Elements-Classification of Elements-Groupwise Study of Elements

One of the most important concepts of science is the classification of elements based on their properties and their Groupwise Study of Elements. The first table of elements was written by chemist Dmitri Mendeleev in 1869. The periodic table of elements arranged the elements based on their atomic numbers and their physical and chemical properties. The table is always divided into rows, called periods, and columns, called groups.

Classification Of Elements

Classification of elements is the grouping of elements with comparable qualities. While each constituent is unique, certain elements have commonalities. Based on these commonalities, chemists were able to arrange elements into groups or chemical families, with comparable elements clustered together and different elements separated. The periodic table is formed by classifying elements.

Dobereiner’s Triads – Origin of the Periodic Classification

Dobereiner ordered several elements with comparable properties in various groups consisting of three elements in 1829, with the middle element’s atomic mass almost equal to the average atomic mass of the first and third elements. 

Dobereiner’s Triads’ Limitations

Dobereiner’s triads were useful for grouping together elements with comparable qualities, Newly discovered elements did not fit into the triads. Only a total of 5 Dobereiner’s triads were identified.

Newlands’ Law of Octaves

When elements are grouped in order of increasing atomic mass, John Newlands proposed the law of octaves, which states that every eighth element has properties comparable to the first. Because a similar link exists in musical notes as well, Newlands named it the law of octaves.

Drawbacks of Newlands’ Law of Octaves

• Only the element calcium was successfully classified. After then, no eighth member in the same group had the same attributes as the element above it.
• When noble gas components were identified later, they disrupted the overall arrangement.

Mendeleev’s Periodic Table

The physical and chemical properties of elements are periodic functions of the atomic masses of these elements, according to Mendeleev’s Periodic Law. The periodic table was created by Mendeleev, who organised the elements which were known at that time in order of growing atomic masses. Vertical rows of elements which have similar attributes were referred to as groups. Periods referred to the horizontal rows.

Key points about Mendeleev’s table:

• The elements are grouped in Mendeleev’s table in vertical rows called groups as well as horizontal rows called periods.
• The Roman numerals from I to VIII, and 0 represent the nine groupings. Group VIII is made with nine elements organised into three triads. The zero group contains elements that are either inert or noble gases, and all of the elements in the group have zero valency.
• In Mendeleev’s periodic table, there are seven periods (numbered between 1-7) or horizontal rows.

Importance of Mendeleev’s Periodic Table

• This made the Groupwise Study of Element more systematic. In other words, the table made it possible to predict the properties of elements with the help of the characteristics of a single element present in a particular group.
• This helped in discovering these elements at a later time.
• With the help of their anticipated placements and properties, Mendeleev adjusted the atomic mass of several elements.

Limitations in Mendeleev’s Table

• Hydrogen, along with alkali metals, is classified as part of Group IA. However, it shares several properties with group VII A halogens. As a result, its place in Mendeleev’s periodic table remains debatable.
• Although the elements present in Mendeleev’s periodic table are listed in order of atomic mass, the element which has a greater atomic mass sometimes comes before the element which has a lesser atomic mass.
• Isotopes of a given element have varying atomic masses and the exact atomic number, as we know. Because Mendeleev’s periodic table was created based on elements’ rising atomic masses, all of the isotopes of a given element are bound to be assigned to different positions.
• According to Mendeleev, elements that are placed together in a  group should be having properties that are similar. However, we see no similarity between the elements that are placed inside two different sub-groups of the same group.
• Elements with comparable properties have been grouped together in some circumstances.
• Lanthanoids and actinoids were placed in two separate rows at the bottom of the periodic table.
• There is no satisfactory explanation for placing elements with similar properties in a specific group.

Need For Classification Of Elements

Conclusion

The classification of elements was very necessary to understand periodic trend in physical and chemical properties of elements . The periodic table of elements arranged the elements based on their atomic numbers and their physical and chemical properties.

The study of properties of elements became easier after an arrangement of elements in the periodic table.