Mendeleev’s Periodic table

Q: why did mendeleev used sanskrit language while naming of elements?

Mendeleev used Sanskrit prefixes eka‑ (one), dvi‑ (two), and tri‑ (three) to temporarily name predicted elements based on their positions relative to known ones—for instance, eka‑silicon was the element directly below silicon. He also admired the two-dimensional structure of the Sanskrit alphabet (varṇamālā)—which grouped sounds by pronunciation features—and saw a parallel in his periodic arrangement of elements, honoring ancient grammarian Pāṇini with this naming approach.

Edited By Shivani Poonia | Updated on Jul 02, 2025 05:53 PM IST

Dmitri Mendeleev's formulation of the Periodic Table in 1869 stands as a pivotal advancement in the field of chemistry, profoundly altering our comprehension of elemental relationships. By systematically arranging elements in order of increasing atomic mass, Mendeleev discerned recurring patterns in their chemical properties, leading to the establishment of the periodic law. This innovative approach not only facilitated the classification of known elements but also enabled the prediction of properties for undiscovered ones. His work continues to be a cornerstone in the study of chemistry, underscoring the significance of periodicity in elemental properties.

This Story also Contains

Mendeleev's Periodic Table: Pioneer to the arrangement of elements.
Correction of doubtful atomic weights:
Defects of Mendeleev's Periodic Table:
Lother Meyer:
Solved Examples Based On Mendeleev's Periodic Table
Conclusion

Mendeleev’s Periodic table

This topic is integral to the Class 11 Chemistry curriculum under the Classification of Elements and Periodicity in propeties chapter. Understanding Mendeleev's contributions is crucial not only for academic examinations but also for competitive assessments such as JEE Main, NEET, and other entrance tests. Notably, the concept was featured in the JEE exam in 2021, highlighting its enduring relevance in the field of chemistry.

Mendeleev's Periodic Table: Pioneer to the arrangement of elements.

Dmitri Mendeleev:

Dmitri Mendeleev's formulation of the Periodic Law and his development of the Periodic Table marked a transformative moment in chemistry. At a time when the structure of atoms was not yet understood, Mendeleev's insight that the properties of elements are related to their atomic masses was groundbreaking. While constructing the table, he arranged elements by increasing atomic mass and grouped them based on similar chemical properties. Recognizing that some elements did not fit this arrangement, Mendeleev took the bold step of reversing the order of certain elements to maintain consistency in the table's structure.

Moreover, Mendeleev demonstrated remarkable foresight by leaving gaps in his table for elements that were not yet discovered. He predicted the properties of these missing elements based on the trends he observed among known elements. His predictions proved astonishingly accurate upon the discovery of these elements. For instance, he predicted the existence of gallium, which was discovered in 1875, and germanium, discovered in 1886, both of which exhibited properties closely matching Mendeleev's forecasts .

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Mendeleev's Periodic Law not only organized the known elements but also provided a predictive framework that spurred further research and discovery in the field of chemistry. His work laid the foundation for the modern periodic table and continues to influence scientific thought and education today.

Mendeleev's Periodic Table:

Mendeleev's periodic law: The physical and chemical properties of elements are the periodic function of their atomic weight
Characteristic of Mendeleev's periodic table :
- It is based on atomic weight
- 63 elements were known, but noble gases were not discovered.
- He was the first scientist to classify the elements in a systematic manner i.e. in horizontal rows and vertical columns.
- Horizontal rows are called periods and there were 7 periods in Mendeleev's Periodic table.
- Vertical columns are called groups and there were 8 groups in Mendeleev's Periodic table.
- Each group up to VIIth is divided into A & B subgroups.'A' sub-group elements are called normal elements and 'B' sub-group elements are called transition elements.
- The VIIIth group consisted of 9 elements in three rows (Transitional metals group).
- The elements belonging to the same group exhibit similar properties.
Merits or Advantages of Mendeleev's periodic table :

Study of elements: First time all known elements were classified according to their similar properties. So study of the properties of elements becomes easier.
Prediction of new elements: It encouraged the discovery of new elements as some gaps were left in it.
Sc (Scandium) Ga (Gallium) Ge (Germanium) Tc (Technetium)

These were the elements for whom position and properties were well defined by Mendeleev even before their discoveries and he left the blank spaces for them in his table.

