Question

Question 3.33 In the modern periodic table, the period indicates the value of:

(a) Atomic number

(b) Atomic mass

(c) Principal quantum number

(d) Azimuthal quantum number.

Class XI Classification of Elements and Periodicity in Properties Page 94

Answer 1

In the modern periodic table, the period indicates the value of principle quantum number.
Down the group,principal quantum number i.e. number of shells increases while it remains fixed for particular period. All the elements of period 3 would have 3 shells thus n = 3.

Answer 2

in morden periodic table, the period indicates the value of principal quantum number.
Let see example : Na, configuration of Na = 1s², 2s², 2p⁶, 3s¹

hence, electron enters 3s , it means principal quantum number = 3 e.g., position of Na in period is 3rd.

e.g., option ( c ) is correct answer.