Answer :
(a) The symbol, group number, and period number of the element is, Cd, 12 and 5 respectively.
(b) The symbol, group number, and period number of the element is, Ni, 10 and 4 respectively.
Explanation :
Electronic configuration : It is defined as the representation of electrons around the nucleus of an atom.
Number of electrons in an atom are determined by the electronic configuration.
To identify the block of the element after you get its electronic configuration:
(i) If the element belongs to s-block.
Group number = Number of valence electrons (or outermost shell electrons).
(ii) If the element belongs to p- block.
Group number = No. of valence electrons + 10 .i.e., 10 + np electrons + ns electrons.
(iii) If the element belongs to d-block.
Group no. = no. of electrons in (n-1) d subshell + no. of electron/s in ns shell.
(iv) If the element belongs to f-block, Group no. = 3.
(a) [Kr] 5s²4d¹⁰
From the given electronic configuration, we conclude that it has 12 valence electrons and belongs to d-block. So, it belongs to group number 12 (2+10).
The highest energy level in the electronic configuration shows the period number. In this, highest energy level is (n=5). So, the period number is, 5.
Thus, the element which is present in 5th period and 12th group number is, cadmium (Cd).
(b) [Ne] 4s²3d⁸
From the given electronic configuration, we conclude that it has 10 valence electrons and belongs to d-block. So, it belongs to group number 10 (2+8).
The highest energy level in the electronic configuration shows the period number. In this, highest energy level is (n=4). So, the period number is, 4.
Thus, the element which is present in 4th period and 10th group number is, nickel (Ni).
