chemistry - classification of elements and periodicity in properties

Class 11 - Chemistry

Classification of Elements and Periodicity in Properties

MCQ
Q&A
Question:

Considering the elements F, Cl, O and N, the correct order of their chemical reactivity in terms of oxidising property is:
(a) F > Cl> O > N (b) F > O > Cl> N (c) Cl> F > O > N (d) O > F > N > Cl

Answer:

Within a period, the oxidising character increases from left to right. Therefore, among F, O and N, oxidising power decreases in the order: F > O > N. However, within a group, oxidising power decreases from top to bottom. Thus, F is a stronger oxidising agent than Cl. Further because O is more electronegative than Cl, therefore, O is a stronger oxidising agent than Cl. Thus, overall decreasing order of oxidising power is: F > O > Cl > N, i.e., option (b) is correct.



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Questions and Answers


Classification of Elements and Periodicity in Properties - Questions
1.

Would you expect the first ionization enthalpies of two isotopes of the same element to be the same or different? Justify your answer.


Answer
2.

What are major differences between metals and non-metals?


Answer
3.

Use periodic table to answer the following questions:
(a) Identify the element with five electrons in the outer subshell.
(b) Identify the element that would tend to lose two electrons.
(c) Identify the element that would tend to gain two electrons.


Answer
4.

Write the general electronic configuration of spd, and f-block elements?


Answer
5.

Assign the position of the element having outer electronic configuration,
(i) ns2 np4  for n = 3 (ii) (n – 1) d2 ns2 for n = 4 and (iii) (n – 2) f7 (n – 1) d1 ns2  for n = 6 in the periodic table?


Answer
6.

Predict the formulas of the stable binary compounds that would be formed by the combination  of the following pairs of elements:
(a) Lithium and oxygen(b) Magnesium and nitrogen
(c) Aluminium and iodine(d) Silicon and oxygen
(e) Phosphorous pentafluoride (f) Element 71 and fluorine.


Answer
7.

In the modem periodic table, the period indicates the value of
(a)atomic number (b) mass number (c) principal quantum number (d) azimuthal quantum number?


Answer
8.

Considering the elements B, Al, Mg and K, the correct order of their metallic character is:(a) B> Al> Mg > K(b) Al> Mg > B> K (c) Mg > Al> K> B (d) K> Mg > Al> B


Answer
9.

State the Modem Periodic Law.


Answer
10.

Why is ionization enthalpy of nitrogen greater than that of oxygen?


Answer
11.

Why are electron gain enthalpies of Be and Mg positive?


Answer
12.

Give four examples of species which are isoelectronic with  ca2+.


Answer
13.

Which two elements of the following belong to the same period?
Al, Si, Ba and O


Answer
14.

What are horizontal rows and vertical columns of the periodic table called?


Answer
15.

Which has a larger radius?
(i)Mg or Ca (ii) S or Cl


Answer
16.

The electronic configuration of an element is Is 2s 2p 3s 3p 4s . Locate the element in the periodic table.


Answer
17.

What is the cause of periodicity in properties of the elements? Explain with two examples.


Answer
18.

Define the term ionization enthalpy? How does it vary along a period and along a group?


Answer
19.

Discuss briefly the various factors on which ionization enthalpy depends.


Answer
20.

What are Dobereiner’s triads? Name two such triads.


Answer
21.

Give the electronic configuration of the transition elements. Write their four important characteristics.


Answer
22.

What is screening or shielding effect? How does it influence the ionization enthalpy ?


Answer
23.

Discuss the main features of long form of the periodic table. What are the advantages of long . form of periodic table?


Answer
24.

Discuss the factors that influence the magnitude of ionization enthalpy. What are the general trends of variation of ionization enthalpy in the periodic table? Explain.


Answer
25.

(a) How does atomic radius vary in group in the periodic table?
(b) Explain
(i) Radius of cation is less than that of the atom.
(ii) Radius of anion is more than that of the atom.
(iii) In iso-electronic ion, the ionic radii decreases with increase in atomic number.


Answer
26.

Arrange the following as stated: (i) N2, 02, F2, Cl2(Increasing order of bond dissociation energy) (ii) F, Cl, Br, I (Increasing order of electron gain enthalpy) (iii)  F2, N2, Cl2, O2(Increasing order of bond length).


Answer
27.

The first ionisation enthalpy of magnesium is higher than that of sodium. On the other hand, the second ionisation enthalpy of sodium is very much higher than that of magnesium. Explain.


Answer
28.

Give reasons:
(i) IE1  of sodium is lower than that of magnesium whereas  IE2  of sodium is higher than that of magnesium.
(ii) Noble gases have positive value of electron gain enthalpy.


Answer
29.

Consider the isoelectronic species, Na+, Mg2+, F and O2-. The correct order  of increasing length of their radii is

ncert-exemplar-problems-class-11-chemistry-chapter-3-classification-of-elements-and-periodicity-in-properties-1


Answer
30.

