The Mendeleev Periodic Table was a way of organizing chemical elements so they were easier to study and understand. It was created by Dmitri Mendeleev, who noticed that elements with similar properties appeared at regular intervals when arranged by atomic mass. His table made it perfect, the Mendeleev Periodic Table was a major step forward in science and helped shape the modern periodic table we use today.

Mendeleev’s Periodic Table

Dmitri Mendeleev created one of the earliest versions of the periodic table by arranging elements in order of increasing atomic weight. He placed elements with similar properties in the same vertical columns called groups, which helped show patterns in their behavior.

Chemistry Notes Free PDFs

His table had:

• 7 horizontal rows called periods 
• 8 vertical columns called groups

Mendeleev believed that "The properties of elements are a periodic function of their atomic weights.” In simple terms, this means that the properties of elements repeat at regular intervals when arranged by their atomic weight. His work laid the foundation for today’s modern periodic table, and was a major step forward in understanding the elements and their relationships.

• Mendeleev arranged the elements in 7 rows (called periods) and 8 columns (called groups).
• These groups were marked with Roman numerals and divided into A and B subgroups based on similar properties.
  Group 8 included 9 elements, grouped into sets of three (called triads) with similar behaviors.
• He also left empty spaces in the table for elements that hadn’t been discovered yet and later, many of those elements were found and fit perfectly into those spots.
• When noble gases were discovered, they were placed in a new column called the zero group, and this was done without disrupting the rest of the table.

Merits of Mendles Periodic Table

• Mendeleev’s periodic table had several strengths that made it a major step forward in understanding the elements.
• Firstly, it brought a proper system to the classification of elements. Instead of being randomly listed, the elements were grouped based on similar properties, making the table organised and easy to study.
• One of the most impressive things Mendeleev did was leave blank spaces in the table. He believed that some elements hadn’t been discovered yet– and he was right! Later, when those elements were found, they fit perfectly into the gaps he had predicted, with properties very close to what he had expected.
• Another major achievement was that Mendeleev managed to correct the atomic masses of several elements. By carefully analyzing where they should go in the table, he realised that some of the earlier values were wrong and suggested corrections- many which turned out to be accurate.

Demerits of Mendles Periodic Table

• One major issue was with the placement of hydrogen. Mendeleev couldn’t clearly decide where it should be placed because hydrogen shares properties with both alkali metals and halogens. The table also didn’t account for isotopes– atoms of the same element that have the same atomic number but different atomic masses– since Mendeleev’s arrangement was based on atomic mass.
• Another problem was with the lanthanides and actinides. These elements didn't quite fit into the pattern of Mendeleev’s periodic law, and their positions in the table remained unclear.
• Additionally, although elements in the same group were supposed to have similar properties, this wasn’t always the case. Some elements with similar properties were placed far apart, while others with different properties ended up in the same group– which led to some confusion.

Difference Between Mendeleev and Modern Periodic Table

Hope this article was informative and helpful for your studies and exam preparations. Stay tuned on the Testbook app for more updates and topics related to Chemistry and various such subjects. Also, reach out to the test series available to examine your knowledge regarding related exams.