Assignment for Class 10 Chemistry Chapter 5 Periodic Classification Of Elements
Class 10 Chemistry students should refer to the following printable assignment in Pdf for Chapter 5 Periodic Classification Of Elements in standard 10. This test paper with questions and answers for Grade 10 Chemistry will be very useful for exams and help you to score good marks
Chapter 5 Periodic Classification Of Elements Class 10 Chemistry Assignment
1-MARK QUESTIONS
Question : Mention one reason why elements should be classified?
Question : Write two reasons responsible for late discovery of noble gases .
Question : Chlorine, Bromine and Iodine form a Dobereiner’s triad. The atomic masses of chlorine and iodine are 35.5 and 126.9 respectively. Predict the atomic mass of bromine.
Question : Who proposed the law of octaves? Mention its one limitation.
2-MARKS QUESTIONS
Question : State and explain the Mendeleev’s Periodic Law and Modern Periodic Law. Also state the basis of classification for the two laws mentioned above.
Question : State the merits and demerits of Mendeleev’s Periodic Law. How are the position of isotopes decided in the modern periodic table?
Question : What would be the nature of the oxides formed by the elements on the left hand side of the periodic table? How many valence electrons do these elements have?
Question : Based on electronic configuration, how will you identify the first and the last element of a period.
Objective Questions :
Question. Identify the correct statements.
(i) In Mendeleev’s periodic table, elements were arranged in the order of their increasing atomic masses and it was also observed that there occurs a periodic recurrence of elements with similar physical and chemical properties.
(ii) In 1913, Dmitri Ivnovich Mendeleev showed that the atomic number of an element is more fundamental property than its atomic mass.
(iii) He was the most important contributor to the early development of a Periodic Table of elements wherein the elements were arranged on the basis of their fundamental property, the atomic mass and also on the similarity of chemical properties.
(iv) Among chemical properties, Mendeléev concentrated on the compounds formed by elements with oxygen and hydrogen.
(v) Mendeléev formulated a Periodic Law, which states that ‘the properties of elements are the periodic function of their atomic numbers’.
(vi) Mendeléev’s Periodic Table contains vertical columns called ‘groups’ and horizontal rows called periods.
(a) (ii) and (v)
(b) (i), (iii), (iv), (v) and (vi)
(c) (i), (iii), (iv) and (vi)
(d) All the statements are correct.
Answer : C
Question. Which of the given pairs of atomic numbers represents elements in the same group?
(a) 11, 19
(b) 6, 12
(c) 4, 16
(d) 8, 17
Answer : A
Question. In the Modern Periodic Table, calcium (Z = 20) is surrounded by the elements with atomic numbers 12, 19, 21 and 38. Which of the following will have physical and chemical properties resembling calcium? 
(a) 12, 38
(b) 12, 19, 38
(c) 19, 38
(d) 12, 19
Answer : A
Question. Which of the following will have equal number of electrons?
(a) Cl– and Br–
(b) Na+ and Mg2+
(c) Ar and Ne
(d) Mg2+ and Ca2+
Answer : B
Question. Element X has a proton number equal to 17. Which of the following statements about X is not correct?
(a) X is a member of Group VII.
(b) X has 7 electrons in the outermost electron shell.
(c) X has three occupied electron shells.
(d) X gains one electron to form X +.
Answer : D
Question. Moving across a period of the Periodic Table,
(a) the elements become more electronegative
(b) the metallic character of the elements increases.
(c) the ability of the elements to lose electrons increases.
(d) the elements form ions with increasing negative charge.
Answer : A
Question. Which of the following is the most nonmetallic element?
(a) Br
(b) Cl
(c) P
(d) S
Answer : B
Question. The effective nuclear charge acting on the valence shell electrons
(a) increases across a period
(b) decreases down the group
(c) both (a) and (b)
(d) none of the above.
Answer : C
Question. The basic character of MgO, SrO, K2O and NiO increases in the order
(a) K2O < SrO < MgO < NiO
(b) NiO < MgO < SrO < K2O
(c) MgO < NiO < SrO < K2O
(d) K2O < MgO < NiO < SrO
Answer : B
Question. The position of elements A and B are shown in the periodic table below: 
Which of the following statements is correct about the two elements?
(a) A and B have the same electron structure.
(b) A and B have the same number of filled electron shells.
(c) A is a metal and B is a non-metal.
(d) A is in period 2 and B is in group III.
