Class 11 Chemistry · 47 questions · 39 with answers
Consider the isoelectronic species, Na+, Mg , F and O . The correct order of increasing length of their radii is _________. 2– 2+ +
(ii) Mg < Na < F < O 2– – + 2+
Which of the following is not an actinoid?
(iv) Terbium (Z = 65)
The order of screening effect of electrons of s, p, d and f orbitals of a given shell of an atom on its outer shell electrons is:
(i) s>p>d>f
The first ionisation enthalpies of Na, Mg, Al and Si are in the order:
(i) Na < Mg > Al < Si
The electronic configuration of gadolinium (Atomic number 64) is 3 5 2 (i) [Xe] 4f 5d 6s
2 1 (ii) [Xe] 4f 5d 6s 7 1 2 (iii) [Xe] 4f 5d 6s
6 2 (iv) [Xe] 4f 5d 6s 6. 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. 7. 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 8. 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 elements in which electrons are progressively filled in 4f-orbital are called
(iii) lanthanoids
Which of the following is the correct order of size of the given species: – +
(iv) I >I>I
The formation of the oxide ion, O2– (g), from oxygen atom requires first an exothermic and then an endothermic step as shown below: V –1 O (g) + e– → O– (g) ; ∆ H = – 141 kJ mol V –1 O – (g) + e– → O2– (g); ∆ H = + 780 kJ mol 2– Thus process of formation of O in gas phase is unfavourable even though 2– O is isoelectronic with neon. It is due to the fact that,
(iii) electron repulsion outweighs the stability gained by achieving noble gas configuration. –
(i) oxygen is more electronegative.
(ii) addition of electron in oxygen results in larger size of the ion.
(iv) O ion has comparatively smaller size than oxygen atom.
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
Electronic configurations of four elements A, B, C and D are given below : (A) 1s2 2s2 2p6 (B) 1s2 2s 2 2p 4 (C) 1s2 2s2 2p6 3s1 (D) 1s2 2s 2 2p 5 Which of the following is the correct order of increasing tendency to gain electron :
(i) A<C<B<D
Which of the following elements can show covalency greater than 4?
(ii) P
(iii) S
Those elements impart colour to the flame on heating in it, the atoms of which require low energy for the ionisation (i.e., absorb energy in the visible region of spectrum). The elements of which of the following groups will impart colour to the flame?
(i) 2
(iii) 1
Which of the following sequences contain atomic numbers of only representative elements?
(i) 3, 33, 53, 87
(iv) 9, 35, 51, 88
Which of the following elements will gain one electron more readily in comparison to other elements of their group?
(i) S (g)
(iv) Cl (g)
Which of the following statements are correct?
(i) Helium has the highest first ionisation enthalpy in the periodic table.
(iii) Mercury and bromine are liquids at room temperature.
(iv) In any period, atomic radius of alkali metal is the highest.
Which of the following sets contain only isoelectronic ions? 2+ 2+ 3+ 3+
(ii) K , Ca , Sc , Cl 3– 2– – +
(iii) P , S , Cl , K 4+ 3+ 5+
In which of the following options order of arrangement does not agree with the variation of property indicated against it? 3+ 2+ + –
(ii) B < C < N < O (increasing first ionisation enthalpy)
(iii) I < Br < Cl < F (increasing electron gain enthalpy)
Which of the following have no unit?
(i) Electronegativity
(iv) Metallic character 31 Classification of Elements and Periodicity in Properties
Ionic radii vary in
(i) inverse proportion to the effective nuclear charge.
(iii) direct proportion to the screening effect.
An element belongs to 3rd period and group-13 of the periodic table. Which of the following properties will be shown by the element?
(i) Good conductor of electricity
(iii) Solid, metallic
Explain why the electron gain enthalpy of fluorine is less negative than that of chlorine.
The added electron in fluorine goes to second quantum level. Due to small size of fluorine it experiences repulsion from other electrons much more in comparison to that in chlorine because in chlorine, the electron is added to 3rd quantum level in which larger space is available for movement.
All transition elements are d-block elements, but all d-block elements are not transition elements. Explain.
Identify the group and valency of the element having atomic number 119. Also predict the outermost electronic configuration and write the general formula of its oxide.
Group : 1, Valency : 1 Outermost electronic configuration = 8s1 Formula of Oxide = M2O
Ionisation enthalpies of elements of second period are given below : Ionisation enthalpy/ k cal mol–1 : 520, 899, 801, 1086, 1402, 1314, 1681, 2080. Match the correct enthalpy with the elements and complete the graph given in Fig. 3.1. Also write symbols of elements with their atomic number.
