Question

Mendeleev's periodic table also suffered from a lot of defects. Answer the following questions in keeping in mind the defects of Mendeleev's periodic table.

Why the position of isotopes was considered a defect?

Answer 1

Mendeleev periodic table

In Mendeleev, periodic table elements were arranged based on increasing atomic mass. During Mendeleev, only 63 elements were known so after studying the properties of elements he arranged them into vertical columns called groups and horizontal rows are called periods.

Although Mendeleev resolved many of the previous limitations in previous arrangements but is suffered from some limitations such as:

Position of Isotopes:

• The atoms of the same element having similar chemical properties but different atomic masses are called isotopes.
• Since isotopes have different atomic masses, they should be placed in different places in the periodic table if they are arranged according to atomic masses.
• In Mendeleev’s periodic table, the isotopes were not given their column so the isotopes are arranged in the same place.
• For example, Cl-35 and Cl-37 are two isotopes of chlorine with atomic weights of 35 and 37, respectively and they are assigned the same place.