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Here we have some questions based on Classification of Elements and Periodicity in Properties Class 11 Questions with MCQs and Short answer Type of 1 mark each.
Q-1. Consider the following isoelectronic species, Na+, Mg2+, F–and O2–. The correct order of increasing the length of their given radii is _________.
(i) F– < O2- < Mg2+ < Na+
(ii) Mg2+ < Na+< F–< O2-
(iii) O2-< F– < Na+< Mg2+
(iv) O2- < F– < Mg2+ < Na+
Ans: ii
Q-2. Which among the following is not an actinoid?
(i) Curium (Z = 96)
(ii) Californium (Z = 98)
(iii) (Z = 92)
(iv) Terbium (Z = 65)
Ans: iv
Q-3. The order of screening effect of the electrons of s, p, d and f orbitals for the given shell of an atom on their outer shell electrons will:
(i) s > p > d > f
(ii) f > p > s > d
(iii) p < d < s > f
(iv) f > d > p > s
Ans-i
Q-4. The first ionisation enthalpies of the Na, Mg, Al and Si are in the order as follows:
(i) Na < Mg > Al < Si
(ii) Na > Mg > Al > Si
(iii) Na < Mg < Al < Si
(iv) Na > Mg > Al < Si
Ans-(i)
Q-5. The electronic configuration of the given gadolinium (Atomic number 64) is
(i) [Xe] 4f3 5d5 6s2
(ii) [Xe] 4f7 5d2 6s1
(iii) [Xe] 4f7 5d1 6s2
(iv) [Xe] 4f8 5d6 6s2
Ans-(iii)
Q-6. The statement which is not correct for the following periodic classification of elements is:
(i) The properties of elements are periodic functions of their given atomic numbers.
(ii) The Non-metallic elements are less in number than the metallic elements.
(iii) For the given transition elements, the 3d-orbitals fill with the electrons after the 3p-orbitals and before the 4s-orbitals.
(iv) The first ionisation enthalpies of the given elements generally increase with an increase in the atomic number as we go along the period.
Ans:iii
Q-7. Among halogens, correct order of the amount of the energy released in the given electron gain (electron gain enthalpy) will:
(i) F < Cl < Br < I
(iv) F > Cl > Br > I
(iii) F < Cl > Br > I
(ii) F < Cl < Br < I
Ans: iii
Q-8. The period number at the long form of the given periodic table is equal to
(i) the magnetic quantum number of any given element of the period.
(ii) an atomic number of any given element of the period.
(iii) maximum Principal quantum number of any given period element.
(iv) maximum Azimuthal quantum number of any given period element.
Ans: iii
Q-9. The elements in which the given electrons progressively fill in the 4f-orbitals call
(i) actinoids
(ii) transition elements
(iii) lanthanoids
(iv) halogens
Ans-iii
Q-10. Which among the following is the correct order of the size of the given species:
(i) I > I– > I+
(ii) I+> I– > I
(iii) I > I+ > I-
(iv) I– > I > I+
Ans: (iv)
Q-11. The formation of the given oxide ion, O2– (g), from the oxygen atom, requires first an exothermic and then an endothermic step as stated below:
O (g) + e– à O–(g) ;∆ HV = – 141 kJ mol–1
O– (g) + e– à O2– (g) ; ∆ HV = + 780 kJ mol–1
Thus, the formation process of O2– in the given gas phase is unfavourable even though O2– is isoelectronic with the neon. It is because of this fact that
(i) oxygen is more electronegative.
(ii) addition of the electrons in oxygen results in the larger size of the ion.
(iii) electron repulsion outweighs stability gained by achieving the noble gas configuration.
(iv) O– ion is smaller than a given oxygen atom.
Ans:(iii)
Q-12. Electronic configurations of the following four elements, A, B, C and D, have given below:
(A) 1s2 2s2 2p6
(B) 1s2 2s2 2p4
(C) 1s2 2s2 2p6 3s1
(D) 1s2 2s2 2p5
Which among the following is the correct order of increasing the tendency to gain the electrons :
(i) A < C < B < D
(ii) D < A < B < C
(iii) D < B < C < A
(iv) A < B < C < D
AnS:12:(i)
Q-13. Which among the following elements can show the covalency more than the 4?
(i) B
(ii) P
(iii) Li
(iv) Be
Ans: (ii)
Don’t Forget to click Class 11 Atomic structure MCQs & Assertion Reasoning Questions
Q-14. Those elements which impart colour to the flame on heating in it are the atoms that require low energy for the ionisation (i.e., absorb energy in the visible region of the spectrum). The elements of which among the following groups will impart colour to the flame?
(i) 2
(ii) 13
(iii) 16
(iv) 17
Ans: (i)
Q-15. Which among the following sequences contains atomic numbers of only representative elements?
(i) 3, 33, 53, 87
(ii) 2, 10, 22, 36
(iii) 7, 17, 25, 37, 48
(iv) 9, 36, 52, 88
Ans:(i)
Classification of Elements and Periodicity in Properties Class 11 Questions: Short Answer Type
Very Short Answer Type Question:
Q-17. Explain why the electron gain enthalpy of the elemental fluorine is less negative than the elemental chlorine.
