NCERT Exemplar Solution Class 10 Science Chapter 5
NCERT Exemplar Solution Class 10 Science Chapter 5 Periodic Classification of Elements all Questions Answer Solution. NCERT Exemplar Class 10 Science Chapter 5 Solution PDF.
NCERT Exemplar Solution Class 10 Science Chapter 5: Overview
NCERT Exemplar Solution Class 10 Science Chapter 5 |
|
Board |
NCERT |
Topic |
Exemplar Problem Solution |
Class |
10 |
Subject |
Science |
Chapter |
5 |
Chapter Name |
Periodic Classification of Elements |
NCERT Exemplar Solution Class 10 Science Chapter 5 Periodic Classification of Elements
Multiple Choice Questions
1) Upto which element, the law of octaves was found to be applicable
a) Oxygen
b) Calcium
c) Cobalt
d) Potassium
Answer:- b) calcium
Explanation: Upto Calcium which has Atomic mass 40 the Newlands octaves law is applicable, after that these law does bot obey the rule Of octaves.
2) According to Mendeleev’s periodic law, the elements were arranged in the periodic table in the order of
a) Increasing atomic number
b) Decreasing atomic number
c) Increasing atomic masses
d) Decreasing atomic masses
Answer:- c) increasing atomic number
Explanation: Mendeleev’s Modern Periodic Table is put forth on the basis of increasing atomic number of elements.
3) In Mendeleev’s periodic table, gaps were left for the elements to be discovered later. Which of the following elements found a place in the periodic table later
a) Germanium
b) Chlorine
c) Oxygen
d) Silicon
Answer:- a) Germanium
Explanation: All the elements were not discovered at that time thus Mendeleev put some gaps over there, and when it was discovered later the elements were placed in the respective gaps according to their atomic number.
4) Which of the following statements about the modern periodic table are incorrect
I) The elements in the modern periodic table are arranged on the basic of their decreasing atomic number.
II) The elements in the modern periodic table are arranged on the basic of their increasing atomic masses.
III) Isotopes are placed in adjoining group (s) in the periodic table
IV) The elements in the modern periodic table are arranged on the basic increasing Atomic number
a) I only
b) I, II, and III
c) I, II and IV
d) IV only
Answer:- d) IV only
Explanation: Modern periodic table is based on only one Principal that is increasing Atomic number of the elements. Other 3 options are wrong according to the periodic table.
5) Which of the following statements about the modern periodic table is correct:
a) It has 18 horizontal rows known as periods
b) It has 7 vertical column known as periods
c) It has 18 vertical columns known as groups
d) It has 7 horizontal rows known as Groups
Answer:- c) It has 18 vertical columns known as groups
Explanation: The modern periodic table consists of 18 vertical columns which are known as groups. And 7 horizontal rows which are known as periods.
6) Which of the given elements A,B,C,D and E with atomic number 2,3,7,10 and 30 respectively belongs to the same period ?
a) A,B,C
b) B,C,D
c) A,D,E
d) B,D,E
Answer:- b) B,C,D
Explanation: B, C, D which has Atomic number 3,7,10 respectivelybelongs to the same period i.e. period 2nd. Other remaining belongs to 1stperiod.
7) The elements A,B,C,D and E have Atomic number 9,11,17,12 and 13 respectively, which pair of elements belong to the same group ?
a) A and B
b) B and D
c) A and C
d) D and E
Answer:- c) A and C
Explanation: A and c which has Atomic number 9 and 17 respectively belongs to the same group. These elements are fluorine and Chlorine.
8) Where would you locate the element with electronic configuration 2,8 in the modern periodic table ?
a) Group 8
b) Group 2
c) Group 18
d) Group 10
Answer:- c) Group 18
Explanation: The element with electronic configuration 2,8 is Ne (Neon ) which belongs to the group 18.
9) An element which is an essential constituent of all organic compounds belongs to
a) Group 1
b) Group 14
c) Group 15
d) Group 16
Answer:- b) Group 14
Explanation: The essential constituent of all organic compounds is Carbon. Carbon belongs to group 14.
10) Which of the following is the outermost shell for elements of period 2 ?
a) K shell
b) L shell
c) M shell
d) N shell
Answer:- b) L shell
Explanation: Period 2 contains maximum 8 Electrons in its outermost shell hence it contains only 2 shell k and L. Thus outermost shell is L.
