1. Which are the elements predicted by Mendeleev in his periodic table before the actual discovery of the elements?
Mendeleev left spaces for eka- aluminium which later was found out to be gallium and eka-silicon was Germanium. He also predicted the properties of these elements.
2. Define Mendeleev’s periodic law?
“The Physical and Chemical Properties of the Elements are Periodic Functions of Their Atomic Masses,” according to Mendeleev's periodic law.
3. In the modern periodic table, what is the total number of elements?
The modern periodic table contains 118 elements.
4. What is Mendeleev's crowning achievement?
Mendeleev is most known for developing the periodic law and the periodic table of elements, which he developed in 1869.
5. What is the difference between Mendeleev's periodic table and the modern periodic table?
The main difference is that element in Mendeleev's periodic table are arranged by atomic mass as well as modern periodic table arrange element by atomic number. As element are constantly being discovered there were significantly fewer elements in Mendeleev's periodic table.
6. 6. Mendeleev’s periodic table is based on _________?
Mendeleev’s periodic table is based on the atomic mass.
7. What are the main characteristics of Mendeleev's Periodic Table?
The main characteristics include: arrangement by increasing atomic weight, grouping of elements with similar properties, gaps left for undiscovered elements, and the ability to predict properties of unknown elements.
8. What is the concept of periodicity in Mendeleev's table?
Periodicity refers to the recurring patterns of properties observed in elements as their atomic weights increase. Mendeleev noticed that elements with similar properties appeared at regular intervals, forming a periodic pattern.
9. How did Mendeleev's table handle elements with very similar atomic weights?
In cases where elements had very similar atomic weights, Mendeleev sometimes placed them based on their chemical properties rather than strictly by weight. This occasionally led to inversions in the order of elements.
10. How did Mendeleev's table compare to other classification attempts of his time?
Mendeleev's table was more comprehensive and predictive than other attempts. While others like Newlands and Meyer made important contributions, Mendeleev's work was the most successful in organizing all known elements and predicting new ones.
11. What is the significance of Mendeleev's prediction of "eka-elements"?
Mendeleev predicted the properties of several undiscovered elements, which he called "eka-elements" (eka meaning "one" in Sanskrit). The accurate prediction and subsequent discovery of these elements (like eka-silicon, now known as germanium) validated his periodic law.
12. How does Mendeleev's table differ from the modern periodic table?
Mendeleev's table was based on atomic weight, while the modern table is based on atomic number. The modern table also includes elements discovered after Mendeleev's time and has a more accurate arrangement of elements.
13. How did Mendeleev's Periodic Table handle the noble gases?
Mendeleev's original table did not include noble gases, as they were not discovered until later. When they were discovered, they were initially difficult to place in the existing structure, leading to revisions in the table.
14. How did Mendeleev's table handle isotopes?
Mendeleev's table did not account for isotopes, as they were unknown at the time. This sometimes led to inconsistencies in the ordering of elements based solely on atomic weight.
15. How did Mendeleev's table handle the placement of hydrogen?
Mendeleev struggled with the placement of hydrogen, as it shared properties with both alkali metals and halogens. This difficulty in classifying hydrogen persists even in the modern periodic table.
16. How did Mendeleev's table deal with elements that were later discovered to be compounds?
In some cases, Mendeleev included substances that were later found to be compounds rather than elements. As these were identified, they were removed from the table, refining its accuracy.
17. What is the Mendeleev Periodic Table?
The Mendeleev Periodic Table is a systematic arrangement of chemical elements, created by Russian chemist Dmitri Mendeleev in 1869. It organizes elements based on their atomic weights and chemical properties, allowing for the prediction of undiscovered elements and their properties.
18. How did Mendeleev's table handle the concept of atomic structure?
Mendeleev's table predated the discovery of atomic structure. However, its organization hinted at an underlying structure of atoms, which was later confirmed with the discovery of electrons, protons, and neutrons.
19. How did Mendeleev's table contribute to the understanding of element families?
Mendeleev's arrangement clearly showed families of elements with similar properties (like halogens and alkali metals). This grouping helped chemists understand and predict chemical behavior across element families.
20. How did Mendeleev's table contribute to the understanding of chemical bonding?
While Mendeleev didn't explicitly address chemical bonding, his arrangement of elements based on their properties laid the groundwork for later theories of chemical bonding, especially in understanding valence electrons.