Ans: Fluorine has a smaller size as compared to chlorine. As a result, the attraction outside the shell to gain the electrons is less. Moreover, they possess inter-electronic repulsions in the 2p orbitals, resulting in less negative electron gain enthalpy.
Q-18. All the transition elements are d-block elements, but all the d-block elements are not the transition elements. Explain.
Ans:The elements having their outermost shell filled with the d electrons are called the d block elements. All the d blocks are not the transition elements as it is important to have an incompletely filled d orbital of the given element like calcium and zinc etc.
Q-19. Identify the group and valency of the following element having atomic number 119. Also, predict the outermost electronic configuration for it and write the general formula of the oxide.
Ans: There are 118 elements found in the seven periods of the modern periodic table. Thus, the element with the atomic number 119 will lie in the 8th period of the first group and have the outermost electronic configuration of 8s1. It belongs to group 1 and has the valency one. The formula of the oxide would be M2O.
Q- 20. Ionisation enthalpies of a few elements of the second period are given below: Ionisation enthalpy/ kcal mol–1: 520, 899, 801, 1086, 1402, 1314, 1681, 2080.
Here, Match the correct enthalpy by the given elements and complete the graph in the Fig. Also, write symbols of the elements with the given atomic number.
Ans: The ionisation enthalpy of the given elements varies across the period and group. The ionisation enthalpy decreases down the group and increases as we move from left to right in the period.
Q-21. Among the given elements B, Al, C and Si,
(i) which of the following elements has the highest first ionisation enthalpy?
(ii) which element contains the most metallic character? Explain your answer in each case.
Ans: (i) Carbon possesses the highest ionisation enthalpy. It increases from left to right along the period and also decreases as we go down the group.
(ii) Aluminium possesses the most metallic character. On moving down, the metallic character increases and decreases across the period from left to right.
Q-22. Write the four characteristic properties for the p-block elements.
Ans: 1. They show the variable oxidation states. The trend of the reducing character increases on moving down the group, and oxidising character increases as we move along the period.
- They have a higher ionisation enthalpy than the s-block elements.
- They usually form the given covalent compounds.
- Both metals and non-metals can be found in this group, but the non-metals are slightly more in number.
Q-23. Nitrogen possesses the positive electron gain enthalpy, whereas the oxygen possesses the negative. But oxygen has lower ionisation enthalpy than nitrogen. Explain.
Ans: The ionisation enthalpy of oxygen is lower than that of nitrogen as when we remove one electron from the oxygen then it easily donates it to attain half-filled stability; however, in the case of nitrogen, it is difficult to remove one electron because it already has half-filled stability and it will become unstable after that.
Q-24. The first member of each group of the representative elements, s and p-block elements, shows abnormal behaviour. Illustrate with the help of two examples.
Ans- Lithium and beryllium are the examples. Li is the first group element. It has different properties as well as forms the covalent compounds as well as nitrides. Beryllium is the first element of the second group. It has various anomalies like it forms the covalent compound with coordination number four, unlike other elements with the coordination number 6.
Q-25. How will you explain that the first ionisation enthalpy of sodium is quite lower than that of magnesium; however, its second ionization enthalpy is quite higher than that of magnesium?
Ans: Sodium attains the stable configuration if it loses on an electron from the outermost shell. That is why its first ionisation enthalpy is less than the magnesium. However, in the case of the second ionisation, magnesium has one electron in its outermost shell to attain stability; it loses the electron easily compared to sodium, which is already stable.
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Q-26. The radius of the Na+ cation is less than that of the Na atom. Give reasons for your answer.
Ans: Sodium atoms can lose one electron to form sodium cation. After the formation of the cation, the effective nuclear charge on the ion increases on the left electrons, resulting in the decrease of the radius.
Q-27. Among alkali metals which element can be least electronegative and why?
Ans-Ceasium is the least electronegative alkali metal because electronegativity decreases as we move from top to bottom due to increase in size.. Caesium is the group 1 element and lies down the group because it has the largest size due to the decrease in the effective nuclear charge.
Q-28. Arrange the following elements N, P, O and S in the order of-
(i) increasing first ionisation enthalpy.
(ii) increasing non-metallic character.
Justify your answer with reason
Ans:
(i) S< P< O< N is the accurate, increasing order of the first ionisation enthalpy.
On going down the group, the ionisation enthalpy decreases, and as we move along the period, then it increases; however, in the case of oxygen and nitrogen, because of the half-filled stability of 2p orbitals of nitrogen, it has the higher ionisation enthalpy than oxygen.
(ii) P<S<N<O is the accurate, increasing order of non-metallic character.
Moving down the group, we will see non-metallic character decrease as the effective nuclear charge on the outermost shell decreases, which helps to gain an electron. The effective nuclear charge increases moving along the period, increasing the non-metallic character.