In This Post we are providing Chapter-4 THE p-BLOCK ELEMENT NCERT MOST IMPORTANT QUESTIONS for Class 11 CHEMISTRY which will be beneficial for students. These solutions are updated according to 2021-22 syllabus. These MCQS can be really helpful in the preparation of Board exams and will provide you with a brief knowledge of the chapter.
NCERT MOST IMPORTANT QUESTIONS ON THE p-BLOCK ELEMENT
1.Why the elements of group 13 are called p-block elements?
Ans.Group 13 elements are called p-block elements because the last electron is present in the p-orbital (np1). The valence shell configurations are B (2s2 2p1), Al (3s2, 3p1), Ga (4s2, 4p1), In (5s2 5p1) Tl (6s2 6p1)
2.The elements B, Al, Ca, In and Tl are placed in the same group of the periodic table. Give reason.
Ans. The elements B, Al, Ga, In and Tl are placed in the same group of the periodic table because each one has the same number of electrons (ns2 np1) in its valance shell.
3.Aluminium forms in not formed why?
Ans. Due to presence of vacant d-orbital’s, Al can expand its octet to form bonds with six fluoride ions whereas B cannot. Boron does not have d-orbital’s.
4.The atomic radius of Ca is less than that of Al. Why?
Ans. This is due to the variation in the inner core of the electronic configuration. The presence of additional 10 d-electrons offer only poor screening effect for the outer electrons from the increased nuclear charge in gallium.
5.C and S are always tetravalent but Ge, Sn And Pb show divalency. Why?
Ans. Inert pair is more prominent as we move down the group in p – block elements. Ge, Sn and Pb show divalency due to inert pair effect.
6.Some halides of group 14 elements form complexes of the type . Give reason.
Ans. The halides of the elements having vacant d-orbital’s can form complexes like 
7.is lead known whereas not. Give reason.
Ans. The main reasons are that
(i) Six large chloride ions cannot be accommodated around Si4+ due to limitation of its size.
(ii) Interaction between lone pair of chloride ion and Si4+ is not very strong.
8.PbI4 does not exist. Why?
Ans.PbI4 does not exist because Pb – I bond initially formed during the reaction does not release enough energy to unpair 6s2 electrons and excite one of them to higher orbital to have four unpaired electrons around lead atom.
9.Why is carbon different from other member of the group?
Ans. Carbon differs from rest of the members of its group due to its smaller size, higher electro negativity, higher ionization enthalpy and unavailability of d-orbital’s.
10.Why does the covalence of carbon not expand beyond four?
Ans. In carbon, only s and p orbital’s are available for bonding and therefore it can accommodate only four pairs of electrons around it. This limit the maximum covalence to four whereas other members can expand their covalence due to the presence of d-orbital’s.
11.Why does carbon show different allotropic forms?
Ans. Due to property of catenation and pπ – pπ bond formation Carbon is able to show different allotropic forms.
12.Silicon has no allotropic form analogous to graphite. Why?
Ans. Due to large size. Si has little or no tendency for pπ – pπ bonding. Whereas carbon atom forms easily pπ – pπ bonds due to smaller size in graphite structure. Hence, Si does not exhibit graphite structure.
13.Why does graphite conduct electricity?
Ans. Graphite forms hexagonal ring and undergoes sp2 hybridization. The electrons are delocalized over the whole sheet. Electrons are mobile and therefore graphite conducts electricity over the sheet.
14.Graphite is used as lubricant. Give reason.
Ans. Graphite has sp2 hybridized carbon with a layer structure due to wide separation and weak inter – layer bonds the two adjacent layers can easily slide over each other. This makes graphite act as a lubricant.
15.How are silicones manufactured?
Ans.They are manufactured by hydrolysis of chlorosilanes –
where R is a methyl or phenyl group.
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