Describe briefly Mendeleeff's periodic table along with its merits.

Dmitri Mendeleev, a Russian chemist, developed the periodic table in 1869. He arranged the known elements in a table according to their increasing atomic weights and observed a periodic pattern in their properties. The table had horizontal rows called periods, and vertical columns called groups. Elements in the same group had similar chemical properties. Mendeleev left some gaps in his table, predicting the existence of yet-undiscovered elements that would fit into those spaces.

1. Prediction of new elements: One of the significant merits of Mendeleev's periodic table was its ability to predict the existence of undiscovered elements. He left gaps in his table where he believed new elements would fit based on the observed periodic pattern. This prediction was later validated with the discovery of new elements like gallium, scandium, and germanium. 2. Correcting atomic weights: Mendeleev's table helped to correct the atomic weights of some elements based on their position in the table. For example, the atomic weight of indium and tellurium were revised based on their placement in the table. 3. Grouping of elements with similar properties: The arrangement of elements in groups based on their similar properties allowed chemists to easily study and understand the elements' chemical behavior. This gave a systematic way for organizing and remembering the properties of the known elements. 4. Basis for modern periodic table: Mendeleev's periodic table laid the foundation for the development of the modern periodic table. The later discovery of atomic numbers and the periodic law allowed scientists to refine and perfect Mendeleev's table, making it more accurate and easier to use. Today, the periodic table is an essential tool in chemistry, helping students and chemists understand the properties and relationships of the elements.