Ex. Blank space at atomic weight 72 in the silicon group was called Eka silicon (which means properties like silicon) and the element discovered later was named Germanium.

Similarly, other elements discovered after Mendeleev's periodic table were.

Eka aluminium – Gallium(Ga)

Eka Boron – Scandium (Sc)

Eka Silicon – Germanium (Ge)

Eka Manganese – Technetium (Tc)

Correction of doubtful atomic weights:

Correction was done in the atomic weight of some elements.

Atomic weight = Valency × Equivalent weight.

Initially, it was found that the equivalent weight of Be is 4.5 and it is trivalent (V = 3), so the weight of Be was 13.5 and there is no space in Mendeleev's table for this element. So, after correction, it was found that Be is divalent (V = 2). So, the weight of Be became 2 × 4.5 = 9 and there was a space between Li and B for this element in Mendeleev's table.

– Corrections were done in the atomic weight of elements are – U, Be, In, Au,

Defects of Mendeleev's Periodic Table:

The position of hydrogen is uncertain. It has been placed in the lA and VII-A groups because of its resemblance with both groups.
No separate positions were given to isotopes.
It is not clear whether the lanthanides and actinides are related to IIA or IIB group.
Although there is no resemblance except the valency of subgroups A and B, they have been put in the same group.
The order of increasing atomic weights is not strictly followed in the arrangement of elements in the periodic table. E.g. – Co (At. wt. 58.9) is placed before I (127) and Ar (39.9) before K (39).

Lother Meyer:

He plotted a curve between the atomic weight and the atomic volume of different elements.
The following observations can be made from the curve –
1. Most electropositive elements i.e. alkali metals (Li, Na, K, Rb, Cs, etc.) occupy the peak positions on the curve.
2. Less electropositive i.e. alkali earth metals (Be, Mg, Ca, Sr, Ba) occupy the descending position on the curve.
3. Metalloids (B, Si, As, Te, At, etc.) and transition metals occupy the bottom part of the curve.
4. Most electronegative i.e. halogens (F, Cl, Br, I) occupy the ascending position on the curve.

Note: Elements having similar properties occupy similar positions on the curve.

Based on this curve Lother Meyer proposed that the physical properties of the elements are periodic functions of their atomic wt. and this becomes the base of Mendeleev's periodic table.

Solved Examples Based On Mendeleev's Periodic Table

Example 1: Eka-aluminium and Eka-silicon are respectively known as:

1) Aluminium and silicon

2) Silicon and aluminium

3) Gallium and germanium

4) Gallium and Tin

Solution:

According to Mendeleev’s periodic table, Eka-aluminium is known as gallium and Eka-silicon is known as germanium.

Hence, the answer is the option (3).

Example 2: Mendeleev’s periodic table is based on:

1) Atomic number

2) Atomic weight

3) Ionization enthalpy

4) None of the above

Solution

Mendeleev arranged the elements in horizontal rows and vertical columns in his table in order of their increasing atomic weights. In this way, elements with similar properties occupied the same vertical column.

Hence, the answer is the option (2).

Example 3: Which of the following statements is not correct about Lother Meyer’s curve?

1) The alkali metals occupy the maxima of the curve

2) The transition metals occupy the minimum of the curve.

3) The halogens occupy positions on the descending portions of the curve.

4) The alkali earth metals occupy mid positions on the descending portions of the curve.

Solution: The Lother Meyer curve. Thus, halogens occupy positions on the ascending portions of the curve.

Therefore, Option(3) is correct.

