Mendeleev introduced his periodic table in 1869. He arranged the elements based on their atomic mass.
Mendeleev’s Periodic Table
He introduced a famous law that element properties are periodic functions of their atomic weight.
The modern periodic table is the arrangement of elements based on modern periodic law.
Modern Periodic Table:
It states that the properties of elements are periodic functions of their atomic number.
In Mendeleev’s periodic table, elements are organised based on their atomic mass.
Composition of Mendeleev’s periodic table and the modern periodic table
But elements are organised based on their atomic number in the modern periodic table.
Mendeleev’s periodic table includes 63 elements, but the modern periodic table includes 118 elements.
Mendeleev’s periodic table comprises 8 groups and 7 periods, but the modern periodic table comprises 18 groups and 7 periods.
Mendeleev’s periodic table has some spaces to place undiscovered elements, but the modern periodic table maintains uniformity.
In Mendeleev’s periodic table, noble gases were not placed because they were not yet discovered. But in the modern periodic table, noble gases are placed in separate groups.
In Mendeleev’s periodic table, isotopes are not placed, but isotopes are placed separately in the modern periodic table.