Question

What physical and chemical properties of elements were used by Mendeleev
in creating his periodic table? List two observations which posed a challenge to
Mendeleev’s Periodic Law

Answer 1

Explanation:

Various anomalies of Mendeleev’s Periodic Table removed as follows in the Modern Periodic Table:

→ Elements are arranged in the increasing order of their atomic number in Modern Periodic Table, thus there was no need for keeping more than one element in one slot.

→ In Modern Periodic Table there was no problem of the place of isotopes, as isotopes have same atomic mass with different atomic numbers.

→ Elements having same valence electron are kept in same group.

→ Elements having same number of shells were put under the same period.

→ Position of hydrogen became clarified in as it is kept in the group with the elements of same valence electrons.