Practice more Questions from the link given below:

Mendeleev’s Periodic table -Practice questions and MCQs

Long form of Modern periodic table -Practice questions and MCQs

Conclusion

Thanks to the great genius of one of the most outstanding chemists in history, mankind has acquired a unique publication, the Periodic Table of Mendeleev. His way of organizing the elements might be great because not only offered a system of knowing the properties of the elements but also opened doors for further interpretations and breakthroughs in chemistry. In the way that he guessed at and calculated the probable location and characteristics of still undiscovered elements, Mendeleev proved anew the fruitfulness of the mental exercise of rational processes complemented by the observation of the facts. Nevertheless, the further elaboration and modifications, which have been made to the Periodic Table by other chemists, people remember the genius of Mendeleev’s work, which played a crucial role in the formation of contemporary chemistry.

Frequently Asked Questions (FAQs)

1. What is Mendeleev’s Periodic Table?

Mendeleev's Periodic Table is an arrangement of chemical elements organized by increasing atomic mass. Proposed by Dmitri Mendeleev in 1869, it grouped elements with similar chemical properties into columns, revealing periodic trends in their behaviors.

2. How did Mendeleev arrange the elements?

Mendeleev arranged elements in rows (periods) and columns (groups) based on their atomic masses. He placed elements with similar properties in the same vertical columns, leaving gaps for elements that were yet to be discovered.

3. What is the Periodic Law according to Mendeleev?

Mendeleev's Periodic Law states that "the physical and chemical properties of elements are periodic functions of their atomic masses." This means that elements show recurring trends in properties when arranged by increasing atomic mass.

4. Did Mendeleev leave gaps in his table?

Yes, Mendeleev left gaps in his periodic table for elements that had not yet been discovered. He predicted the properties of these missing elements, and many were later discovered, confirming his predictions.

5. How did Mendeleev handle elements with similar properties but different atomic masses?

In cases where elements with similar properties had different atomic masses, Mendeleev sometimes placed them out of order to maintain the consistency of chemical properties within groups. For example, he placed iodine before tellurium, despite iodine having a higher atomic mass, because iodine's properties were more similar to those of other halogens.

6. What is the difference between Modern and Mendeleev's periodic table?

Mendeleev’s table (1869) arranged 63 known elements by increasing atomic mass, grouped similar properties, and left gaps predicting elements like gallium and germanium .

Modern periodic table orders all 118 elements by atomic number, includes noble gases and transition blocks, and naturally resolves earlier anomalies without gaps .

7. What are limitations of Mendeleev's periodic Table?

Mendeleev’s periodic table struggled to place hydrogen logically, forced some heavier elements before lighter ones to maintain group traits (like Co/Ni or Te/I), and couldn’t address isotopes, noble gases, or f‑block elements due to its reliance on atomic mass.

8. why did mendeleev used sanskrit language while naming of elements?

Mendeleev used Sanskrit prefixes eka‑ (one), dvi‑ (two), and tri‑ (three) to temporarily name predicted elements based on their positions relative to known ones—for instance, eka‑silicon was the element directly below silicon. He also admired the two-dimensional structure of the Sanskrit alphabet (varṇamālā)—which grouped sounds by pronunciation features—and saw a parallel in his periodic arrangement of elements, honoring ancient grammarian Pāṇini with this naming approach.

9. How did Mendeleev's table differ from the modern periodic table we use today?

Mendeleev's table was based on atomic weights, while the modern table is organized by atomic number. The modern table also includes elements discovered after Mendeleev's time and incorporates our understanding of electron configurations.

10. Why did Mendeleev sometimes place elements out of order in his table?

Mendeleev occasionally placed elements out of atomic weight order to maintain chemical property patterns. For example, he swapped tellurium and iodine to keep iodine with other halogens, prioritizing chemical behavior over strict atomic weight ordering.

11. How did Mendeleev's table contribute to the discovery of noble gases?

While Mendeleev didn't initially include noble gases, their later discovery fit perfectly into a new group in his table. This demonstrated the table's flexibility and predictive power, even for element types unknown during its creation.

