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Shapes of orbitals, Shape of s orbital, The probability of finding electron belonging to s-orbital is found to be identical, in all directions at a given distance from nucleus. Hence s orbital is spherical in, shape which is symmetrical around the nucleus., , s orbital, , Shape of p-orbital, It is found that probability of finding the p-electrons is maximum in two lobes on, the opposite sides of nucleus. This give rise to dumb-bell shape for p-orbital., , p orbital, Filling of orbitals in atoms, The filling of electrons into the orbitals of different atoms takes place according, to the following three rules., 1. Aufbau principle, The aufbau principle (building-up principle), also called the aufbau, rule, states that in the ground state of an atom or ion, electrons fill, atomic orbitals of the lowest available energy levels before occupying, higher levels., Or

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In the ground state of an atom the orbitals are filled in order of their, increasing energy., , 2. Pauli exclusion principle, “No two electrons in an atom can have the same set of four quantum, numbers.”, , Pauli exclusion principle can also be stated as, “Only two electrons may exist in the same orbital and these electrons, must have opposite spin.”, 3. Hund’s rule of maximum multiplicity, Pairing of electrons in the orbitals belonging to the same sub-shell (p,, d, or f) does not takes place until each orbital belonging to that subshell has got one electron each.