21. What was the significance of Mendeleev's use of question marks in his table?
Mendeleev used question marks to indicate uncertainty about the properties or existence of some elements. This demonstrated the predictive nature of his table and encouraged further research to fill these gaps.
22. How did Mendeleev's Periodic Table contribute to the discovery of new elements?
Mendeleev's table predicted the existence and properties of several unknown elements. This guided scientists in their search for these elements, leading to the discovery of gallium, scandium, and germanium, among others.
23. What is the significance of the gaps in Mendeleev's Periodic Table?
The gaps in Mendeleev's table represented undiscovered elements. By leaving these gaps, Mendeleev correctly predicted the existence and properties of elements that were later discovered, demonstrating the predictive power of his arrangement.
24. What was revolutionary about Mendeleev's approach to element classification?
Mendeleev's approach was revolutionary because it was the first to successfully predict the properties of undiscovered elements and provide a comprehensive framework for organizing all known elements based on their properties.
25. How did Mendeleev's table help in correcting the atomic weights of some elements?
When elements didn't fit the pattern based on their accepted atomic weights, Mendeleev suggested that their atomic weights might be incorrect. In several cases, subsequent research proved him right, leading to corrections in atomic weight measurements.
26. What role did valency play in Mendeleev's classification?
Valency, or the combining power of elements, was an important factor in Mendeleev's classification. He grouped elements with similar valencies together, which helped in predicting the properties of unknown elements.
27. How did Mendeleev's work influence the development of atomic theory?
Mendeleev's work suggested that elements had some underlying structure that caused their properties to repeat periodically. This idea contributed to the development of atomic theory and the discovery of subatomic particles.
28. What was the impact of Mendeleev's Periodic Table on the field of chemistry?
Mendeleev's table had a profound impact on chemistry. It provided a systematic way to organize elements, predict new ones, and understand chemical behavior. It became the foundation for modern atomic theory and chemical research.
29. What was the relationship between Mendeleev's Periodic Table and the concept of atomic number?
Mendeleev's table was not based on atomic number, as this concept was unknown at the time. However, his arrangement closely approximated the order of increasing atomic number, which later became the basis for the modern periodic table.
30. What was the significance of Mendeleev's use of vertical columns in his table?
The vertical columns in Mendeleev's table, now known as groups, contained elements with similar chemical properties. This vertical arrangement highlighted the periodic nature of element properties and became a key feature of the periodic table.
31. What was the significance of Mendeleev's use of atomic weight ratios?
Mendeleev observed that the atomic weights of elements in the same group often formed simple ratios. This observation helped him predict the atomic weights of undiscovered elements and refine the weights of known elements.
32. How did Mendeleev arrange elements in his periodic table?
Mendeleev arranged elements in order of increasing atomic weight, grouping them into rows and columns based on similar chemical properties. He left gaps for undiscovered elements and even predicted their properties accurately.
33. What was the primary basis for Mendeleev's classification of elements?
The primary basis for Mendeleev's classification was the atomic weight of elements and their chemical properties. He observed that elements with similar properties appeared at regular intervals when arranged by increasing atomic weight.
34. What are triads in Mendeleev's Periodic Table?
Triads are groups of three elements with similar properties where the atomic weight of the middle element is approximately the average of the other two. This concept, developed earlier by Johann Döbereiner, influenced Mendeleev's work.
35. What is the Law of Octaves, and how did it influence Mendeleev's work?
The Law of Octaves, proposed by John Newlands, stated that every eighth element had similar properties when elements were arranged by atomic weight. This idea influenced Mendeleev's thinking about periodicity in element properties.
36. How did Mendeleev's table account for the relationship between atomic weight and atomic volume?
Mendeleev observed that atomic volume generally increased down a group and varied periodically across periods. This relationship helped him in arranging elements and predicting properties of unknown elements.
37. How did Mendeleev's table handle the lanthanides and actinides?
Mendeleev's original table did not separately classify lanthanides and actinides. As more of these elements were discovered, they posed a challenge to the table's structure, leading to later modifications in the periodic table design.
38. What were some of the main drawbacks of Mendeleev's Periodic Table?
Main drawbacks included: basing the arrangement on atomic weight instead of atomic number, difficulty in placing hydrogen and noble gases, and inability to explain the similarities between some elements in different groups.
