CBSE Class 10 Chemistry Case Study Questions Periodic Classification of Elements MCQs

Case/Passage – 1
Metallic Character The ability of an atom to donate electrons and form positive ion (cation) is known as electropositivity or metallic character. Down the group, metallic character increases due to increase in atomic size and across the period, from left to rightelectropositivity decreases due to decreasein 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 electronegativity increases due to decrease in atomic size.

Question. Hydrogen is placed along with Alkali metals in the modern periodic table though it shows non-metallic character
(a) as Hydrogen has one electron & readily loses electron to form negative ion 
(b) as Hydrogen can easily lose  one electron like alkali metals to form positive ion 
(c) as Hydrogen can gain one electron easily like Halogens to form negative ion
(d) as Hydrogen shows the properties of non-metals     

Answer: B

Question. Which of the following has highest electronegativity? 
(a) F
(b) Cl
(c) Br
(d) I   

Answer: A

Question. Which of the following correctly represents the decreasing order of metallic character of Alkali metals plotted in the graph?
(a) Cs > Rb > Li > Na > K
(b) K > Rb > Li > Na > Cs
(c) Cs > Rb > K > Na > Li
(d) Cs > K > Rb > Na > Li   

Answer: C

Question. Which of the following reason correctly justifies that “Fluorine (72pm) has smaller atomic radius than Lithium (152pm)”?
(a) F and Li are in the same group. Atomic size increases down the group
(b) F and Li are in the same period. Atomic size increases across the period due to increase in number of shells
(c) F and Li are in the same group. Atomic size decreases down the group
(d) F and Li are in the same period and across the period atomic size/radius decreases from left to right.

Answer: D

Question. Identify the reason for the gradual change in electronegativity in halogens down the group. 
(a) Electronegativity increases down the group due to decrease in atomic size
(b) Electronegativity decreases down the group due to decrease in tendency to lose electrons
(c) Electronegativity decreases down the group due to increase in atomic radius/ tendency to gain electron decreases
(d) Electronegativity increases down the group due to increase in forces of attractions between nucleus & valence electrons 

Answer: C

Case/Passage – 2
The table given below refers to the elements of the periodic table with atomic number from 3 to 18. These elements are shown by letters. (not by the usual symbols of the elements).

Question. Which of the following are noble gases?
(a) H and P
(b) G and O
(c) D and L
(d) A and I 

Answer: A

Question. Which of the following elements have valency 4?
(a) F and N
(b) C and K
(c) D and L
(d) H and P 

Answer: C

Question. Which are halogens?
(a) H and L
(b) C and M
(c) G and O
(d) E and P   

Answer: C

Case/Passage – 3
Group VII A elements are strong non-metals because they can easily accept an electron to form an anion whereas group 1 A element are strong metals because they can very easily lose one electron to form cation. Metals have the tendency to lose their valence electrons and form positive ions, so metallic character is related to the ionisation potential. Elements having low ionisation potential, lose electrons easily. Thus, metallic character generally decreases across a period and increases down a group. 

Question. Group 1 and group 2 elements are considered as strong metals because
(a) they have incomplete octet.
(b) they can easily gain electrons.
(c) they can easily lose electrons.
(d) they form anions.   

Answer: C

Question. Which of the following is the correct decreasing order of metallic character?
(a) Ca > Sc > Ti > K
(b) K > Ca > Sc > Ti
(c) K > Sc > Ca > Ti
(d) Ti > Sc > Ca > K 

Answer: B

Question. The non metallic character on moving along a period –
(a) increases
(b) decreases
(c) depends on the period
(d) remains the same   

Answer: A

Case/Passage – 4
Around the year 1800, only 30 elements were known. Dobereiner in 1817 and Newlands in 1866 tried to arrange the then known elements and framed laws which were rejected by the scientists. Even after the rejection of the proposed laws, many scientists continued to search for a pattern that correlated the properties of elements with their atomic masses.
The main credit for classifying elements goes to Mendeleev for his most important contribution to the early development of a Periodic table of elements wherein he arranged the elements on the basis of their fundamental property, the atomic mass and also on the similarity of chemical properties. The formulae of their hydrides and oxides were treated as basic criteria for the classification of the elements. However, Mendeleev’s classification also had some limitations as it could not assign the position to isotopes. He also left some gaps in the periodic table.

Question. If the letter ‘R’ was used to represent any of the elements in the group, then the hydride and oxide of carbon would respectively be represented as
(a) RH4, RO
(b) RH4, RO2
(c) RH2, RO2
(d) RH2, RO

Answer: B

Question. Isotopes are:
(a) Atoms of an element with similar chemical properties but different atomic masses. 
(b) Atoms of different elements with similar chemical properties but different atomic masses.
(c) Atoms of an element with different chemical properties but same atomic masses.
(d) Atoms of different elements with different chemical properties but same atomic masses.

Answer: A

Question. How many groups and periods are there in Mandeleev’s periodic table?
(a) 6 group, 8 period
(b) 18 group, 7 period
(c) 7 group, 18 period
(d) 8 group, 6 period

Answer: D

Question. According to Mendeleev’s Periodic Law properties of elements are periodic function of
(a) atomic mass
(b) atomic number
(c) number of protons
(d) number of electrons

Answer: A

Question. Why did Mendeleev leave some gaps in the Periodic table?
(a) For elements to be discovered
(b) For isotopes
(c) For isobars
(d) None of these

Answer: A

Case/Passage – 5
Modern periodic table has 18 vertical columns known as groups and 7 horizontal rows known as periods. First period contains 2 elements second and third period contain 8 elements. 4th and 5th period contains 18 elements and 6th and 7th period contains 32 elements. The graph is plotted between atomic number and atomic radius of group 17 and group 1 elements.

Question. What happens to atomic radii in a group from top to bottom?
(a) Increases
(b) Decreases
(c) First decreases then increases
(d) Number of shells remains the same

Answer: A

Question. Atomic size decreases from left to right in a period because
(a) Effective nuclear charge increases
(b) Number of shells remains the same
(c) Force of attraction between the nucleus and valence electrons increases
(d) All of these

Answer: D

Question. Which group elements will have largest atomic size?
(a) Group 1
(b) Group 2
(c) Group 3
(d) Group 18

Answer: A

Question. Which group elements will gain electrons to form negative ions?
(a) Group 1
(b) Group 2
(c) Group 17
(d) Group 18

Answer: C

Question. Which element in group 17 has smallest size?
(a) Flourine
(b) Bromine
(c) Chlorine
(d) Iodine

Answer: A

Case/Passage – 6

Question. How electronegativity varies in a period?
(a) Increases from left to right
(b) Decreases from left to right
(c) First increases then decreases
(d) Vary independently

Answer: A

Question. What happens to tendency to gain electron in a period?
(a) Increases,
(b) Decreases,
(c) Remaining same,
(d) First increases then decreases.

Answer: A

Question. How electronegativity varies in a period?
(a) Increases down the group
(b) Decreasing down the group
(c) First increases then decreases down the group
(d) Vary independently

Answer: B

Question. Which of the following has least electronegativity?
(a) Li,
(b) Be,
(c) O,
(d) N

Answer: A

Question. Which element has highest electronegativity?
(a) C
(b) N
(c) O
(d) F

Answer: D

Case/Passage – 7
numbers 1 – 3 are based on the periodic table. Study the part of the modern periodic table presented below in which the alphabets represent the symbols of elements and answer the following questions. 

Question. Consult the above part of the periodic table to predict which of the given combination is a covalent compound:
RQ2, AT, JQ, JX2.       
Answer: R and Q are members of group 16th having elements,O, S, Se, Te etc. RQ2 is characterised by showing the formation of covalent bond.

Question. Which of the given element is the most electronegative element?    
Answer: Element ‘V’ is the most electronegative element

Question. Considering the above part of the periodic table, which of the given element is the most electropositive element?    
Answer: Element ‘G’ is the most electropositive element.

Question. Study the data of the following three categories A, B and C.

(i) From the given three categories A, B and C, Pick the one which forms Dobereiner’s Triads.
(ii) Why did Mendeleev placed elements of category A, B and C in three different groups?
(iii) Is Newland law of octaves applicable to all the three categories?
Give reason to justify your answer.
Answer: (i) Dobereiner’s Triads is A.
(ii) Mendeleev placed elements of category A,B and C 
in three different groups because they have different physical and chemical properties.
(iii) No, Newland’s Law of octaves is not applicable for all three categories.
Because the law of octaves states that every eighth element has similar properties when the elements are arranged in the increasing order of their atomic masses.