Ncert Solutions Chemistry Class 11th
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Comprehension given below is followed by some multiple choice questions. Each question has one correct option. Choose the correct option.
In the modern periodic table, elements are arranged in order of increasing atomic numbers which is related to the electronic configuration. Depending upon the type of orbitals receiving the last electron, the elements in the periodic table have been divided into four blocks, viz, s, p, d and f. The modern periodic table consists of 7 periods and 18 groups. Each period begins with the filling of a new energy shell. In accordance with the Arfbau principle, the seven periods (1 to 7) have 2, 8, 8, 18, 18, 32 and 32 elements respectively. The seventh period is still incomplete. To avoid the periodic table being too long, the two series of f-block elements, called lanthanoids and actinoids are placed at the bottom of the main body of the periodic table.
(a) The element with atomic number 57 belongs to
(i) s-block
(ii) p-block
(iii) d-block
(iv) f-block
Comprehension given below is followed by some multiple choice questions. Each question has one correct option. Choose the correct option.
In the modern periodic table, elements are arranged in order of increasing atomic numbers which is related to the electronic configuration. Depending upon the type of orbitals receiving the last electron, the elements in the periodic table have been divided into four blocks, viz, s, p, d and f. The modern periodic table consists of 7 periods and 18 groups. Each period begins with the filling of a new energy shell. In accordance with the Arfbau principle, the seven periods (1 to 7) have 2, 8, 8, 18, 18, 32 and 32 elements respectively. The seventh period is still incomplete. To avoid the periodic table being too long, the two series of f-block elements, called lanthanoids and actinoids are placed at the bottom of the main body of the periodic table.
(a) The element with atomic number 57 belongs to
(i) s-block
(ii) p-block
(iii) d-block
(iv) f-block
This is a Multiple Choice Questions as classified in NCERT Exemplar
Option (iii) d-block
Lanthanum is the element with the atomic number 57 and it belongs to the d-block.
Upvote 
The formation of the oxide ion, O2– (g), from oxygen atom requires first an exothermic and then an endothermic step as shown below:
O(g) + e– → O– (g) ; ∆ Hᶱ = – 141 kJ mol–1
O– (g) + e– → O2– (g); ∆ Hᶱ = + 780 kJ mol–1
Thus process of formation of O2– in gas phase is unfavourable even though O2– is isoelectronic with neon. It is due to the fact that,
(i) Oxygen is more electronegative.
(ii) Addition of electron in oxygen results in larger size of the ion.
(iii) Electron repulsion outweighs the stability gained by achieving noble gas configuration.
(iv) O– ion has comparatively smaller size than oxygen atom.
The formation of the oxide ion, O2– (g), from oxygen atom requires first an exothermic and then an endothermic step as shown below:
O(g) + e– → O– (g) ; ∆ Hᶱ = – 141 kJ mol–1
O– (g) + e– → O2– (g); ∆ Hᶱ = + 780 kJ mol–1
Thus process of formation of O2– in gas phase is unfavourable even though O2– is isoelectronic with neon. It is due to the fact that,
(i) Oxygen is more electronegative.
(ii) Addition of electron in oxygen results in larger size of the ion.
(iii) Electron repulsion outweighs the stability gained by achieving noble gas configuration.
(iv) O– ion has comparatively smaller size than oxygen atom.
This is a Multiple Choice Questions as classified in NCERT Exemplar
Option (iii)
High amount of energy has to be supplied in order to overcome the e- - e - repulsion that arises when O- gets converted to O2- by accepting an electron
Upvote Which of the following is the correct order of size of the given species:
(i) I > I – > I +
(ii) I + > I – > I
(iii) I > I + > I –
(iv) I – > I > I+
Which of the following is the correct order of size of the given species:
(i) I > I – > I +
(ii) I + > I – > I
(iii) I > I + > I –
(iv) I – > I > I+
This is a Multiple Choice Questions as classified in NCERT Exemplar
Option (iv)
I+ possess the highest effective nuclear charge whereas I- possess the least among the given species.
Upvote The elements in which electrons are progressively filled in 4f-orbital are called
(i) Actinoids
(ii) Transition elements
(iii) Lanthanoids
(iv) Halogens
The elements in which electrons are progressively filled in 4f-orbital are called
(i) Actinoids
(ii) Transition elements
(iii) Lanthanoids
(iv) Halogens
This is a Multiple Choice Questions as classified in NCERT Exemplar
Option (iii)
The lanthanoids which belong to the f-block elements are the elements where 4forbitals are filled progressively.
Upvote The period number in the long form of the periodic table is equal to
(i) Magnetic quantum number of any element of the period.
(ii) Atomic number of any element of the period.
(iii) Maximum Principal quantum number of any element of the period.
(iv) Maximum Azimuthal quantum number of any element of the period.
The period number in the long form of the periodic table is equal to
(i) Magnetic quantum number of any element of the period.
(ii) Atomic number of any element of the period.
(iii) Maximum Principal quantum number of any element of the period.
(iv) Maximum Azimuthal quantum number of any element of the period.
This is a Multiple Choice Questions as classified in NCERT Exemplar
Option (iii)
Period number indicates the maximum value of principal quantum number
Upvote Among halogens, the correct order of amount of energy released in electron gain (electron gain enthalpy) is:
(i) F > Cl > Br > I
(ii) F < Cl < Br < I
(iii) F < Cl > Br > I
(iv) F < Cl < Br < I
Among halogens, the correct order of amount of energy released in electron gain (electron gain enthalpy) is:
(i) F > Cl > Br > I
(ii) F < Cl < Br < I
(iii) F < Cl > Br > I
(iv) F < Cl < Br < I
This is a Multiple Choice Questions as classified in NCERT Exemplar
Option (i)
The electron gain enthalpy decreases down the group, however as the size of F atom is much smaller thus it leads to repulsion upon addition of electrons on its 2p orbital for this electron gain enthalpy of Cl is higher than
Upvote The statement that is not correct for periodic classification of elements is:
(i) The properties of elements are periodic function of their atomic numbers.
(ii) Non metallic elements are less in number than metallic elements.
(iii) For transition elements, the 3d-orbitals are filled with electrons after 3p-orbitals and before 4s-orbitals.
(iv) The first ionisation enthalpies of elements generally increase with increase in atomic number as we go along a period.
The statement that is not correct for periodic classification of elements is:
(i) The properties of elements are periodic function of their atomic numbers.
(ii) Non metallic elements are less in number than metallic elements.
(iii) For transition elements, the 3d-orbitals are filled with electrons after 3p-orbitals and before 4s-orbitals.
(iv) The first ionisation enthalpies of elements generally increase with increase in atomic number as we go along a period.
This is a Multiple Choice Questions as classified in NCERT Exemplar
Option (iii)
As per Aufbau principle 3d orbitals are filled first than 4s as due to lower n value.
Upvote The electronic configuration of gadolinium (Atomic number 64) is
(i) [Xe] 4f 3 5d5 6s2
(ii) [Xe] 4f7 5d2 6s1
(iii) [Xe] 4f7 5d1 6s2
(iv) [Xe] 4f8 5d6 6s2
The electronic configuration of gadolinium (Atomic number 64) is
(i) [Xe] 4f 3 5d5 6s2
(ii) [Xe] 4f7 5d2 6s1
(iii) [Xe] 4f7 5d1 6s2
(iv) [Xe] 4f8 5d6 6s2
This is a Multiple Choice Questions as classified in NCERT Exemplar
Option (iii)
Gadolinium is a lanthanoid which belongs to the f-block elements with electronic configuration (n-2)f14 (n-1)d0-1ns2
Upvote The first ionisation enthalpies of Na, Mg, Al and Si are in the order:
(i) Na < Mg > Al < Si
(ii) Na > Mg > Al > Si
(iii) Na < Mg < Al < Si
(iv) Na > Mg > Al < Si
The first ionisation enthalpies of Na, Mg, Al and Si are in the order:
(i) Na < Mg > Al < Si
(ii) Na > Mg > Al > Si
(iii) Na < Mg < Al < Si
(iv) Na > Mg > Al < Si
This is a Multiple Choice Questions as classified in NCERT Exemplar
Option (i)
As Mg contains fully filled 3s orbital thus its ionisation is higher than that of Na and Al.
Upvote