Chemistry Classification of Elements and Periodicity Development of Periodic Table, Period, Group and Block Single Correct MCQ
Published on: August 14, 2026

What is the atomic number of last member of the seventh period of the extended form of periodic table?

A
116
B
118
C
120
D
122

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Text Solution

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The correct answer is:
B

the las member of the sixth period is radon. its atomic number is 86. In the seventh period energy shells 7s, 5f, 6d and 7p are completed , i.e. 2 + 14 + 10 + 6 = 32 electrons are to be accommodated. Thus,in the 7th period, 32 elements will be present. So, the atomic number of the last member will be 86 + 32 = 118.

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