5 Achievements and limitations of Mendeleev's Periodic table
Mendeleev's Periodic Table: Mendeleev was a Russian scientist. Mendeleev arranged the periodic table in different-different ways. But he succeed when he arrange all the then known 63 elements in the order of increasing atomic mass.
The benefits of doing so is, those elements having the similar properties comes under the vertical line of those elements which arranged in horizontal line. But Mendeleev sure that the elements having the same properties fell in same vertical column or group. So that's why Mendeleev left some gap in his periodic table.
There are two main features of Mendeleev Periodic table.
- Increasing atomic mass
- Grouping in horizontal and vertical line of all the elements having similar properties.
But there are limitations and achievements of Mendeleev's Periodic table. following are the three main Achievements of Mendeleev's Periodic table.
5 Achievement of Mendeleev's Periodic table
Mendeleev Periodic table helps to understand the properties of the elements. Means many of the elements having same properties has only explains with the help of Mendeleev Periodic table.
- First achievement of Mendeleev is he predicted the existence of some elements that was not discovered at that time.
- Mendeleev left some gap of undiscovered elements in his periodic table. And when those elements were discovered later, it was placed on those gaps without disturbing the existing elements.
- Mendeleev predicted the prefix name (in Sanskrit) of undiscovered elements as same when it was discovered later. (which is Gallium, germanium, and scandium).
- Mendeleev's periodic table predicts the properties of several elements on the basis of their position but at that time Gallium, scandium and germanium were not discovered. even it was found to be almost same as the actual properties when these elements were discovered.
- When noble gas were discovered, it got a place in Mendeleev's periodic table without disturbing the existing elements.
5 Limitations of Mendeleev's Periodic table
- Mendeleev's could not able to explain the positions of the Isotopes in periodic table.
- Mendeleev arranged the elements in the order of increasing atomic mass. But in some cases it was found that the elements having higher atomic mass comes first than the lower atomic mass element.
- Some of the elements have two atomic mass and if we arranged it in Mendeleev's periodic law hen two elements comes in one box which was not explained.
- Mendeleev didn't assigned the correct position of the hydrogen element in his periodic table.
- Hydrogen element could be placed in both alkali group as well as halogen group but Mendeleev's periodic law didn't assign the correct position of hydrogen element.
5 Achievements and limitations of Mendeleev's Periodic table Elaborate in more detail.
Achievements of Mendeleev’s Periodic Table:
- Systematic Arrangement: Mendeleev arranged elements in increasing order of atomic mass and grouped them based on similar properties, creating the first organized periodic table.
- Prediction of New Elements: He left gaps for undiscovered elements (e.g., gallium, scandium, and germanium) and accurately predicted their properties.
- Correction of Atomic Masses: He corrected the atomic masses of some elements (e.g., beryllium, indium) based on their properties and placement in the table.
- Grouping of Elements: Elements with similar chemical properties were placed in the same group, which helped in understanding trends in reactivity.
- Periodic Law: He formulated the Periodic Law, stating that "the properties of elements are a periodic function of their atomic masses," laying the foundation for modern periodic classification.
Limitations of Mendeleev’s Periodic Table:
- Position of Hydrogen: Hydrogen was placed in Group 1 with alkali metals, but it also showed similarities with halogens, making its position uncertain.
- Anomalous Pairing of Elements: Some elements (e.g., argon & potassium, cobalt & nickel) did not follow the increasing atomic mass rule but were placed according to properties.
- No Fixed Position for Isotopes: Isotopes (atoms of the same element with different atomic masses) were not accommodated in the table.
- Irregular Placement of Some Elements: Certain elements, like lanthanides and actinides, had no proper place in the table.
- Based on Atomic Mass Instead of Atomic Number: The table was based on atomic mass rather than atomic number, which later led to inconsistencies that were corrected by Moseley’s Modern Periodic Table.
