Electronic Configuration Of Elements

The distribution of electrons into different shells, sub shells and orbitals of an atom is called its electronic configuration. The electronic configuration of any orbital can be represented as:  nlx n is the number of principal shell, l = symbol of the sub shell or orbital, x= number of electrons present in the orbital 4p1 means that…

Energy Level Diagram

Energies of orbitals of hydrogen and hydrogen like particles depend upon the value of principal quantum (n) number only , those of multi-electron atoms depend both upon principal quantum number( n ) as well as azimuthal quantum number(l). Diagram representing the arrangement of orbitals in order of their increasing energies are called energy level diagrams….

Shapes of atomic orbital

An orbital is the region of space around the nucleus within which the probability of finding an electron of given energy is maximum. The probability at any point around the nucleus is calculated using schrodinger wave equation and is represented by the density of the points. Shape of s orbital For the coordinates( x, y,…

Pauli Exclusion Principle

Wolfgang Pauli a German physicist in 1925 put forward a principle known after his name as Pauli exclusion principle. No two electrons in an atom can have the same set of four quantum number. In an atom ,any two electrons may have the same values for any of the three quantum numbers but the 4th…

Quantum numbers

An atom contains a large number of orbitals. These are distinguished from each other on the basis of their shape ,size and orientation in space. These characteristics of an orbital are expressed in terms of three numbers, called principal, azimuthal and magnetic quantum number. Quantum numbers may be defined as a set of 4 numbers…

Quantum mechanical model of an atom

​Quantum mechanics, as developed by Erwin Schrodinger in 1926, is based on the wave motion associated with the particles. For the wave motion of the electron in the three dimensional space around the nucleus, he put forward an equation known as Schrondinger wave equation. where ψ is the amplitude of the wave where the coordinates…

Heisenberg’s Uncertainty Principle

​Werner Heisenberg, a German physicist, in 1927 gave a principle about the uncertainty in simultaneous measurement of position and momentum of small particles. Heisenberg’s uncertainty Principle states that: It is impossible to measure simultaneously the position and momentum of a small particle with absolute accuracy or certainty.The product of the uncertainty in the position (…

Dual Nature of Matter and Radiation

​Einstein in 1905 suggested that light has dual nature, ie wave nature as well as particle nature. Louis de Broglie, a French physicist, in 1924, suggested that all microscopic as well as macroscopic objects possesses dual character. The wave associated with the particle is called a matter wave or a de Broglie wave. The wavelength…

Hydrogen spectrum

​Hydrogen Spectrum Atomic spectrum of hydrogen consists of a number of lines which have been grouped into 5 series :Lyman, Balmer, Paschen, Brackett and Pfund. Any given sample of hydrogen gas gas contains a large number of molecules. When such a sample is heated to a high temperature or an electric discharge is passed, the…

Bohr’s Model of an atom

​Neils Bohr, a Danish physicist in 1913 proposed a new model of atom. This new model is called Bohr’s Model of atom. Postulates of Bohr’s model of an atom 1)An atom consists of a small, heavy positively charged nucleus in the centre and electrons revolve around it in circular orbit. 2)The electrons revolve only in…

Absorption and Emission Spectra

Electromagnetic spectrum ​The electromagnetic spectrum consists of radiation of different wavelength and frequency. An instrument used to separate the radiations of different wavelength is called spectroscope or spectrograph. A spectroscope consists of a prism or a diffraction grating for the dispersion of radiation and a photographic film to examine the emergent radiation with the human…

Electromagnetic Wave Theory

Electromagnetic wave theory ​This theory was put forward by James clark Maxwell in 1864. The main points of this theory are: 1)The energy is emitted from any source continuously in the form of radiations and is called the radiant energy. 2)The radiations consist of electric and magnetic fields oscillating perpendicular to each other and both…

Rutherford’s Model Of An Atom

​Thomson’s model of atom J.J. Thomson in 1904, proposed that an atom was a sphere of positive electricity in which were embedded number of electrons. The stability of the atom was explained as a result of the balance between the repulsive forces between the electrons and their attraction towards the centre of the positive Sphere.This…

Discovery Of Proton

​Since the atom as a whole is electrically neutral and the presence of negatively charged particles in it was established ,therefore, it was thought that some positively charged particles must also be present in the atom. Goldstein in 1886 performed discharge tube experiment in which he took perforated cathode and a gas at low pressure was…

Discovery Of Electron

​William crookes in 1879 studied the conduction of electricity through gases at low pressure. EXPERIMENTAL SET UP 1)He took a discharge tube which is a long glass tube, sealed at both the ends and fitted with two metal electrodes. 2)It has a side tube fitted with a stop cock which can be connected to a…