ATOMIC STUCTURE

Atomic StructureThe minimum negative potential which can stop the fastest moving photoelectron is called cut off potential, that is is called cut off potential. Maximum kinetic energy (KEmax) of photoelectrons is directly proportional to the frequency (u) of incident light and is independent of its intensity. Order of wave lengths-Cosmic rays < X -rays < X rays < UV rays < visible < IR < microwaves < radiowaves  Moseley’s equation - where v = frequency, z = atomic number, a and b are constant. For any spectral line  and  For multi-electron systems, energy depends on both principal quantum number (n) and azimuthal quantum number Using Bohr’s theory one is able to calculate the energy (E), radii(r), speed (v) and wave number (n) by using the certain formulae. These formulae are applicable only for one-electron system such as H, He+, Li3+ and so on and not for multi electron system. S-orbitals only possess radial nodes  These nodes are also known as spherical nodes. The angular momentum of an electron in an orbit is calculated by using the formula . characterises only the orbital while gives the probability of finding the electron in an orbital. IITJEE- Basic conceptual questions are generally asked simple but time consuming questions are also important which are require fast calculation. Some topics like Bohr’s atomic model, photoelectric effect and heisenberg’s uncertainty principle are most important as per the trends of recent year exam.