Answer :

Explanation:

Mendeleev's Periodic Table is a classification system for the chemical elements based on their atomic numbers, electron configurations, and recurring chemical properties. In this table, elements are arranged in order of increasing atomic number, and elements with similar properties are placed in the same group or column.

Eka-Aluminium is the name given by Mendeleev to the hypothetical element that he predicted would fill the gap in his periodic table below aluminium. He made certain predictions about the properties of this element based on its position in the table.

Among the given options, the element that replaced eka-Aluminium in Mendeleev's Periodic Table is Gallium (option B).

Gallium was discovered by the French chemist Paul-Émile Lecoq de Boisbaudran in 1875. Its discovery confirmed Mendeleev's predictions about the properties of the missing element eka-Aluminium.

Here is a brief explanation of why Gallium replaced eka-Aluminium:

1. Atomic number and properties: Gallium has an atomic number of 31, which is the same as the predicted atomic number of eka-Aluminium. Mendeleev predicted that eka-Aluminium would have an atomic weight of around 68 and similar properties to aluminium. Gallium fits these predictions as it has an atomic weight of 69.72 and exhibits similar properties to aluminium, such as being a soft, silvery metal.

2. Group placement: Gallium is placed in Group 13 of the periodic table, along with aluminium and boron. Mendeleev predicted that eka-Aluminium would be located in this group. The elements in Group 13 have similar chemical properties, including the ability to form trivalent cations.

3. Physical properties: Gallium shares several physical properties with aluminium. Both elements have relatively low melting points and densities. For example, aluminium has a melting point of 660.3 °C, while gallium has a melting point of 29.76 °C, making it one of the few metals that are liquid near room temperature.

In conclusion, Gallium replaced eka-Aluminium in Mendeleev's Periodic Table because it fulfilled the predictions made by Mendeleev regarding the atomic number, properties, and group placement of eka-Aluminium.

Gallium replaced eka -Aluminium mendeleev's