Physical and chemical properties of the elements are the periodic function of their atomic numbers. The long form of the periodic table, also called Modem Periodic Table, is based on Modern periodic law. In this table, the elements have been arranged in order of increasing atomic numbers. This chapter is considered by many to be of vital importance since it covers concepts that are an essential part of the syllabus for classes 11 & 12 (CBSE), JEE, and NEET. The topics covered in this chapter include: