Question
Question: What is the atomic number of last member of the seventh period of the extended form of periodic tabl...
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
Answer
118
Explanation
Solution
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.