For class ten: compare and contrast between Mendeleev's periodic table and Moseley's periodic table.

Mendeleev’s periodic table is, based on the relation of elements’ properties as dependent on the atomic weight of the element. But the Modern periodic table considers atomic number as the fundamental property that decides the properties of elements.

The modern periodic table does correct the defects of Mendeleev’s periodic table. For example, in Mendeleev’s periodic table, in the element pairs, Argon-potassium, cobalt-nickel, tellurium-iodine and thorium and protactinium, elements with higher atomic mass precede the element with lower atomic weight. However, it is the right places for them but is against Mendeleev’s periodic law.

These elements atomic number shows the reverse order compared to atomic mass. The supposed to be wrong positions in Mendeleev’s table has the right explanation justifying their positions.