Question

Which element was not present in mendeleev periodic table?

Answer 1

Alumimim, Boron were not present in Mendeleev Periodic Table.

Answer 2

Hydrogen is the element which is not present in Mendeleev periodic table.

Hydrogen exclusion in Mendeleev periodic table:

Hydrogen could not be fixedly placed in Mendeleev periodic table because it showed alternative characters like, resembling an alkali metal (since it can form positive ions) and resembling halogen (since it can form diatomic molecule).

Mendeleev periodic table:

• Dmitri Ivanovich Mendeléev was a Russian chemist who formulated the most accepted form of periodic table in 1869. The elements in Mendeleev's periodic table are arranged in the basis of their atomic mass, fundamental and chemical properties.
• His representation of the elements in his table follows vertical columns, in which elements with similar properties are grouped together. His observance let to the finding that, "the properties of elements are the periodic function of their atomic masses."
• The demerits of his table includes, inability to locate the position of hydrogen in the period table, irregular increase in atomic masses hence newer elements are difficult to predict and discovery of isotopes violated his law.