11) Which one of the following elements exhibit maximum numbers of valence electrons ?
a) Na
b) Al
c) Si
d) P
Answer:- d) P
Explanation: While the other elements have the atomic number of Na = 11, Al = 13, and Si = 14 while the p= 15. Thus the maximum number of valence electrons are present in phosphorous.
12) Which of the following gives the correct increasing order of the Atomic radii of O,F and N?
a) O,F,N
b) N,F,O
c) O,N,F
d) F,O,N
Answer:- d) F,O,N
Explanation: Fluorine, Oxygen and Nitrogen are present in the Increasing order in period. And atomic radii increases from left to right in a period. These is the right order.
13) Which among the following elements has the largest atomic radii?
a) Na
b) Mg
c) K
d) Ca
Answer:- c) K
Explanation: Potassium has the largest atomic radii among the given other options.
14) Which of the following elements would lose an electron easily ?
a) Mg
b) Na
c) K
d) Ca
Answer:- d) Na
Explanation: Sodium can lose electron easily as compared to others. Because it has only one electron in its outermost valence shell.
15) Which of the following elements does not lose an electron easily ?
a) Na
b) F
c) Mg
d) Al
Answer:- b) F
Explanation: Fluorine has 7 electrons in its outermost valance shell, which is hard to lose the electron in order it tries to take a electron and complete the octet. Other Na, Mg and Al has 1, 2 and 3 electrons in its outermost shell hence it loses electron easily.
16) Which of the following are the characteristics of isotopes of an element?
I) Isotopes of an element have
Same Atomic masses
II) Isotopes of an element have same Atomic number
III) Isotopes of an element show same physical properties
IV) Isotopes of an element show same chemical properties
a) I, III and IV
b) II , III and IV
c) II and III
d) II and IV
Answer:- d) II and IV
Explanation: Isotopes of the element are those which have same atomic number but different atomic masses. These is the main characteristics of the Isotopes of element.
17) Arrange the following elements in the order for their decreasing metallic character
Na, Si, Cl, Mg, Al
a) Cl > Si > Al > Mg > Na
b) Na > Mg > Al > Si > Cl
c) Na > Al > Mg > Cl > Si
d) Al > Na > Si >Ca > Mg
Answer:- b) Na > Mg > Al > Si > Cl
Explanation: These is the correct sequence of decreasing metallic character of elements. Sodium has more metallic character than Mg, Al, Si and Cl which finally comes upon the non metallic character.
18) Arrange the following elements in order of their increasing non- metallic character
Li, O ,C , Be , F
a) F< O < C < Be < Li
b) Li < Be < C < O <F
c) F < O < C < Be < Li
d) F < O < Be < C < Li
Answer:- b) Li < Be < C < O < F
Explanation: Here, b) is the correct increasing order of the non- metallic character. Lithium shows less metallic character while it goes increasing towards the fluorine which shows the maximum non- metallic character.
.19) What type of oxide would eka- aluminium form ?
a) EO3
b) E3O2
c) E2O3
d) EO
Answer:- c) E2O3
Explanation: Eka- aluminium oxide has the empirical formula E2O3.
20) Three elements B, Si and Ge are
a) Metals
b) Non- metal
c) Metalloids
d) Metal, Non-metal , and metalloid respectively.
Answer:- c) Metalloids
Explanation: These all elements belongs to the group metalloids.
21) Which of the following elements will form an acidic oxide ?
a) An element with atomic number 7
b) An element with Atomic number 3
c) An element with Atomic number 12
d) An element with Atomic number 19
Answer:- a) An element with atomic number 7
Explanation: Basically Non- metal forms the acidic oxides. Hence the element should be non-metal. The atomic number 7 will have electronic configuration 2,5 after gaining 3 electrons it will become electronegative. Hence it will be Non- metal.
22) The element with Atomic number 14 is hard and forms acidic oxide and a covalent halide. To which of the following categories does the element belong?
a) Metal
b) Metalloid
c) Non – metal
d) Left – hand side element
Answer:- b) Metalloid
Explanation: The element is silicon which has 14 Atomic number. These belongs to the metalloid group. Metalloids has both the characteristics of metals and Non-metals. Thus it forms acidic oxide as Non-metals and forms covalent halide like metals.
