Explain the comparison of Mendeleev and Modern periodic table?
Comparison of Mendeleev and Modern periodic table
S.No. | Characteristic | Mendeleev Periodic Table | Modern Periodic Table |
1. | Arrangement of elements | In Mendeleev's periodic table elements are arranged in increasing order of their atomic weight. | In the modern periodic table, elements are arranged according to their increasing atomic number. |
2. | Position of isotopes (elements with the same atomic number but with different mass numbers) | In Mendeleev's periodic table isotopes of every element were given a different place | In the modern periodic table, isotopes were placed with the element itself. |
3. | Number of elements | Mendeleev’s periodic table was for the arrangement of 63 elements known at that time. | The modern table accommodates all the 118 natural and synthetic elements. |
4. | Uneven grouping of elements | In Mendeleev’s periodic table, coinage metals like copper, silver, and gold are grouped with very active alkali metals. Manganese metal was grouped with halogens in the seventh group. | This defect was rectified in the Modern periodic table. |
5 | Anomaly in Mendeleev's table | In Mendeleev’s periodic table the element pairs, Argon-potassium, cobalt-nickel, tellurium-iodine, and thorium and protactinium, elements with higher atomic mass precede the element with lower atomic mass. It is the right place for them but is against Mendeleev’s periodic law. | The modern periodic table rectifies the defects of Mendeleev’s periodic table. |
6 | Number of periods and groups | Mendeleev's periodic table was divided into 7 periods and 8 groups and each group is further subdivided into subgroups. | The modern periodic table is divided into 18 groups and 7 periods. |