12. What are "groups" and "periods" in Mendeleev's periodic table?

Groups are vertical columns in the table, containing elements with similar chemical properties. Periods are horizontal rows, representing elements with increasing atomic weights and changing properties across the row.

13. What was the impact of Mendeleev's periodic table on the field of chemistry?

Mendeleev's table revolutionized chemistry by providing a systematic framework for understanding element relationships, predicting new elements, and guiding further research. It became a fundamental tool in chemistry education and research.

14. Why is Mendeleev's periodic table considered a breakthrough in chemistry?

Mendeleev's periodic table was revolutionary because it organized elements based on their atomic weights and chemical properties, allowing for the prediction of undiscovered elements. It provided a systematic way to understand element relationships and trends in properties, laying the foundation for modern chemistry.

15. How did Mendeleev arrange elements in his periodic table?

Mendeleev arranged elements in order of increasing atomic weight, grouping those with similar properties in vertical columns. He left gaps for undiscovered elements and even predicted their properties, demonstrating the table's predictive power.

16. What was unique about Mendeleev's approach compared to earlier classification attempts?

Mendeleev's approach was unique because he focused on both atomic weights and chemical properties, whereas earlier attempts relied solely on atomic weights. This allowed him to identify patterns and make accurate predictions about unknown elements.

17. How did Mendeleev's periodic table account for elements that were yet to be discovered?

Mendeleev left gaps in his table for undiscovered elements, predicting their properties based on the trends he observed. This foresight allowed for the later discovery and confirmation of elements like gallium, scandium, and germanium.

18. What is the significance of the term "periodic" in Mendeleev's periodic table?

The term "periodic" refers to the recurring patterns of properties observed as atomic weights increase. Mendeleev noticed that elements with similar properties appeared at regular intervals, forming a periodic pattern across the table.

19. How did Mendeleev's table help in correcting atomic weights of some elements?

When elements didn't fit the patterns Mendeleev observed, he suggested their reported atomic weights might be incorrect. In several cases, such as with beryllium, later experiments proved Mendeleev right, leading to corrections in atomic weight measurements.

20. How did Mendeleev's table contribute to the understanding of element abundance in nature?

While not a primary focus, Mendeleev's table indirectly reflected patterns in element abundance. Elements in even-numbered groups, for instance, tend to be more abundant, a pattern that became clearer with further geological studies.

21. What role did the concept of valence play in Mendeleev's periodic table?

Valence, or the combining power of elements, was a crucial factor in Mendeleev's organization. He grouped elements with similar valences together, which helped identify chemical similarities and trends across the table.

22. How did Mendeleev's table handle isotopes?

Mendeleev's table predated the discovery of isotopes. It used average atomic weights, which we now know can vary due to isotopic composition. This occasionally led to ordering issues that were later resolved in the modern periodic table.

23. What were some limitations of Mendeleev's periodic table?

Limitations included its basis on atomic weights rather than atomic numbers, inability to explain why elements exhibited periodicity, and difficulties in placing some elements like lanthanides and actinides.

24. How did Mendeleev's table account for the lanthanides and actinides?

Mendeleev's original table didn't fully account for lanthanides and actinides, as many were undiscovered at the time. Later versions attempted to incorporate them, but their placement remained a challenge until the development of the modern periodic table.

25. What is the connection between Mendeleev's table and electron configuration?

While Mendeleev's table predated the discovery of electron configuration, its organization inadvertently reflected electron structure. The groups in his table correspond to elements with similar outer electron configurations, explaining their chemical similarities.

26. How did Mendeleev's table predict the properties of undiscovered elements?

Mendeleev predicted properties of unknown elements by examining the trends in properties of known elements in the same group and neighboring elements. He estimated properties like atomic weight, density, and reactivity based on these patterns.

