Question

Use Mendeleev’s periodic law to predict the formula of oxides of potassium, aluminium and barium.

Answer 1

Mendeleev’ s periodic table was the first periodic table to carry out the classification of elements . The elements were arranged according to the relative atomic masses. We will use the Mendeleev’s periodic law to determine the formula of oxides of potassium, aluminium and barium.

Complete step by step answer:
Mendeleev’s periodic table was a table developed by Mendeleev for the classification of elements. We know that oxygen is a member of the group (VI) A in Mendeleev’s periodic table. Its valency is two. Similarly all the valencies of all elements can be predicted from their respective groups. This helps us in writing the formula of their oxides. Now, let us discuss each element given in question one by one:
1. Potassium ($K$) is the member of group (IA) of Mendeleev’s periodic table. Its valency is one. The general formula of oxide of element in this group is${R_2}O$. Therefore oxide of potassium will possess formula as${K_2}O$.
2. Aluminium ($Al$) belongs to group (III A) and its valency is three. The general formula of oxide of element in this group is${R_2}{O_3}$. So the formula of oxide of aluminium is$A{l_2}{O_3}$.
3. Barium ($Ba$) belongs to group (IIA) so the valency of barium is two. The general formula of oxide of element in this group is$RO$. So the formula of oxide of barium is$BaO$.
Therefore the formula of the oxides of potassium, aluminium and barium are${K_2}O,A{l_2}{O_3},BaO$ respectively.

Note: There were some improvements needed in the Mendeleev’s periodic table. Moseley improved it and it arranged them in the increasing order of atomic numbers. Position of hydrogen was fixed at number one.