Q28 of 49 Page 145

The position of five elements in the periodic table are shown below:


What are the number of valence electrons in B?


Identify the element(s) which


(i) will have the smallest atomic radius?


(ii) will be the most metallic?


(iii) will form basic oxide?


(iv) will show valency three?


(v) will show greatest tendency to gain electron?

Since, we know that elements in 16th group have 6 electrons in their outer most shell i.e. the valence electrons are 6. Therefore, we can say that B has 6 valence electrons.


(Note: For this case ignore the period.)


(i) We know that element in lower period have smaller radius as compared other as they have less no. of shells. Also, going along period the size of atom decreases as the effective nuclear charge on outer electrons increases. So, B will have smallest size as it lies in 1st period and 16th group.


(ii) We know that, the metallic character increases going down the group and decreases going right along the period. Thus C will be most metallic of all.


(iii) Since C and A lie in 1st and 2nd group so these can readily lose electron and thus can form basic oxides.


(iv) We know that elements of 15th group need only three electrons to complete their octet configuration and thus show valency 3. So, D will show valency 3.


(v) We know that tendency to gain electron or electron gain enthalpy increases going right along period and decreases going down the group. Thus, B will show highest tendency to gain electrons


More from this chapter

All 49 →
26

X is an element with atomic number 20.

(i) Is it a metal or a non-metal?


(ii) Among X or Mg, which one is more reactive?


(iii) What is the valency of X?

 27

X is an element of modern periodic table. It is surrounded by elements having atomic number 17, 34, 36 and 53.

(i) What is the atomic number of X?


(ii) Predict its position in the periodic table.


(iii) Which among these do not belong the same period?

 29

A non-metal A which is the largest constituent of air combines with hydrogen on heating in the presence of Fe (as catalyst) and forms a gas

B. When this gas B is treated with H2SO4, compound C is formed which is broadly used as chemical fertiliser.


(i) Identify A, B and C.


(ii) Locate the position of A in the modern periodic table.


(iii) Which elements are present before and after the element A?


(iv) Write the electronic configuration of element A.

 30

A teacher of Xth class, during teaching explains the importance of the music in our daily life. She was telling to her students that in the Indian system of music, there are seven musical notes in a scale sa, re, ga, ma, pa, da, ni. And in the west notations used are do, re, mi, fa, so, la, ti. The notes in a scale are separated by whole frequency intervals of tones. Every eighth note is similar to the first one and it is first note of next scale. A musician use these notes for composing music of a song.

Read the above passage carefully and answer the following questions accordingly.


(i) Is the situation discussed above is similar to something in chemistry? Explain.


(ii) What are the limitations of the above principle in case of chemistry?


(iii) What are the values you will infer from above passage?