FILL IN THE BLANKS 1. Periodic classification is based on the _________ and __________ properties of the substance. 2. __________ gave the law of octave. 3. The horizontals rows of the table are called _________. 4. The sub-groups containing the typical or normal elements are called _________ sub-group. 5. The 6th period contain _____________ elements. 6. Due to scarcity the inner transitions elements are also called. 7. The elements of group IA are also called ___________.