Question 5 - Case Based Questions (MCQ) - Chapter 3 Class 10 - Metals and Non-Metals

Read the given passage and answer any four  questions from (a) to (e).  

Metallic Character:  The ability of an atom to donate electrons and form a positive ion (cation) is known as electro-positivity  or metallic character. Down the group, metallic  character increases due to increase in atomic size  and across the period, from left to right electropositivity decreases due to decrease in atomic size.  

Non-Metallic Character:  The ability of an atom to accept electrons to form  a negative ion (anion) is called non-metallic  character or electronegativity. The elements having  high electro-negativity have a higher tendency to gain electrons and form anion.  Down the group, electronegativity decreases due  to increase in atomic size and across the period,  from left to right electro -negativity increases due  to decrease in atomic size.

(a) Which of the following correctly represents the  decreasing order of metallic character of Alkali  metals plotted in the graph?  

(i) Cs>Rb>Li>Na>K 

(ii) K>Rb>Li>Na>Cs  

(iii) Cs>Rb>K>Na>Li 

(iv) Cs>K>Rb>Na>Li  

Answer 

As we go down the group , atomic size increases and the ability to donate electrons, i.e. electropositivity increases . So, the metallic character also increases.

The order of increasing atomic size is as follows: Cs>Rb>K>Na>Li

So, the correct option is (iii) 

(b) Hydrogen is placed along with Alkali metals in  the modern periodic table though it shows nonmetallic character:  

(i) as Hydrogen has one electron & readily loses electrons to form negative ions.  

(ii) as Hydrogen can easily lose one electron like  alkali metals to form a positive ion.  

(iii) as Hydrogen can gain one electron easily like  Halogens to form a negative ion.  

(iv) as Hydrogen shows the properties of nonmetals.  

Answer 

Alkali metals lose one electron to form a positive ion.

Hydrogen also loses its one electron to form H +

So, the correct answer is (ii) 

(c) Which of the following has the highest  electronegativity?

(i) F 

(ii) Cl  

(iii) Br 

(iv) I 

Answer

• Electronegativity decreases  as we go down the group. 
• The order of electronegativity can be given as: F>Cl>Br>I

So, the correct answer is (i) 

(d) Identify the reason for the gradual change in  electronegativity in halogens down the group.  

(i) Electronegativity increases down the group due  to decrease in atomic size.  

(ii) Electronegativity decreases down the group  due to decrease in tendency to lose electrons.  

(iii) Electronegativity decreases down the group  due to increase in atomic radius/ tendency to  gain electron decreases.  

(iv) Electronegativity increases down the group  due to increase in forces of attractions between  nucleus & valence electrons.  

Answer 

• Electronegativity decreases down the group due to an increase in atomic radius. 
• It leads to a decrease in the force of attraction between valence electrons and nucleus.  
• So, the tendency to gain electrons decreases . 

So, the correct answer is (III) 

(e) Which of the following reasons correctly justifies  that “Fluorine (72pm) has a smaller atomic radius  than Lithium (152pm)”? 

(i) F and Li are in the same group. Atomic size  increases down the group  

(ii) F and Li are in the same period. Atomic size  increases across the period due to increase in  number of shells  

(iii) F and Li are in the same group. Atomic size  decreases down the group  

(iv) F and Li are in the same period and across the  period atomic size/radius decreases from left  to right.  

Answer

• F and Li are in the same period 
• Atomic size/radius decreases from left to  right. 

So, the correct answer is (III)