Mendleeve’s Periodic Table
Mendeleev in the same year 1869 unknown of the Lother Meyer’s arrangement gave the most successful and detailed periodic table. He stated that “The properties of elements whether physical or chemical are periodic functions of their atomic masses”. Based on his law he arranged all the attempts known at that time in a table called the Periodic Table, which later on became the basis of the arrangement of elements for the Modern Periodic Table. He called the vertical column ‘Groups’ and horizontal rows ‘Periods’.
Features of Mendeleeve’s Periodic Table
Important features of Mendeleeve’s Periodic Table are listed below:
- It was the most simplified arrangement of elements based on their properties. One can easily guess the property of elements placed in a particular group.
- He corrected the atomic masses of elements such as Beryllium, Gold, Indium, etc.
- He left vacant positions for some elements that were not known at that time but he predicted such elements would exist in the future. He added the prefix ‘eka’ to those elements. For Example, Eka Aluminium was Gallium, Eka-Silicon was Germanium.
Drawbacks of Mendeleeve’s Periodic Table
Following are the drawbacks of Mendeleeve’s Defect
- The position of Hydrogen was not defined. Hydrogen resembles properties with that of alkali metals as well as halogens but was placed in the group of alkali metals. He couldn’t explain why hydrogen will not be in the halogen group although both are nonmetals.
- There exists anomalous pair in the table which would not follow the law of increasing atomic weight. For Example, Argon (39.9 u) was placed before K (39.1) and Co was placed before Ni.
- Since the table was based on increasing order of atomic mass but the position of isotopes was not defined as isotopes have different masses.
- The position of Lanthanoids and Actinoids was not assigned separately.
- Similar atoms were placed in different groups while dissimilar atoms were placed in the same groups. For example, Alkali Metals Li, Na, and K were placed together with Cu, Ag, and Au, even though their properties are quite dissimilar.
Periodic Classification of Elements
Periodic Classification of Elements refers to the arrangement of elements on the basis of the periodic repetition of their properties. It means the elements which exhibit similar properties on a regular interval are placed in the same group.
In this article, we will learn about, History of the Classification of Elements, various ways to classify elements, their drawbacks, and others in detail in this article.