27. What role did the concept of atomic number play in the evolution of Mendeleev's table?

Atomic number wasn't known during Mendeleev's time, but its later discovery by Moseley led to a refinement of the periodic table. It explained some inconsistencies in Mendeleev's arrangement and became the basis for the modern periodic table.

28. How did Mendeleev's table handle elements with very similar properties, like transition metals?

Mendeleev grouped similar elements together, including transition metals. However, the subtle differences among transition metals were not fully explained by his table, which was a limitation addressed in later versions of the periodic table.

29. What was the significance of Mendeleev's prediction of "eka-elements"?

Mendeleev's prediction of "eka-elements" (elements yet to be discovered) demonstrated the predictive power of his table. He accurately described properties of elements like eka-silicon (later discovered as germanium), which greatly enhanced the credibility of his work.

30. How did Mendeleev's table contribute to our understanding of element families?

Mendeleev's arrangement grouped elements with similar properties into families (like halogens and alkali metals), providing a clear visualization of chemical relationships and trends across the periodic table.

31. What was the role of oxidation states in Mendeleev's classification?

While not explicitly using the term "oxidation states," Mendeleev considered the combining ratios of elements, which are related to oxidation states. This helped him group elements with similar chemical behaviors.

32. How did Mendeleev's table handle the placement of hydrogen?

The placement of hydrogen was challenging in Mendeleev's table, as it shares properties with both alkali metals and halogens. This ambiguity in hydrogen's placement persists even in modern periodic tables.

33. What impact did Mendeleev's work have on the discovery of new elements?

Mendeleev's work provided a roadmap for element discovery. Chemists actively searched for elements fitting the gaps in his table, leading to the discovery of several new elements that matched his predictions.

34. How did Mendeleev's table explain the similarity between certain pairs of elements (like lithium and magnesium)?

Mendeleev's table revealed diagonal relationships between certain elements, such as lithium and magnesium. These relationships, while not fully explained at the time, hinted at underlying patterns in electron configuration and atomic size.

35. What was the significance of Mendeleev's decision to leave gaps in his table?

Leaving gaps showed Mendeleev's confidence in his system and its predictive power. It demonstrated that the periodic law was robust enough to accommodate undiscovered elements, making it a powerful tool for future research.

36. How did Mendeleev's table handle elements with very high atomic weights?

Mendeleev's original table had limitations in dealing with very heavy elements, many of which were unknown at the time. The placement of these elements became clearer with the discovery of atomic number and the development of the modern periodic table.

37. What was the relationship between Mendeleev's periodic table and the law of octaves?

Newlands' law of octaves was an earlier attempt at element classification that Mendeleev improved upon. While the law of octaves noted some periodicity, Mendeleev's table provided a more comprehensive and accurate representation of elemental relationships.

38. How did Mendeleev's table account for the different physical states of elements?

Mendeleev's table indirectly reflected the physical states of elements. Elements in the same group often have similar physical states, a pattern that emerged from his arrangement based on chemical properties and atomic weights.

39. What role did valence electrons play in Mendeleev's classification, even though they weren't yet discovered?

Although valence electrons weren't known, Mendeleev's grouping of elements with similar chemical properties inadvertently grouped elements with similar valence electron configurations, foreshadowing later discoveries in atomic structure.

40. How did Mendeleev's table contribute to the understanding of element reactivity trends?

Mendeleev's arrangement revealed trends in reactivity across periods and down groups. These trends, while not fully explained at the time, later correlated with factors like atomic size and electron configuration.

41. What was the significance of Mendeleev's prediction of element properties in terms of compounds they would form?

Mendeleev not only predicted properties of elements but also the nature of compounds they would form. This demonstrated the table's power in predicting chemical behavior, not just physical properties.

42. How did Mendeleev's table handle elements with very similar atomic weights?

When faced with elements of similar atomic weights, Mendeleev prioritized chemical properties over strict atomic weight ordering. This sometimes led to pairs of elements being swapped to maintain chemical trend consistency.