Answer : C
Question. Element X is in period 3 and group III of the periodic table. The electronic configuration of X is
(a) 2, 1
(b) 2, 3
(c) 2, 8, 3
(d) 2, 8, 5
Answer : C
Question. Which of the following combination of elements belong to the same group?
(a) N, P, As
(b) Li, Be, Al
(c) Na, Mg, Al
(d) O, S, Cl
Answer : A
Question. From top to bottom in a group of the periodic table the electropositive character of the element
(a) increases
(b) decreases
(c) remains unchanged
(d) changes irregularly.
Answer : A
Question. Which of the following statements is correct about elements 19 9A and 3717B?
(a) A is more electronegative than B.
(b) A forms a positive ion and B forms a negative ion.
(c) A and B have the same number of neutrons.
(d) A and B have the same number of electrons.
Answer : A
Question. Two elements A and B belong to group 1 and 2 respectively. Identify the correct statements.
(i) Valency of A is one while that of B is two.
(ii) Oxide of A has formula AO and that of B is B2O
(iii) Element A is more metallic as compared to element B.
(iv) Element A is smaller than B in size.
(a) (ii) and (iv)
(b) (i) and (iv)
(c) (i) and (iii)
(d) (ii) and (iv)
Answer : C
Question. Which of the following elements is a metalloid?
(a) Pb
(b) Sb
(c) Bi
(d) Zn
Answer : B
Question. Döberiener’s system of classification into triads was not found to be useful as he could identify only
(a) two triads
(b) three triads
(c) four triads
(d) five triads.
Answer : B
Question. From the given set of metals and non-metals identify the non-metals. S, Mg, Al, P, N, Na, K.
(a) S, P, K
(b) Mg, Al, Na
(c) S, P, N
(d) S, Al, K
Answer : C
(a) Both assertion and reason are true, and reason is correct explanation of the assertion.
(b) Both assertion and reason are true, but reason is not the correct explanation of the assertion.
(c) Assertion is true, but reason is false.
(d) Assertion is false, but reason is true.
Question. Assertion : Decreasing order of atomic radii is : Cl > F > O > S.
Reason : Atomic radius increases as the number of energy level increases and decreases as nuclear charge increases.
Answer : D
Question. Assertion : Down the group, atomic radius increases.
Reason : Electrons are added in new shell.
Answer : A
Question. Assertion : Increasing order of metallic character is : P < Si < Be < Mg < Na
Reason : Metallic character increases along a period and decreases down a group.
Answer : C
Question. Assertion : Alkali metals do not form dipositive ions.
Reason : After loss of one electron alkali metals achieve stable configuration of noble gas.
Answer : A
Question. Assertion : Atomic radius in general decreases along a period.
Reason : In a period, effective nuclear charge decreases.
Answer : C
Question. Assertion : In Dobereiner’s triad, the three elements present have same gaps of atomic numbers.
Reason : Elements in a triad have similar properties.
Answer : D
Very Short Answers
Answer : It states that “the properties of the elements are periodic functions of their atomic numbers.”
Question : State one reason for placing Mg and Ca in the same group of the periodic table.
Answer : They have same number of valence electrons.
Question : What was the drawback of these two laws?
Answer : All the elements discovered at that time could not be classified.
Question : Lithium, sodium and potassium form a Dobereiner’s triad. The atomic masses of lithium and potassium are 7 and 39 respectively. Predict the atomic mass of sodium.
Answer : Atomic mass of Na 7 + 39 / 2 = 46/2 = 23
Question : Chlorine, bromine and iodine form a Dobereiner’s triad. The atomic masses of chlorine and iodine are 35.5 and 126.9 respectively. Predict the atomic mass of bromine.
Answer : Atomic mass of Br 35.5 + 126.9 / 2 = 162.4 / 2 = 81.2
Question : What was the basis of classification of elements by Newland?
Answer : Increasing order of atomic mass
Question : What were the limitations of Dobereiner’s classification ?
Answer : Dobereiner could identify only three triads from the elements known at that time. Hence, this system of classification into triads was not found useful.
Question : Name any three metalloids
Answer : Boron, Silicon and Germanium.
Question : Why was the system of classification of elements into triads not found suitable?
Answer : It is because all the elements discovered at that time could not be classified into triads.
Short Answers
Question : In the modern periodic table, the element Calcium (atomic number = 20) is surrounded by elements with atomic numbers 12, 19, 21 and 38. Which of these elements has physical and chemical properties resembling those of Calcium and why?
Answer : Elements with atomic number 12, 38 resemble calcium in physical and chemical properties because they have same number of valence electrons and belong to same group 2.