23) Which of the following depict the correct representation of atomic radius (R) of an atom ?
a) I and II
b) II and III
c) III and IV
d) I and IV
Answer:- b) II and III
Explanation: The distance between the nucleus of the element to the outermost orbit of it is known as atomic Radius. Which is correctly shown in the figure II and III.
24) Which one of the following does not increase while moving down the group of the periodic ?
a) Atomic radius
b) Metallic character
c) Valence
d) Number of shells in an element
Answer:- c) Valence
Explanation: Atomic radius, metallic character and numbers of shell increase while moving down the group of the periodic table but valencies remains constant.
25) On moving from left to right in a periodic table, the size of the atom.
a) Increases
b) Decreases
c) Does not change appreciably
d) First decreases and then increases
Answer:- b) Decreases
Explanation: On moving from left to right In a periodic table, the size of the atom decreases, because atomic radius decreases moving from left to right.
26) Which of the following set of elements is written in order of their increasing metallic character ?
a) Be Mg Ca
b) Na Li K
c) Mg Al Si
d) C O N
Answer:- a) Be Mg Ca
Explanation: Set a) is written in increasing metallic character. Because metallic character increase down the group. And these all the elements belongs to the same group.
Short Answer Questions
27) The three elements A, B , and C with similar properties have atomic masses X, Y, And Z respectively. The mass of Y is approximately equal to the average mass of X and Z. What is such an arrangement of elements called as? Give one example of such a set of elements.
Answer:-
The arrangement in which three atoms having different Atomic masses, then the Average of atomicmasses of first element and Third element is approximately equal to the middle element. These arrangement is known as Döbereiner’s Triad.
For example –
Lithium, Sodium, potassium which have atomic masses respectively.
28) Elements have been arranged in the following sequence on the basis of their increasing atomic masses.
F, Na, Mg , Al , Si, P , S, Cl ,Ar , K
a) Pick two sets of elements which have similar properties.
Answer:- the sets of elements which have same properties are –
1) Halogens – F and Cl
2) Metals – Na, Mg , Al and K
b) The given sequence represents which law of classification of elements ?
Answer:- the sequence represents the Law of classification of elements of Mendeleev’s law of periodic Table.
29) Can the following groups of elements be classified as Dobereiner’s triad ?
a) Na, Si, Cl
b) Be, Mg , Ca
Atomic mass of Be 9; Na 23 ; Mg 24 ; Si 28 ; Cl 35 ; Ca 40
Explain by giving reason.
Answer:-
Döbereiner’s law is based on the law that the Atomic mass of 1st and 3rd element is average Atomic mass of the 2nd element. But all the elements should show the same properties. Here Be, Mg and Ca shows the Döbereiner’s tried. But the Na, Si, and Cl does not obey the law of same properties of elements. Hence these is not Döbereiner’s tried.
30) In Mendeleev’s periodic table elements were arranged in the increasing order of their atomic masses. However, Cobalt with atomic mass of 58.93 amu was placed before nickel having an atomic mass of 58.71 amu. Give reason for the same.
Answer:-
Mendeleev’s periodic table is based on the law of increasing Atomic number. Nickel have higher Atomic number than the Cobalt. The elements with the same characteristics have to be placed in same group. Thus, cobalt was placed before nickel, although it was having the higher atomic mass than nickel.
31) “Hydrogen occupies a unique position in Modern Periodic Table.” Justify the statement.
Answer:-
Hydrogen is kept on the number 1 in the modern periodic table of Mendeleev. These is because the Atomic number of the hydrogen is 1. Also it is placed in alkali group od elements because their properties are similar to each other they have only 1 Electron in its outermost orbit. Also it shows the properties of halogens. Hence the hydrogen is placed at the unique place in periodic table.
32) Write the formulae of chlorides of Eka- Silicon and Eka- aluminium, the elements predicted by Mendeleev.
Answer:-
The empirical formula of Chlorides of Eka – silicon is –ECl4
The empirical formula of Chlorides of Eka – Aluminiumis – ECl3
33) Three elements A, B, and C have 3,4 and 2 electrons respectively in their outermost shell. Give the group number to which they belong in the Modern Periodic Table. Also, Give their Valencies.
