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# Lakhmir Singh solutions for Class 10 Science chapter 5 - Periodic Classification Of Elements

## Chapter 5: Periodic Classification Of Elements

#### Chapter 5: Periodic Classification Of Elements solutions [Pages 281 - 285]

Q 1.1 | Page 281

On what basis did mandeleev arrange the elements in his periodic table?

Q 1.2 | Page 281

On what basis elements are arranged in periodi table now?

Q 2.1 | Page 281

State whether the following statement is true of false:

Newlands divided the elements into horizontal rows of eight elements each.

Q 2.2 | Page 281

State whether the following statement is true of false:

According to Mendeleev's periodic law, the properties of elements are a periodic function of their atomic numbers.

Q 2.3 | Page 281

State whether the following statement is true of false:

The elements in a group have consecutive atomic numbers.

Q 3 | Page 282

Name the Russian chemist who said that the properties of elements are a periodic function of their atomic masses.

Q 4.1 | Page 282

Rewrite the following statement after correction, if necessary:

Groups have elements with consecutive atomic numbers.

Q 4.2 | Page 282

Rewrite the following statement after correction, if necessary:

Periods are the horizontal rows of elements.

Q 4.3 | Page 282

Rewrite the following statement after correction, if necessary:

Isotopes are the elements of the same group.

Q 5.1 | Page 282

Name the scientist who gave the Law of octaves in the early classification of elements.

Q 5.2 | Page 282

Name the scientist who gave Law of triads in the early classification of elements.

Q 6 | Page 282

A, B and C are the elements of a Dobereiner's triad. If the atomic mass of A is 7 and the of C is 39, what should be the atomic mass of B?

Q 7 | Page 282

X and Y are the two elements having similar properties which obey Newland's laws of octaves. How many elements are there in-between X and Y?

Q 8 | Page 282

What was the Mendeleev's basis for the classification of elements?

Q 9 | Page 282

In the classification of the them known elements, Mendeleev was guided by two factors. What are those two factors?

Q 10 | Page 282

Name two elements whose properties were predicted on the basis fo their positions in Mendeleev's periodic table.

Q 11 | Page 282

The three elements predicted by Mendeleev from the gaps in his periodic table were known as eka-boron, eka-aluminimum and eka-silicon. What names were given to these elements when they were discovered later on?

Q 12 | Page 282

Name two elements whose properties were predicted on the basis fo their positions in Mendeleev's periodic table.

Q 13 | Page 282

State one example of a Dobereiner's triad, showing in it that the atomic mass of middle element is half-way between those of the other two.

Q 14 | Page 282

Which group of elements could be placed in Mendeleev's periodic table later on, without disturbing the order? Give reason.

Q 15.1 | Page 282

Fill in the following blank with suitable word:
The basis for modern periodic table is ...............

Q 15.2 | Page 282

Fill in the following blank with suitable word:
The horizontal rows  in a periodic table are called ...............

Q 15.3 | Page 282

Fill in the following blank with suitable word:

Group 1 elements are called ...............

Q 15.4 | Page 282

Fill in the following blank with suitable word:
Group 17 elements are known as ...............

Q 15.5 | Page 282

Fill in the following blank with suitable word:

Group 18 elements are called ...............

Q 15.6 | Page 282

Fill in the following blank with suitable word:

According to Newland's classification of elements, the properties of sulphur are similar to those of oxygen because sulphur is the ............... element starting from oxygen.

Q 16.1 | Page 282

What is meant by a group, in a periodic table?

Q 16.2 | Page 282

What is meant by a period, in a periodic table?

Q 16.3 | Page 282

How many periods and groups are there in the long form of periodic table?

Q 16.4 | Page 282

Give two example of group 1 elements.

Q 16.5 | Page 282

Give two example of group 17 elements.

Q 16.6 | Page 282

Give two example of group 18 elements.

Q 17.1 | Page 282

In the Modern Periodic Table, which are the metals among the first ten elements?

