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  • (c) Which of the elements whose atomic numbers are given below, cannot be accommodated in the present set up of the long form of the periodic table? (i) 107 (ii) 118 (iii) 126 (iv) 102

Comprehension given below is followed by some multiple choice questions. Each question has one correct option. Choose the correct option. In the modern periodic table, elements are arranged in order of increasing atomic numbers which is related to the electronic configuration. Depending upon the type of orbitals receiving the last electron, the elements in the periodic table have been divided into four blocks, viz, s, p, d and f. The modern periodic table consists of 7 periods and 18 groups. Each period begins with the filling of a new energy shell. In accordance with the Aufbau principle, the seven periods (1 to 7) have 2, 8, 8, 18, 18, 32 and 32 elements respectively. The seventh period is still incomplete. To avoid the periodic table being too long, the two series of f-block elements, called lanthanoids and actinoids are placed at the bottom of the main body of the periodic table.

 (c) Which of the elements whose atomic numbers are given below, cannot be accommodated in the present set up of the long form of the periodic table?

(i) 107

 (ii) 118

 (iii) 126

 (iv) 102

Answers (1)

The answer is the option (iii) 126

 Explanation: In the present set up of the long form of the periodic table, there are seven periods and four blocks. So, the maximum number of elements according to the Aufbau principle, which can be accommodated in the present set up of the periodic table is  118.

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