Answer :
(a) The symbol, group number, and period number of the element is, O, 16 and 2 respectively.
(b) The symbol, group number, and period number of the element is, P, 15 and 3 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) [He] 2s²2p⁴
From the given electronic configuration, we conclude that it has 6 valence electrons and belongs to p-block. So, it belongs to group number 16 (6+10).
The highest energy level in the electronic configuration shows the period number. In this, highest energy level is (n=2). So, the period number is, 2.
Thus, the element which is present in 2nd period and 16 group number is, oxygen (O).
(b) [Ne] 3s²3p³
From the given electronic configuration, we conclude that it has 5 valence electrons and belongs to p-block. So, it belongs to group number 15 (5+10).
The highest energy level in the electronic configuration shows the period number. In this, highest energy level is (n=3). So, the period number is, 3.
Thus, the element which is present in 3rd period and 15 group number is, phosphorous (P).