Q 17.2 | Page 282

What is the significance of atomic number in the modern classification of elements? Explain with the help of an example.

Q 18.1 | Page 282

How were the positions of isotopes of an element decided in the modern periodic table?

Q 18.2 | Page 282

How were the positions of cobalt and nickel resolved in the modern periodic table?

Q 18.3 | Page 282

where should hydrogen be placed in the modern periodic table? Give reason for your answer.

Q 19.1 | Page 282

On which side of the periodic table will you find metals?

Q 19.2 | Page 282

On which side of the periodic table will you find non-metals?

Q 19.3 | Page 282

What is the name of those elements which divide metals and non-metals in the periodic table?

Q 20.1 | Page 283

Name three elements that have a single electron in their outermost shells.

Q 20.2 | Page 283

Name two elements that have two electrons in their outermost shells.

Q 20.3 | Page 283

Name three elements with filled outermost shells.

Q 21 | Page 283

What is Debereiner's law of triads? Explain with the help of one example of a Dobereiner's triad.

Q 22 | Page 283

What is Newlands' law of octaves? Explain with an example.

Q 23.1 | Page 283

Q 23.2 | Page 283

What were the limitations of Dobereiner's classification of elements?

Q 23.3 | Page 283

What were the limitations of Newlands’ Law of Octaves?

Q 24.1 | Page 283

State the periodic law on which Mendeleev's periodic table table was based. Why and how was this periodic law changed?

Q 24.2 | Page 283

Explain why, the noble gases are placed in a separate group.

Q 25.1 | Page 283

State the merits of Mendeleev's classification of elements.

Q 25.2 | Page 283

Describe two anomalies of Mendeleev's periodic classification of elements.

Q 26.1 | Page 283

What name were given by Mendeleev to the then undiscovered element scandium.

Q 26.1 | Page 283

How do the properties of eka-aluminium element predicted by Mendeleev compare with the actual properties of gallium element?

Q 26.2 | Page 283

What name were given by Mendeleev to the then undiscovered element gallium?

Q 26.3 | Page 283

What name were given by Mendeleev to the then undiscovered element germanium?

Q 27.1 | Page 283

Why do we classify elements?

Q 27.2 | Page 283

What were the two criteria used by Mendeleev to classify the elements in his periodic table?

Q 27.3 | Page 283

Why did Mendeleev leave some gaps in his periodic table?

Q 27.4 | Page 283

In Mendeleev's periodic table, why was there no mention of noble gases like helium, neon and argon?

Q 27.5 | Page 283

Would you place the two isotopes of chlorine, CI-35 and CI-37 in different slots because of their different atomic masses or in the same slot because their chemical properties are the same? Justify your answer.

Q 28.1 | Page 283

State Mendeleev's periodic law.

Q 28.2 | Page 283

What chemical properties of elements were used by Mendeleev in creating his periodic table?

Q 28.3 | Page 283

State any three limitations of Mnedeleev's classification of elements.

Q 28.4 | Page 283

Besides gallium, which two other elements have since been discovered for which Mendeleev had left gaps in his periodic table?

Q 28.5 | Page 283

Which group of elements was missing from Mendeleev's original periodic table?

Q 29.1 | Page 283

State Modern periodic law

Q 29.2 | Page 283

How does the electronic configuration of an atom relate to its position in the Modern Periodic Table?

Q 29.3 | Page 283

How could the Modern Periodic Table remove various anomalies of Mendeleev’s Periodic Table?

Q 29.4 | Page 283

Is it possible to have an element having atomic number 1.5 placed between hydrogen and helium?

Q 29.5 | Page 283

Name the scientist who prepared modern periodic table.