43. What was the impact of Mendeleev's work on the understanding of chemical bonding?

While Mendeleev's work predated modern theories of chemical bonding, his grouping of elements with similar properties laid the groundwork for understanding valence and, later, electron sharing in chemical bonds.

44. How did Mendeleev's table reflect the relationship between an element's position and its properties?

Mendeleev's table showed that an element's properties are periodic functions of its position in the table. This fundamental insight remains a cornerstone of modern chemistry, explaining trends in properties across the periodic table.

45. What was the significance of Mendeleev's work in standardizing element names and symbols?

Mendeleev's work contributed to the standardization of element names and symbols, promoting consistency in chemical communication. This was particularly important for newly discovered or predicted elements.

46. How did Mendeleev's table handle elements with multiple oxidation states?

While not explicitly addressing multiple oxidation states, Mendeleev's grouping often placed elements with variable oxidation states together, indirectly reflecting this property. This became clearer with later understanding of electron configuration.

47. What role did atomic volume play in Mendeleev's classification system?

Mendeleev considered atomic volume as one of the properties that showed periodicity. He noted that atomic volume generally increases down a group and varies across a period, contributing to the overall periodic trends.

48. How did Mendeleev's work influence the development of quantum mechanics?

While Mendeleev's work predated quantum mechanics, the periodic patterns he observed later found explanation in quantum theory. His table provided empirical evidence that supported the development of quantum mechanical models of the atom.

49. What was the significance of Mendeleev's table in predicting the properties of compounds?

Mendeleev's table allowed for predictions about the properties of compounds based on the position of constituent elements. This predictive power extended beyond elemental properties to molecular and material characteristics.

50. What was the role of Mendeleev's table in the development of spectroscopy?

Mendeleev's work coincided with advances in spectroscopy. His predictions of element properties helped guide spectroscopic searches for new elements, demonstrating the synergy between theoretical and experimental chemistry.

51. How did Mendeleev's table handle the concept of isotopes, which were unknown at the time?

Mendeleev's table used average atomic weights, unknowingly incorporating the effects of isotopes. The later discovery of isotopes explained some of the inconsistencies in his atomic weight-based ordering.

52. What was the significance of Mendeleev's work in the context of the atomic theory of matter?

Mendeleev's work provided strong support for the atomic theory of matter, demonstrating that elements had distinct, quantifiable properties that followed predictable patterns, reinforcing the concept of discrete atomic units.

53. How did Mendeleev's table reflect the relationship between an element's properties and its atomic structure?

Although atomic structure was not yet understood, Mendeleev's table inadvertently reflected relationships between properties and what we now know as electron configuration. This laid the groundwork for later explanations of periodic trends.

54. What was the impact of Mendeleev's work on the understanding of chemical reactions?

Mendeleev's classification helped in understanding and predicting chemical reactions. Elements in the same group often undergo similar reactions, a pattern that became a powerful tool in chemical synthesis and analysis.

55. How did Mendeleev's table contribute to the development of inorganic nomenclature?

Mendeleev's systematic arrangement of elements influenced the development of systematic naming conventions in inorganic chemistry, particularly for compounds involving elements from different groups.

56. What was the significance of Mendeleev's work in the context of the history of scientific classification systems?

Mendeleev's periodic table stands as one of the most important classification systems in science history. It demonstrated how systematic organization of empirical data could lead to powerful predictive models, influencing approaches in other scientific fields.

57. How did Mendeleev's table handle the concept of atomic radius, which wasn't yet fully understood?

While atomic radius wasn't explicitly part of Mendeleev's work, his arrangement indirectly reflected trends in atomic size. Elements in the same group often have similar atomic radii, a pattern that became clearer with later atomic models.

58. What was the role of Mendeleev's periodic table in bridging classical and modern chemistry?

Mendeleev's periodic table served as a bridge between classical chemistry, based largely on observable properties, and modern chemistry, rooted in atomic structure. It provided a framework that could accommodate new discoveries and theories, facilitating the transition to our current understanding of chemical elements and their behavior.