The modern periodic law states that “The physical and chemical properties of elements are periodic functions of their atomic numbers” This was the most accurate description we have today and it is in agreement with the quantum mechanical model of the atom. The periodic table can be classified into the
- ‘s’ block,
- ‘p’ block,
- ‘d’ block and
- ‘f’ block elements.
The electrons when filled in according to the Aufbau order we find the modern periodic table can represent them appropriately.
This periodic table can also be classified into
- Representative elements: The ‘s’ and the ‘p’ block elements excluding group 18
- Transition elements: The ‘d’ block elements
- Inner transition elements ‘f’ block elements
- Noble gases: Group 18 elements
Mendeleev’s periodic table (1869) : Mendeleev is credited for actually organizing the elements in the periodic table, he arranged elements in the increasing order of atomic weights, he stated that the “Physical and Chemical properties of elements were periodic functions of their atomic weights” This is called the periodic law according to Menedeleev.
The advantages of this periodic table was that he could predict the properties of elements like germanium even when they were not discovered.
Newland’s law of octaves: John alexander Reina Newland in 1864 observed that every eight element showed similar physical and chemical characteristics, so he tried to arrange the elements of increasing order of atomic weights. But this pattern was not repeated as the atomic weights increased and today we know why.
Doebereiner’s Triads: John Dobereiner was a german chemist who grouped the elements with similar properties in sets of three