Q 30 | Page 283

In Mendeleev's periodic table, gap was not left for one of the following elements. This element is:

(a) gallium
(b) beryllium
(c) germanium
(d) scandium

Q 31 | Page 283

The Newland's law of octaves for the classification of elements was not found to be applicable only up to the element:

(a) potassium
(b) calcium
(c) cobalt
(d) phosphorus

Q 32 | Page 283

According to Mendeleev's periodic law, the elements were arranged in the periodic table in the order of:

(a) decreasing atomic numbers
(b) increasing atomic numbers
(c) decreasing atomic masses
(d) increasing atomic masses

Q 33 | Page 283

The three elements having chemical symbols of Si, B and Ge are:

(a) all metals
(b) all non-metals
(c) all metalloids
(d) Si is metalloid, B is metal and Ge is non-metal

Q 34 | Page 284

In Mendeleev's periodic table, gaps were left for the elements to be discovered later on. An element which found a vacant place in the periodic table later on is:

(a) Be
(b) Si
(c) Ge
(d) Se

Q 35 | Page 284

The three imaginary elements X, Y and Z represent a Dobernener's triad. If the atomic mass of element X is 14 and that of element Y is 46, then the atomic mass of element Z will be:

(a) 28
(b) 60
(c) 78
(d) 72

Q 36 | Page 284

The atomic numbers of four elements P, Q, R and S are 6, 8, 14 and 16 respectively. Out of these, the element known as metalloid is:

(a) P
(b) Q
(c) R
(d) S

Q 37 | Page 284

Which of the following statement is correct in regard to the classification of elements?

(a) Elements in modern periodic table are arranged on the basis of increasing atomic masses.
(b) Elements in Mendeleev's periodic table are arranged on the basis of increasing atomic numbers.
(c) In modern periodic table, the element nickel of lower atomic mass is kept before the element cobalt of higher atomic mass.
(d) In modern periodic table, the isotopes of chlorine having different atomic masses are kept in the same group.

Q 38 | Page 284

Which of the following statement about the modern periodic table is correct?

(a) It has 18 horizontal rows known as periods.
(b) It has 7 vertical columns known as periods.
(c) It has 18 vertical columns known as groups.
(d) It has 7 horizontal rows known as groups.

Q 39 | Page 284

An element X forms an oxide X2O3. In which group of Mendeleev's periodic table is this element placed?

(a) group II
(b) group III
(c) group V
(d) group VIII

Q 40 | Page 284

The modern periodic table was prepared by:

(a) Dobereiner
(b) Newlands
(c) Bohr
(d) Mendeleev

Q 41 | Page 284

The atomic particle whose number in the atoms of an element always remains the same and which forms the real basis for the modern classification of elements is:

(a) electron
(b) proton
(c) neutron
(d) meson

Q 42 | Page 284

The atomic masses of three elements X, Y and Z having similar chemical properties are 7, 23 and 39 respectively.

(a) Calculate the average atomic mass of elements X and Z.
(b) How does the average atomic mass of elements X and Z compare with the atomic mass of element Y?
(c) Which law of classification of elements is illustrated by this example?
(d) What could the elements X, Y and Z be?
(e) Give another example of a set of elements which can be classified according to this law.

Q 43 | Page 284

In the following set of element, one element does not belong to the set. Select this element and state why it does not belong:
Calcium, Magnesium, Sodium, Beryllium

Q 44 | Page 284

In the following set of elements, one element does not belong to the set. Select this element and state why it does not belong:
Oxygen, Nitrogen, Carbon, Chlorine, Fluorine

Q 45 | Page 284

Can the following groups of elements be classified as Dobereiner's triads?

(a) Na, Si, Cl
(b) Be, Mg, Ca
(Atomic masses : Be 9 ; Na 23 ; Mg 24 ; Si 28 ; Cl 35.5 ; Ca 40)

Q 46.1 | Page 284

Consider the following elements:
Na, Ca, Al, K, Mg, Li

Which of these elements belong to the same period of the periodic table?

Q 46.2 | Page 284

Consider the following elements:
Na, Ca, Al, K, Mg, Li

Which of these elements belong to the same group of the periodic table?

