CHEMISTRY

media type="youtube" key="JNPFR-22MPA" height="344" width="425"
 * Electronic Configuration**

Mendeleev noticed the recurrence of properties of elements as the atomic weight increased, and he invented the [|Periodic Table of Element], which is a useful tool for organizing and correlating chemical and physical properties of chemical elements. Today, the most popular Periodic Table form is shaped by results of quantum theory. Quantum theory rationalized the existence of and arrangement of all elements in today's Periodic Table. It has also been applied to explain their chemical properties.

When two electrons occupy the same orbital, they not only have different spins (Pauli exclusion principle ), the pairing raises the energy slightly. On the other hand, a half filled sub shell and a full filled sub shell lower the energy, gaining some stability. Bearing this in mind, you will be able to understand why we have the following special electronic configurations.