Answer:-
Here,
A belongs to the group number = 13
The valency of A = 3
B belongs to the group number = 14
The valency of B = 4
C belongs to the group number = 2
The valency of C = 2
34) If an element X is placed in group 14 , what will be Formula and the nature of bonding of its Chloride?
Answer:-
The element placed in the group 14 will give the formula of Chlorides ECl4. Also it will have the 4 electrons in it valence shell orbital. Hence the sharing of electrons will takes and ultimately gives the chemical bonding of the electron to form the compound.
35) Compare the radii of two species X and Y. Give reasons for your answer.
a) X has 12 protons and 12 Electrons
Answer:- the electronic configuration of these element is 2,8,2.
b) Y has 12 protons and 10 electrons
Answer:- the electronic configuration of these element is 2,8
Since, X has one more electron orbital in its energy level thus it’s atomic Radius will be bigger than y as y has one orbital less than x.
36) Arrange the following elements in increasing order of their atomic radii.
Answer:- Atomic radius is the distance between the nucleus and the outermost orbit of that element.
Hence the increasing order of the Atomic Radius of following elements are –
a) Li, Be, F , N
Answer:- Li > Be > F > N
b) Cl, At, Br , I
Answer:- Cl > Br > I >At
37) Identify and name the metals out of the following elements whose electronic configuration are given below.
a) 2, 8, 2
Answer:- the element having the electronic configuration 2,8,2 is Magnesium.
b) 2, 8, 1
Answer :- the element having the electronic configuration 2,8,1 is Sodium
c) 2, 8, 7
Answer:- the element having the electronic configuration 2,8,7 is Chloride
d) 2,1
Answer:- the element having the electronic configuration 2,1 is lithium.
38) Write the formula of the product formed when the element A ( Atomic number 19) combines with the element B ( atomic number 17). Draw it’s electronic dot structure. What is the nature of the bond formed ?
Answer:-
Here,
The element A having Atomic number 19 is potassium (K)
The element B having Atomic number 17 is Chloride (Cl)
The electronic configuration of Potassium (K) = 2,8,8,1
As it has only 1 Electron in its outermost orbit thus it confirms that it is a metal.
The electronic configuration of Chloride (Cl) is = 2,8,7
As it has 7 electrons in its valence shell hence it must be Non – metal. As they are metal and a non-metal, thus two elements can combine by forming a ionic bond. That is exchange of electrons between them . Also known as sharing of electrons. Then it forms the compound potassium chloride (KCl) .
The electronic dot structure of the compound is as follows –
39) Arrange the following elements in the increasing order of their metallic character
Mg, Ca, K, Ge, Ga
Answer:-
The correct increasing order of the metallic character of given elements is –
Ge> Ga > Mg > Ca > K
40) Identify the elements with the following property and arrange the. In increasing order of their reactivity.
a) An element which is a soft and reactive metal
Answer:- The soft and reactive metal is Sodium.
b) The metal which is an important Constituent of limestone
Answer:- the important Constituent of the limestone is the element Calcium.
c) The metal which exists in liquid state at room temperature
Answer:- the metal which exists in liquid state at room temperature is Mercury.
41) Properties of the elements are given below. Where would you locate the following elements in the periodic table?
a) A soft metal stored under kerosene
Answer:- Sodium is a soft metal which is very reactive when get exposed to the air thus it is stored under the kerosene. Which belongs to the Group 1 and period 3.
b) An element with variable ( more than one) valency stored under water.
Answer:- the element with variable Valency stored under water is Phosphorus. Which belongs to the group 15 and period 3.
c) An element which is tetravalent and forms the basis of organic chemistry
Answer:- The important Constituent of the Organic chemistry is Carbon. Which belongs to the group 14 and period 2.
d) An element which is an inert gas with Atomic number 2
Answer:- The inert gas having at. Number 2 is Helium. It belongs to the group 18 and period 1.
e) An element whose thin oxide layer is used to make other elements Corrosion resistant by the process of “Anodising”
Answer:- the element used for the process of anodising is Aluminium. These belongs to the group 13 and period 3.
Long Answer Questions
43) An element is placed in 2nd group and 3rdperiod of the periodic, burns in presence of oxygen to form a basic oxide.
a) Identify the element
Answer:- the element is Magnesium.
b) Write the electronic configuration
Answer:- the electronic configuration of magnesium is 2,8,2.
c) Write the balanced equation when it burns in the presence of air
Answer:- when the magnesium burns in the presence of air it forms the magnesium oxide.