Q 47.1 | Page 284

Which element has two shells, both of which are completely filled with electrons?

Q 47.2 | Page 284

Which element has the electronic configuration 2, 8, 2?

Q 47.3 | Page 284

Which element has a total of three shells, with four electrons in its valence shell?

Q 47.4 | Page 284

Which element has a total of two shells, with three electrons in its valence shell?

Q 47.5 | Page 284

Which element has twice as many electrons in its second shell as in its first shell?

Q 48 | Page 285

Consider the following elements:
Ca, Cl, Na, I, Li, Ba, Sr, K, Br

Separate these elements into three groups (families) of similar properties. State one property in each case on the basis of which you have made your choice.

Q 49 | Page 285

Mendeleev predicted the existence of certain elements not known at that time and named two of them as eka-aluminium, and eka-silicon.

(a) Name the element which has taken the place of (i) eka-aluminium, and (ii) eka-silicon
(b) Mention the period/periods of these elements in the modern periodic table.
(c) Write the group/ groups of these elements in the modern periodic table.
(d) Classify these elements as metals, non-metals or metalloids.
(e) How many valence electrons are present in the atoms of each of these elements?

Q 50 | Page 285

A part of the early classification of elements has been given below:

 H Li Be B C N O F Na Mg Al Si P S

(a) Which law of classification of element is illustrated by the above arrangement of elements?
(b) Name the scientist who proposed such a classification of elements.
(c) Why is such a classification of elements compared with a characteristics of musical scale?
(d) State one limitation of this classification of elements.

#### Chapter 5: Periodic Classification Of Elements solutions [Pages 302 - 308]

Q 1 | Page 302

Give alongside is a part of the periodic table :
As we move horizontally from left to right:

 Li Be B C N O F Na Mg Al Si P S Cl

(i) What happens to the metallic character of the elements?
(ii) What happens to the atomic size?

Q 2 | Page 302

How would the tendency to gain electrons change on moving from left to right in a period of the periodic table?

Q 3 | Page 302

How would the tendency to lose electrons change as we go from left to right across a period of the periodic table?

Q 4.1 | Page 303

How does the chemical reactivity of alkali metals vary on going in group 1 of the periodic table?

Q 4.2 | Page 303

How does the chemical reactivity of the halogens vary on going in group 17 of the periodic table?

Q 5 | Page 303

What property do all elements in the same column of the Periodic Table as boron have in common?

Q 6 | Page 303

What property do all elements in the same column of the Periodic Table as fluorine have in common?

Q 7.1 | Page 303

What is the number of valence electrons in the atoms of first elements in a period?

Q 7.2 | Page 303

What is the usual number of valence electrons in the atoms of the last element in a period?

Q 8 | Page 303

State whether the following statement is true or false:
On going down in a group of the periodic table, the number of valence electrons increases.

Q 9 | Page 303

What is the major characteristic of the first elements in the periods of the periodic table? What is the general name of such elements?

Q 10 | Page 303

How do the atomic radii of elements change as we go from left to right in a period of the periodic table?

Q 11 | Page 303

What happens to the metallic character of the elements as we go down in a group of the periodic table?

Q 12.1 | Page 303

How does the number of valence electrons vary on moving from left or right in the first period of the periodic table?

Q 12.2 | Page 303

How does the number of valence electrons vary on moving from left or right in the second period of the periodic table?

Q 13 | Page 303

How does the valency of elements change of moving from left to right in the third period of the periodic table?

Q 14 | Page 303

How does the valency of elements vary in going down a group of the periodic table?

Q 15.1 | Page 303

Name the element which is in  first group and third period.

Q 15.2 | Page 303

Name the element which is in seventeenth group and second period.

Q 16 | Page 303

How do electronic configurations of elements change in second period of periodic table with increase in atomic numbers?