39. What was the role of chemical formulas in Mendeleev's classification system?
Mendeleev used chemical formulas to identify similarities in the combining ratios of elements. This helped him group elements with similar chemical behaviors together, reinforcing the periodic patterns in his table.
40. How did Mendeleev's table handle elements with multiple valencies?
For elements with multiple valencies, Mendeleev typically used the highest known valency to determine their position in the table. This sometimes led to inconsistencies but generally worked well for most elements.
41. How did Mendeleev's table handle the transition metals?
Mendeleev placed transition metals in the center of his table, recognizing their distinct properties. However, the full complexity of transition metal chemistry was not fully understood at the time, leading to some inconsistencies in their arrangement.
42. What role did oxidation states play in Mendeleev's classification?
Mendeleev used the concept of oxidation states (though not termed as such then) to help arrange elements. Elements with similar maximum oxidation states were often grouped together, contributing to the table's organization.
43. How did Mendeleev's table handle elements that were later found to be mixtures of isotopes?
Mendeleev's table couldn't account for isotopes, as they were unknown at the time. The discovery of isotopes later explained some of the inconsistencies in Mendeleev's arrangement based on atomic weights.
44. What was the impact of Mendeleev's work on the field of spectroscopy?
Mendeleev's predictions encouraged spectroscopists to search for specific spectral lines of predicted elements. This led to the discovery of several elements, validating Mendeleev's work and advancing spectroscopic techniques.
45. What was the relationship between Mendeleev's work and the development of quantum mechanics?
While Mendeleev's work predated quantum mechanics, his periodic law laid the foundation for understanding electron configurations. The periodicity he observed was later explained by quantum mechanical principles.
46. How did Mendeleev's table contribute to the understanding of chemical reactions?
By grouping elements with similar properties, Mendeleev's table allowed chemists to predict and understand chemical reactions better. Elements in the same group often underwent similar reactions, providing a framework for studying chemical behavior.
47. What was the significance of Mendeleev's use of horizontal rows in his table?
The horizontal rows, now known as periods, showed the gradual change in properties as atomic weight increased. This arrangement highlighted the periodic nature of element properties and became fundamental to understanding elemental trends.
48. How did Mendeleev's work influence the development of inorganic nomenclature?
Mendeleev's systematic arrangement of elements influenced the development of systematic naming conventions in inorganic chemistry, particularly in naming compounds based on the position of elements in the periodic table.
49. What was the impact of Mendeleev's Periodic Table on the field of metallurgy?
Mendeleev's table helped metallurgists understand the properties of metals and their alloys better. It provided a framework for predicting the behavior of metal combinations and guided the search for new useful alloys.
50. How did Mendeleev's table handle the concept of electronegativity?
While electronegativity wasn't a defined concept during Mendeleev's time, his arrangement of elements inadvertently grouped elements with similar electronegativity together, laying groundwork for later understanding of this property.
51. What was the significance of Mendeleev's use of atomic volume in his classification?
Mendeleev observed that atomic volume varied periodically with atomic weight. This observation helped him in arranging elements and predicting properties of unknown elements, contributing to the periodic law.
52. How did Mendeleev's table contribute to the understanding of element abundance in nature?
While not a primary focus, Mendeleev's table helped in understanding element abundance patterns. Elements in odd-numbered columns (in his arrangement) were generally found to be more abundant in nature.
53. What was the relationship between Mendeleev's work and the later discovery of nuclear structure?
Mendeleev's work predated the understanding of nuclear structure. However, the periodicity he observed was later explained by nuclear structure and electron configurations, validating his approach from a more fundamental perspective.
54. How did Mendeleev's table handle the concept of ionization energy?
While ionization energy wasn't known during Mendeleev's time, his arrangement of elements roughly corresponded to periodic trends in ionization energy, which were later discovered and explained by atomic structure.
55. What was the impact of Mendeleev's Periodic Table on the development of analytical chemistry?
Mendeleev's table provided a systematic framework for understanding element properties, which greatly aided the development of analytical techniques. It helped in predicting chemical behavior and designing separation methods.
56. How did Mendeleev's work contribute to the understanding of periodic trends in element properties?
Mendeleev's arrangement revealed periodic patterns in properties like atomic size, melting point, and reactivity. While he couldn't explain these trends fully, his work laid the foundation for understanding periodic trends in element properties across the table.