The reaction carried out as follows –
2Mg + O2 → 2MgO
d) Write a balanced equation when this oxide is dissolved in water
Answer:- When the magnesium oxide dissolved in water it gives the following reaction-
MgO + H2O → Mg(OH)2
e) Draw the electron dot structure for the formation of this oxide
Answer:-
The electron dot structure of the magnesium oxide is –
44) An element X ( atomic number 17) reacts with an element Y ( atomic number 20) to form a divalent
a) Where in the periodic table are elements X and Y placed?
Answer:-
- X has atomic number 17 hence X is = Chlorine
which is placed in the group 17 and period 3.
- Y has Atomic number 20 hence Y is = Calcium
Which is placed in the group 2 and period 4.
b) Classify X and Y as metal (s), Non metal (s) or metalloid (s)
Answer:- X = Chlorine is Non metal
Y = Calcium is Metal.
c) What will be the nature of oxide of element Y ? Identify the nature of bonding in the compound formed
Answer:-
Generally Metals form basic oxides hence Y will form a basic oxide and the nature of bonding in the compound will be ionic.
d) Draw the electron dot structure of the divalent halide.
Answer:-
The electron dot structure of the divalent halide is as follows –
44) Atomic number of a few elements are given below
10, 20, 7, 14
a) Identify the elements
Answer:-
The element with Atomic number –
10 = Neon
20 = Calcium
7 = Nitrogen
14 = Silicon
b) Identify the Group number of these elements in the periodic table
Answer:-
The group number of these elements in periodic table are –
Neon = Group 18
Calcium = Group 2
Nitrogen = Group 7
Silicon = Group 14
c) Identify The period of these elements in the periodic table
Answer:-
Neon = period 2
Calcium = period 3
Nitrogen = period 2
Silicon = period 3
d) What would be the electronic configurations for each of these elements ?
Answer:-
The electronic configuration of these elements are as follows –
Neon (10) = 2,8
Calcium (20) = 2,8,8,2
Nitrogen (7) = 2,5
Silicon (14) = 2,8,4
e) Determine the valency of these elements
Answer:-
The valencies of these elements are –
Neon = 0
Calcium = 2
Nitrogen = 3
Silicon = 4
45) Complete the following cross word puzzle (fig. 5.1)
Across
1 An element with Atomic number 12.
3 metal used in making cans and member of Group 14.
4 A lustrous Non-metal which has 7 electrons in its outermost shell.
Down–
2 highly reactive and soft metal which imparts yellow colour when subjected to flame and is kept in kerosene.
5 the first element of second period
6 an element which is used in making fluorescent bulbs and is second member of group 18 in the Modern Periodic Table.
7) a radioactive element which is the last member of halogen family
8) metal which is an important Constituent of steel And forms rust when exposed to moist air
9) the first metalloid in modern periodic table whose fibres are used in making bullet proof vests.
Answer:-
46)
Fig. 5.2
A) in this ladder ( fig. 5.2 ) symbols of elements are jumbled up. Rearrange these symbols of elements in the increasing order of their Atomic number in the periodic table.
Answer:-
The correct arrangement of these elements in their increasing order of the atomic number according to the periodic table is as follows –
H = 1
He = 2
Li = 3
Be = 4
B = 5
C = 6
N = 7
O = 8
F = 9
Ne = 10
Na= 11
Mg = 12
Al = 13
Si = 14
P = 15
S = 16
Cl = 17
Ar = 18
K = 19
Ca = 20
B) arrange them in the order of this group also.
Answer:-
The arrangement of these elements according to the group is as follows –
Group 1 = H, Li, Na , K
Group 2 = Be, Mg, Ca
Group 13 = B, Al
Group 14 = C, Si
Group 15 = N,P
Group 16 = O, S
Group 17 = F, U
Group 18 = He, Ne, Ar
47) Mendeleev’s predicted the existence of certain elements not known at that time and named two of them as Eka – silicon and eka – aluminium.
a) Name the elements which have taken the place of these elements.
Answer:-
The elements which have taken the place of these elements are –
Eka silicon = Germanium
Eka aluminium = Gallium
b) Mention the group and the period of these elements in the modern periodic table.