This question refers to a figure in the original PDF.
Compare your plot with the plot given in the textbook.
Among the elements B, Al, C and Si,
This question refers to a figure in the original PDF.
(i) which element has the highest first ionisation enthalpy?
(ii) which element has the most metallic character? Justify your answer in each case. Fig. 3.1
Write four characteristic properties of p-block elements.
Choose the correct order of atomic radii of fluorine and neon (in pm) out of the options given below and justify your answer.
(i) 72, 160
Illustrate by taking examples of transition elements and non-transition elements that oxidation states of elements are largely based on electronic configuration.
Nitrogen has positive electron gain enthalpy whereas oxygen has negative. However, oxygen has lower ionisation enthalpy than nitrogen. Explain.
The outermost electronic configuraton of nitrogen (2s2 2px1 2py1 2pz1) is very stable because p-orbital is half filled. Addition of extra electron to any of the 2p orbital requires energy. Oxygen has 4 electrons in 2p orbitals and acquires stable configuration i.e., 2p3 configuration after removing one electron.
First member of each group of representative elements (i.e., s and p-block elements) shows anomalous behaviour. Illustrate with two examples.
p-Block elements form acidic, basic and amphoteric oxides. Explain each property by giving two examples and also write the reactions of these oxides with water.
How would you explain the fact that first ionisation enthalpy of sodium is lower than that of magnesium but its second ionisation enthalpy is higher than that of magnesium?
After removing 1 electron from the sodium atom the ion formed acquires the configuration of inert gas, neon. The second electron is removed from one of the 2p-orbitals which are completely filled i.e., have a total of 6 electrons and are closer to the nucleus. 37 Classification of Elements and Periodicity in Properties
What do you understand by exothermic reaction and endothermic reaction? Give one example of each type.
Arrange the elements N, P, O and S in the order of-
(i) increasing first ionisation enthalpy.
(ii) increasing non metallic character. Give reason for the arrangement assigned.
Explain the deviation in ionisation enthalpy of some elements from the general trend by using Fig. 3.2. Fig. 3.2 33 Classification of Elements and Periodicity in Properties
This question refers to a figure in the original PDF.
Explain the following:
(a) Electronegativity of elements increase on moving from left to right in the periodic table.
(b) Ionisation enthalpy decrease in a group from top to bottom?
How does the metallic and non metallic character vary on moving from left to right in a period?
Metallic character decreases and non metallic character increases in moving from left to right in a period. It is due to increase in ionisation enthalpy and electron gain enthalpy.
The radius of Na+ cation is less than that of Na atom. Give reason.
Decrease of one shell.
Among alkali metals which element do you expect to be least electronegative and why?
Electronegativity decreases in a group from top to bottom. Thus, caesium is the least electronegative element. IV. Matching Type
Match the correct atomic radius with the element. Element Atomic radius (pm) Be 74 C 88 O 111 B 77 N 66
Be = 111, O = 66, C = 77, B = 88, N = 74.
Match the correct ionisation enthalpies and electron gain enthalpies of the following elements. Elements ∆ H1 ∆ H2 ∆ eg H
(ii) Most reactive metal B. 1681 3374 – 328
(i) Most reactive non metal A. 419 3051 – 48
(iv) Metal forming binary halide D. 2372 5251 + 48
(iii) Least reactive element C. 738 1451 – 40
Electronic configuration of some elements is given in Column I and their electron gain enthalpies are given in Column II. Match the electronic configuration with electron gain enthalpy. Column (I) Column (II) Electronic configuration Electron gain enthalpy/kJ mol–1 (i) 1s2 2s2 sp6
(A) – 53 (ii) 1s2 2s2 2p6 3s1
(D) + 48
(B) – 328 (iii) 1s2 2s2 2p5
(C) – 141 (iv) 1s2 2s2 2p4
Assertion (A): Generally, ionisation enthalpy increases from left to right in a period.
Reason (R): When successive electrons are added to the orbitals in the same principal quantum level, the shielding effect of inner core of electrons does not increase very much to compensate for the increased attraction of the electron to the nucleus.
Assertion (A): Boron has a smaller first ionisation enthalpy than beryllium.
Reason (R): The penetration of a 2s electron to the nucleus is more than the 2p electron hence 2p electron is more shielded by the inner core of electrons than the 2s electrons.
Assertion (A): Electron gain enthalpy becomes less negative as we go down a group.
Reason (R): Size of the atom increases on going down the group and the added electron would be farther from the nucleus.