 6 4s 1

24 Elements Electronic Configuration Symb ol Atomic NO. No of Electrons Electronic configuration Calcium Ca s 2 2s 2 2p 6 3s 2 3p 6 4s 2 Scandium Sc s 2 2s 2 2p 6 3s 2 3p 6 4s 2 3d 1