Answer:-
The group and the period of these elements in the modern periodic table are-
- Germanium = Group 14 , period 5
- Gallium = Group 13, period 5
c) Classify these elements as metals, Non- metals, metalloids
Answer:-
Germanium belongs to Metalloid
Gallium belongs to Metal
d) How many valence electrons are present in each one of them ?
Answer:-
The valence electrons present in these elements are
Germanium = 4 electrons
Gallium = 3 Electrons
48) A) electropositive nature of the element (s) increases down the group and decreases across the period
B) electronegativity of the element decreases down the group and increase across the period
C) atomic size increase down the group and decreases across a period (left to right)
D) metallic character increase down the group and decreases across a period
On the basis of the above periodic table, answer the following about the elements with atomic numbers 3 to 9.
A) Name the most electropositive element among them
Answer:- the most electropositive element among them is Lithium.
B) Name the most electronegative element
Answer:- the most electronegative element is Fluorine.
C) Name the element with smallest atomic size
Answer:- the element which has smallest atomic size is Fluorine.
D) Name the element which is a metalloid
Answer:- the element which is metalloid is Boron.
E) Name the element which shows maximum Valency.
Answer:- the element which shows maximum Valency is Carbon.
49) An element X which is a yellow solid at room temperature shows catenation and allotropy. X forms two oxides which are also formed during the thermal decomposition of ferrous sulphate crystals and are the major air pollutants.
a) Identify the element X
Answer:- X element will be Sulphur.
Which is a yellow solid. Which has Atomic number 16.
b) Write the electronic configuration of X
Answer:- the electronic configuration of Sulphur atomic number 16 is
K L M : 2, 8, 6
c) Write the balanced chemical equation for the thermal decomposition of ferrous sulphate crystals ?
Answer:- the balanced chemical equation for the thermal decomposition of ferrous sulphate crystals will be –
d) What would be the nature (acidic/basic) of oxides formed?
Answer:-
The Nature of the oxide formed is Acidic. Because Sulphur is Non metal. And non metal generally form Acidic oxides.
e) Locate the position of the element in the Modern Periodic Table ?
Answer:- Sulphur has atomic number 16 these belongs to the group 16 and period 3.
50) An element X of group 15 exists as diatomic molecule and combines with hydrogen at 773 K in presence of the catalyst to form a Compound, ammonia which has a characteristic pungent smell.
a) Identify the element X, how many valence electrons does it have ?
Answer:- the element X is Nitrogen. It has atomic number 7.
Hence the electronic configuration 2,5. And 5 valance electron in its outermost shell.
b) Draw the electrons dot structure of the diatomic molecule of X. What type of bond is formed in it ?
Answer:- the electron dot structure of diatomic molecule of nitrogen is –
It forms the triple Covalent bonds.
c) Draw the electron dot structure for Ammonia and what type of bond is formed in it ?
Answer:-
It forms the three Covalent bonds with 1 nitrogen and 3 Hydrogen.
The electron dot structure is as follows –
51) Which group of elements could be placed in Mendeleev’s periodic Table without disturbing the original order ? Give reason.
Answer:-
Inert gases which is also known as Nobel gases these could be placed in Mendeleev’s periodic table without disturbing the original order. These Nobel gases contains the gases like Helium, neon, argon, Krypton, etc. When the periodic table was made by Mendeleev that time only 63 elements were known. But Mendeleev left some gaps for the elements which will be discovered later on. The noble gases known later was kept in separate group because they have same chemical properties. These shows that the new elements could easily adjust in the Mendeleev’s periodic table without disturbing the original order of the table.
52) Give an account of the process adopted by Mendeleev’s for the classification of elements. How did he arrive at “periodic law” ?
Answer:-
Mendeleev’s periodic table was based on the classification of elements according to their atomic number and their similar chemical properties. When the Mendeleev made periodic table that time only 63 elements were known. Which was having some atomic number, atomic masses and chemical properties. He made 63 cards wrote names of the element on them and their chemical properties, then he put it on the wall.
Then he observed the similarity between them, he noticed that the many of them were arranged with the increasing atomic masses. Thus he made the law. Which was Properties of the elements are periodic function of their increasing masses. Hence he came upon the periodic law of elements.