Differentiate between the arrangement of elements in Mendeleev's periodic table and the modern periodic table.

Mendeleev’s Periodic Table

Modern Periodic Table

• Mendeleev's periodic table is based on atomic mass. Elements are arranged in increasing order of their atomic masses.

• Modern periodic table is based on atomic number. Elements are arranged in increasing order of their atomic numbers.

• There are no separate positions for isotopes of an element as their atomic masses are different.

• Separate positions are not required as they have same atomic numbers.

• Some elements of higher atomic masses have been placed before elements of lower atomic masses.

• No such problems occur in this table. All elements are in proper order.

• Some dissimilar elements are grouped together while some similar elements are not grouped together.

• All similar elements are grouped together.

• Electronic configuration of an element cannot be calculated from its position.

• Electronic configuration of an element can be easily calculated from its position.

• Mendeleev's periodic table contains about 66 elements.

• Modern periodic table contains about 112 elements.