The first ionization enthalpies of Na, Mg, A1 and Si are in the order
(a)       Na < Mg > A1 < Si                                                    
(b)         Na>Mg>Al>Si
(c)       Na < Mg < A1 < Si                                                    
(d)       Na > Mg > A1 < Si


Answer
31.

The electronic configuration of gadolinium (Atomic number 64) is

ncert-exemplar-problems-class-11-chemistry-chapter-3-classification-of-elements-and-periodicity-in-properties-2


Answer
32.

The formation of the oxide ion, 02-(g), from oxygen atom requires first an exothermic and then an endothermic step as shown below:
O(g) + e→0 (g), ∆H= -141 kJ mol-1
0(g) + e→O2 (g), ∆H = +780 kJ mol-1
Thus process of formation of O2- ion in gas phase is unfavourable even though O2- is isoelectronic with neon. It is due to the fact that

(a) Oxygen is more electronegative.
(b) Addition of electron in oxygen results in larger size of the ion.
(c) Electron repulsion outweighs the stability gained by achieving noble gas configuration.
(d) 0 ion has comparatively smaller size than oxygen atom.


Answer
33.

Electronic configurations of four elements A, B, C and D are given below:
(A) 1s2 2s12p6                          
(B)  1 s2 2s2 2p4
(C)     1s2 2s2 2p6 3s1                                                                    
(D)       Is2 2s2 2p5

Which of the following is the correct order of increasing tendency to gain electron?

(a) A < C < B < D
(b)         A < B < C < D
(c)       D < B < C < A                                                                  
(d)         D < A< B < C


Answer
34.

Which of the following elements can show covalency greater than 4?
(a) Be (b) P (c) S (d) B


Answer
35.

Those elements impart colour to the flame on heating in it, the atoms of which require low energy for the ionization (i.e., absorb energy in the visible region of spectrum). The elements of which of the following groups will impart colour to the flame?
(a) 2 (b) 13 (c) 1 (d) 17


Answer
36.

Which of the following sequences contain atomic numbers of only representative elements?
(a) 3, 33, 53, 87
(b) 2, 10, 22, 36
(c) 7, 17,25,37,48
(d) 9,35,51,88


Answer
37.

Which of the following elements will gain one electron more readily in comparison to other elements of their group?
(a) S (g) (b) Na (g) (c) O (g) (d) Cl(g)


Answer
38.

Which of the following statements are correct?
(a) Helium has the highest first ionization enthalpy in the periodic table.
(b) Chlorine has less negative electron gain enthalpy than fluorine.
(c) Mercury and bromine are liquids at room temperature.
(d) In any period, atomic radius of alkali metal is the highest.


Answer
39.

Which of the following sets contain only isoelectronic ions?
(a) Zn2+, Ca2+, Ga3+, Al3+                                              
(b) K+, Ca2+, Sc3+, Cl
(c) P3-, S2- Cl,K+                                                    
(d) Ti4+, Ar, Cl3+, V5+


Answer
40.

In which of the following options order of arrangement does not agree with the variation of property indicated against it?
(a) Al3+ < Mg2+ < Na+ < F (increasing ionic size)
(b) B < C < N < O (increasing first ionization enthalpy)
(c) I < Br < Cl < F (increasing electron gain enthalpy)
(d) Li < Na < K < Rb (increasing metallic radius)


Answer
41.

Which of the following have no unit?
(a) Electronegativity (b) Electron gain enthalpy
(c) Ionisation enthalpy (d) Metallic character


Answer
42.

An element belongs to 3rd period and group-13 of the periodic table. Which of the following properties will be shown by the element?
(a) Good conductor of electricity
(b) Liquid, metallic
(c) Solid, metallic    
(d) Solid, non metallic


Answer
43.

Explain why the electron gain enthalpy of fluorine is less negative than that of chlorine.


Answer
44.

All transition elements are d-block elements, but all d-block elements are not transition elements. Explain.


Answer
45.

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.


Answer
46.

Ionisation enthalpies of elements of second period are given below:
Ionisation enthalpy/kJ mol-1: 520, 899, 801, 1086, 1402, 1314, 1681, 2080. Match the correct enthalpy with the elements and complete the graph given in figure. Also write symbols of elements with their atomic number.
ncert-exemplar-problems-class-11-chemistry-chapter-3-classification-of-elements-and-periodicity-in-properties-5


Answer
47.

Among the elements B, Al, C and Si,
(a) which element has the highest first ionization enthalpy
(b) which element has the most metallic character?
Justify your answer in each case.


Answer
48.

Write four characteristic properties of p-block elements.


Answer
49.

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 (b) 160,160 (c) 72,72 (d) 160,72


Answer
50.

Illustrate by taking examples of transition elements and non-transition elements that oxidation states of elements are largely based on electronic configuration.


Answer
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