Q 17 | Page 303

Arrange the following elements in increasing order of their atomic radii:
Li, Be, F, N

Q 18 | Page 303

Arrange the following elements in the increasing order of their metallic character:
Mg, Ca, K, Ga

Q 19.1 | Page 303

Rewrite the following statement after correction, if necessary:

Elements in the same period have equal valency

Q 19.2 | Page 303

Rewrite the following statement after correction, if necessary:

The metallic character of elements in a period increases gradually on moving from left to right.

Q 20.1 | Page 303

Fill in the following blank with suitable word:
The horizontal rows  in a periodic table are called ...............

Q 20.2 | Page 303

Fill in the blank in the following statement:

In going across a period (right to left) in periodic table, the atomic size of the atom ...............

Q 20.3 | Page 303

Fill in the blank in the following statement:

On moving form right to left in the second period, the number of valency electrons ...............

Q 20.4 | Page 303

Fill in the blank in the following statement:

On going down in a group in the periodic table, the metallic character of elements ...............

Q 20.5 | Page 303

Fill in the blank in the following statement:

The tendency to gain an electron ............... on moving down in a group of the periodic table.

Q 21 | Page 303

Nitrogen (atomic number 7) and phosphorus (atomic number 15) belong to group 15 of the periodic table. Write the electronic configuration of these two elements. Which of these will be more electronegative? Why?

Q 22 | Page 303

An element X belongs to group 2 and another element Y belongs to group 15 of the periodic table:

(a) What is the number of valence electron in X?
(b) What is the valency of X?
(c) What is the number of valence electrons in Y?
(d) What is the valency of Y?

Q 23.1 | Page 303

What is a period in a periodic table?

Q 23.2 | Page 303

How do atomic structures (electron arrangements) change in a period with increase in atomic numbers from left to right?

Q 23.3 | Page 303

How does Chemical reactivity of elements change on going from left to right in a period of the periodic table?

Q 23.4 | Page 303

How does Nature of oxides of elements change on going from left to right in a period of the periodic table?

Q 24.1 | Page 303

How does the size of atoms (atomic size) generally vary in going from left to right in a period of the periodic table? Why does it vary this way?

Q 24.2 | Page 303

What happens to the metallic character of the elements as we move from left to right in a period of the periodic table?

Q 25.1 | Page 304

Explain why All the elements of a group have similar chemical properties.

Q 25.2 | Page 304

Explain why All the elements of a period have different chemical properties.

Q 25.3 | Page 304

The atomic radii of three elements X, Y and Z of a period of the periodic table are 186 pm; 104 pm and 143 pm respectively. Giving a reason, arrange these elements in the increasing order of atomic numbers in the period.

Q 26.1 | Page 304

How does the electropositive character of elements change on going down in a group of the periodic table?

Q 26.2 | Page 304

State how the valency of elements varies in a group of the periodic table?

Q 26.3 | Page 304

State how the valency of elements varies in a period of the periodic table?

Q 27.1 | Page 304

What is the fundamental difference in the electron configurations between the group 1 and group 2 elements?

Q 27.2 | Page 304

On the basis of electronic configuration, how will you identify chemically similar elements?

Q 27.3 | Page 304

On the basis of electronic configuration, how will you identify the first element of a period?

Q 28.1 | Page 304

What is the usual number of valence electrons and valency of group 18 elements of the periodic table?

Q 28.2 | Page 304

What happens to the number of valence electrons in the atoms of elements as we go down in a group of the periodic table?

Q 29.1 | Page 304

What is the main characteristic of the last elements in the periods of the periodic table? What is the general name of such elements?

Q 29.2 | Page 304

What is the number of elements is 1st period the modern periodic table?

Q 29.3 | Page 304

(b) What is the number of elements is 3rd period, the modern periodic table?

Q 30.1 | Page 304

How does the atomic size vary on going down from top to bottom in a group of the periodic table? Why does it vary this way?

Q 30.2 | Page 304

Lithium, sodium, potassium are all metals that react with water to liberate hydrogen gas. Is there any similarity in the atoms of these elements?

