Devendra was told that the elements `P,Q` and `R` belong to group 2 , group 14 and group 17, respectivelhy, of the long form of periodic table. Based on this information, he was asked to answer the following questions:
(a) What is the valency of (i) element `P` (ii) element `Q` and (iii) element `R`? Give reasons for your answer.
(b) What is nature of oxide of (i) element `P` (ii) element `Q` and (iii) element `R`? Give reasons for your answer.
(c) Give one example each of (i) element `P` (ii) element `Q` and (iii) element `R`.
(d) Name three elements which occur in the same group as element `R` but exist in three different physical states at room temperature.
(e) What values are displayed by Devendra in answering these question?

Explanation

(a) (i) The valency of element `P` is 2. This can be explained as follows.The elements of group 2 of periodic table have 2 valence electrons each in their atoms. So, the atom of this element can lose 2 valence electrons (to some other atom), to attain the nearest inert gas electron configuration and hence shows a valency of 2.
(ii) The valency of element `Q` is 4. This can be explaine as follows: The elements of group 14 of periodic table have `14-10=14` valence electrons each in theri atoms. An atom of his element can share its 4 valence electrons with 4 more electrons to achieve the nearest inert gas electron configuration and hence shows a valency of 4.
(iii) The valencey of element `R` is 1. This can be explained as follows: The elements of group 17 of periodic table have `17-10=7` valence electrons each in their atoms. An atom of this element having 7 valence electrons can accept 1 more electron to complete the stable, inert gas electron configuration and hence shows a valency of 1.
(b) (i) The elements of group 2 of periodic table are metals.Now,metals form basic oxides. So, the nature of oxide of element `P` is basic.
(ii) The elements of group 14 of periodic table are non-metals. Now, non-metals form acidic oxides. So, the nature of oxide of element `O` is acidic.
(iii) The elements of group 17 of periodic table are also non-metals. Now, non-metals form acidic oxides. So, the nature of oxide of element `R` is acidic.
(c) (i) An example of element `P` of group 2 is magnesium (`Mg`)
(ii) An example of element `Q` of group 14 is carbon `(C)`.
(iii) An example of element `R` of group 17 is chlorine `(Cl)`.
(d) Element `R` occurs in group 17 of periodic table which compirses halogen elements. So, in group 17 of periodic table:
(i) iodine is a solid element.
(ii) bromine is liquid element, and
(iii) chlorine is a gaseous element.
(e) The various values displayed by Devendra in answering these questions are (i) Knowledge of the characteristics of groups of the periodic table, and (ii) Application of knowledge in solving problems.