Question

Fill in the blanks with regards to the defect of the Mendeleev periodic table.

-------- as not assigned a definite position.

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 called periods.
• During the arrangement, there were seven periods and eight groups in Mendeleev's periodic table.

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

Position of Hydrogen:

• It resembles alkali metals by losing one electron and forming positive ions.
• It resembles halogens by forming a diatomic molecule and combines with metals and non-metals to form covalent compounds.
• It was considered in Group IA as well as in Group VIIA.

Thus, Hydrogen was not assigned a definite position.