JEE Main 2021 · 22 July · evening · Single correct · +4 / −1
Which one of the following statements for D.I. Mendeleeff, is incorrect?
- (a) He authored the textbook - Principles of Chemistry
- (b) At the time, he proposed Periodic Table of elements structure of atom was known.
- (c) Element with atomic number 101 is named after him.
- (d) He invented accurate barometer.
Answer and solution
Answer (b) At the time, he proposed Periodic Table of elements structure of atom was known.
Solution
Chemistry ma’am · 3 steps
Check the dates: Mendeleev's table came in 1869, decades before anyone knew what was inside an atom.
- The timeline. Mendeleev published his periodic table in 1869. The electron was discovered in 1897, the nucleus in 1911, and Moseley linked properties to atomic number in 1913.
Statement True or false Why (a) Wrote Principles of Chemistry True His textbook, written in 1868 to 1871, while he was building the table (b) Atomic structure was known in his time False He arranged elements by atomic mass, because atomic structure was not yet known (c) Element 101 is named after him True Element 101 is mendelevium, Md (d) Invented an accurate barometer True He designed a precise barometer while studying gases - Why it matters. Not knowing atomic structure is exactly why his table had flaws. Pairs like Ar and K had to be placed against the order of their atomic masses. The Modern Periodic Law fixed this by using atomic number.
- So. The incorrect statement is (b). Atomic structure was not known when Mendeleev proposed his periodic table.
The idea to keep. Mendeleev's law was based on atomic mass because atomic structure was unknown in 1869. Atomic number as the basis came later with Moseley, and that is the Modern Periodic Law.
Answer from the NTA final answer key. Solution by PrepWiser.