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NEET Exam  >  NEET Questions  >  Which of the following element was not presen... Start Learning for Free
Which of the following element was not present in Mendeleev's Periodic Table?
  • a)
    rubidium
  • b)
    cesium
  • c)
    francium
  • d)
    uranium
Correct answer is option 'C'. Can you explain this answer?
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Verified Answer
Which of the following element was not present in Mendeleev's Periodic...
When Mendeleev first proposed his periodic table in 1869 he left gaps for elements not yet discovered, but that he predicted should exist. One such gap was one beneath caesium, a position later found to belong to francium. Francium, number 87, was the last of these elements to be discovered in nature.
Origin of the name: Francium was named for France, the country of its discovery.
Discovered by: Marguerite Perey

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Which of the following element was not present in Mendeleev's Periodic...
Introduction:

In Mendeleev's Periodic Table, several elements were missing, as the table was not yet complete. One of the elements that was not present in Mendeleev's Periodic Table is francium.

Explanation:

Mendeleev's Periodic Table, proposed in 1869, was one of the first attempts to organize the known elements based on their chemical and physical properties. However, at that time, several elements had not yet been discovered or accurately characterized. Francium, in particular, was not discovered until 1939, several decades after Mendeleev's Periodic Table was introduced.

Properties of Francium:

- Francium is a highly radioactive alkali metal.
- It is the second rarest naturally occurring element in the Earth's crust.
- Francium is the most unstable of the first 101 elements, with a half-life of only a few minutes.
- Due to its high reactivity and short half-life, francium is extremely difficult to isolate and study.

Placement of Francium in the Modern Periodic Table:

In the modern periodic table, francium is placed in the alkali metal group (Group 1) along with elements such as lithium, sodium, and potassium. It is located below cesium (Cs) and rubidium (Rb) in the same group. Francium has the atomic number 87 and its symbol is Fr.

Significance of Mendeleev's Periodic Table:

Although Mendeleev's Periodic Table was incomplete and did not include elements like francium, it laid the foundation for the development of the modern periodic table. Mendeleev's approach of arranging elements based on their properties and leaving gaps for undiscovered elements allowed for the prediction of properties of yet-to-be-discovered elements. This predictive power of the periodic table was later confirmed when francium was discovered and found to exhibit similar characteristics to other alkali metals.

Conclusion:

In conclusion, francium was not present in Mendeleev's Periodic Table as it had not yet been discovered at the time. However, the modern periodic table includes francium in the alkali metal group, following the principles established by Mendeleev's Periodic Table.
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Read the passage given below and answer the following questions:The d block elements are the 40 elements contained in the four rows of ten columns (3-12) in the periodic table. As all the d block elements are metallic, the term d-block metals is synonymous. This set of d-block elements is also often identified as the transition metals, but sometimes the group 12 elements (zinc, cadmium, mercury) are excluded from the transition metals as the transition elements are defined as those with partly filled d or f shells in their compounds. Inclusion of the elements zinc, cadmium and mercury is necessary as some properties of the group 12 elements are appropriate logically to include with a discussion of transition metal chemistry. The term transition element or transition metal appeared to derive from early studies of periodicity such as the Mendeleev periodic table of the elements. His horizontal table of the elements was an attempt to group the elements together so that the chemistry of elements might be explained and predicted. In this table there are eight groups labeled I-VIII with each subdivided into A and B subgroups. Mendeleev recognized that certain properties of elements in Group VIII are related to those of some of the elements in Group VII and those at the start of the next row Group I. In that sense, these elements might be described as possessing properties transitional from one row of the table to the next.In the following questions, a statement of assertion followed by a statement of reason is given. Choose the correct answer out of the following choices on the basis of the above passage.Assertion (

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Which of the following element was not present in Mendeleev's Periodic Table?a) rubidium b) cesium c) francium d) uranium Correct answer is option 'C'. Can you explain this answer?
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