Mg(12) : 2, 8, 2
Ca(20) : 2, 8, 8, 2
Sr(38) : 2, 8, 18, 8, 2
Question : How does the valency of elements vary
(a) in going down a group, and
(b) in going from left to right in a period of the periodic table?
Answer : (a) Valency remains the same in a group.
(b) Valency first goes on increasing from left to right in a period till middle of period, then decreases.
Question : An element ‘M’ has atomic number 11.
(a) Write its electronic configuration.
(b) State the group to which ‘M’ belongs.
(c) Is ‘M’ a metal or a non-metal?
(d) Write the formula of its chloride.
Answer :
Question : Give reasons:
(a) Elements in a group have similar chemical properties.
(b) Elements of Group I form ions with a charge of +1.
Answer : (a) Elements in a group have same number of valence electrons and same valency therefore have similar chemical properties.
(b) It is because elements of group 1 lose one electron to acquire +1 charge and become stable.
Question : How does the metallic character of elements change along a period of the periodic table from the left to the right and why?
Answer : The metallic character goes on decreasing along a period from left to right because atomic size goes on decreasing therefore, tendency to lose electrons decreases.
Question : Choose from the following: 6C, 8O, 10Ne, 11Na,14Si
(a) Elements that should be in the same period.
(b) Elements that should be in the same group.
State reason for your selection in each case.
Answer : (a) 6C, 8O, 10Ne are in same period, Le. 2nd period as they have two shells. nNa and 14Si are in same period, i.e. 3rd period as they have three shells.
(b) 6C,14Si are in same group because they have same number of valence electrons, i.e. four.
Question : An element ‘X’ has atomic number 13.
(a) Write its electronic configuration.
(b) State the group to which ‘X’ belongs.
(c) Is ‘X’ a metal or a non-metal?
(d) Write the formula of its bromide.
Answer :
.
Question : In the periodic table, how does the tendency of atoms to lose electrons change on going from
(a) left to right across a period?
(b) top to bottom in a group?
Answer : (a) Tendency to lose electrons decreases from left to right across a period.
(b) Tendency to lose electrons increases from top to bottom in a group.
Question : State the Modern Periodic Law for classification of elements. How many
(a) groups and (b) periods are there in the Modern Periodic Table?
Answer : ‘Properties of elements are the periodic function of their atomic number.’
(a) There are 18 groups and
(b) 7 periods in the Modern Periodic Table.
Question : The formula of its oxide An element ‘M’ has atomic number 12.
(a) Write its electronic configuration.
(b) State the group to which ‘M’ belongs.
(c) Is ‘M’ a metal or a non-metal?
(d) Write the formula.
Answer :
Long Answers
Question : Point out the major defects in the Mendeleev's Periodic Table.
Answer : Defects in Mendeleev's Periodic Table
The Mendeleev's periodic table was quite helpful in the classification of the elements.
But it had certain defects also. These are discussed as follows:
i. Position of hydrogen: Hydrogen was placed at the top of group IA. It is a nonmetal where all other elements included in the group are metals.
ii. Position of isotopes: The periodic table is based on the basis of the atomic masses of the elements. This means that the elements with different atomic masses must be given separate place in the table. If this is correct, all the isotopes of an element must be allotted separate positions. For example, there are three isotopes for hydrogen and they must be given three separate places in the table.
But only one position for hydrogen has been given.
iii. Wrong order of atomic masses of some elements: In the table, the elements are arranged in order of increasing atomic masses. This means that the element with higher atomic mass must be placed after the element with the lower atomic mass. But in the table, there are some anomalies. For example, Co (Cobalt) with atomic mass 58.9 should be placed after Ni (Nickel) with atomic mass 58.7. But it has been placed before nickel.
iv. Elements with similar properties placed in different groups: In the periodic table, it has been found that the elements with similar properties are placed in different groups. For example, copper and mercury have many common properties. But copper has been placed in group I B and mercury in group II B.
v. No similarity in the elements placed in sub-groups: The elements present in different sub-groups of the same group are expected to have common properties. But these are quite different. For example, elements in group 1 A are very soft and reactive metals but element in group I B are hard and less reactive in nature.
vi. No explanation for the cause of periodicity: Mendeleev was not in a position to explain why the elements included in a group show similar properties.
vii. Position of lanthanides and actinides: Both these families have fourteen elements each, but they could not find proper positions in the main set up of the Mendeleef’s periodic table. Instead, these elements have been placed in two separate rows at the bottom of periodic table without assigning a proper reason.
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