Q 31.1 | Page 304

How does the tendency to lose electrons change as we go down in group 1 of the periodic table? Why does it change this way?

Q 31.2 | Page 304

How does the tendency to gain electrons change as we go down in group 17 of the periodic table? Why does it change this way?

Q 32.1 | Page 304

Why does the size of the atoms progressively become smaller when we move from sodium (Na) to chlorine (Cl) in the third period of the periodic table?

Q 32.2 | Page 304

Helium and neon are unreactive gases. What, if anything, do their atoms have in common?

Q 33.1 | Page 304

In the modern Periodic Table, why does cobalt with higher atomic mass of 58.93 appear before nickel having lower atomic mass of 58.71?

Q 33.2 | Page 304

Why could no fixed position be given to hydrogen in Mendeleev's periodic table?

Q 34.1 | Page 304

What are the periods in a periodic table? Give two characteristics of each.

Q 34.2 | Page 304

What are the groups in a periodic table? Give two characteristics of each.

Q 34.3 | Page 304

In terms of electronic configurations, explain the variation in the size of the atoms of the elements belonging to the same period and same group ?

Q 34.4 | Page 304

Given alongside is a part of the periodic table. As we move vertically downward from Li to fr?

 Li Be Na K Rb Cs Fr rA Ra

What happens to the size of atoms?

Q 34.5 | Page 304

Given alongside is a part of the periodic table. As we move vertically downward from Li to Fr:

 Li Be Na K Rb Cs Fr Ra

What happens to their metallic character?

Q 34.6 | Page 304

Name two properties of elements whose magnitudes change when going from top to bottom in a group of the periodic table. In what manner do they change?

Q 34.7 | Page 304

Rewrite the following statement after correction, if necessary:

Groups have elements with consecutive atomic numbers.

Q 35.1 | Page 305

Explain why, the first period of the periodic table has only two elements whereas second period has eight elements

Q 35.2 | Page 305

Why do elements in the same group show similar properties but the elements in different groups show different properties?

Q 35.3 | Page 305

For each of the following triads, name the element with the characteristics specified below:

 Elements Least atomic radius Chemically least reactive (i) F, Cl, Br(ii) Li, Na, K ........................................ ........................................

Q 35.4 | Page 305

State one reason for keeping fluorine and chlorine in the same of the periodic table.

Q 35.5 | Page 305

What are the merits of the modern periodic table of elements?

Q 36.1 | Page 305

What is a group in the periodic table?

Q 36.2 | Page 305

In which part of a group would you separately expect the elements to have the greatest metallic character

Q 36.3 | Page 305

In which part of a group would you separately expect the elements to have the largest atomic size?

Q 36.4 | Page 305

In what respects do the properties of group 1 elements differ from those of group 17 elements? Explain with examples by taking one element from each group.

Q 36.5 | Page 305

From the standpoint of atomic structure, what determines which element will be the first and which the last in a period the periodic table?

Q 36.6 | Page 305

Explain why, the properties of elements are repeated after 2, 8, 18 and 32 elements in the periodic table.

Q 36.7 | Page 305

What are the advantages of the periodic table?

Q 37 | Page 305

Which of the following statements is not a correct statement about the trends when going from left to right across the periods of periodic Table.

• The elements become less metallic in nature.

• The number of valence electrons increases.

• The atoms lose their electrons more easily.

• The oxides become more acidic.

Q 38 | Page 305

The electronic configuration of the atom of an element X is 2, 8, 4. In modern periodic table, the element is places in :

(a) 2nd group
(b) 4th group
(c) 14th group
(d) 8th group

Q 39 | Page 305

The atomic number of an element is 20. In modern periodic table, this element is placed:

(a) 2nd period
(b) 4th period
(c) 3rd period
(d) 1st period

Q 40 | Page 305

Five elements A, B, C, D and E have atomic numbers of 2, 3, 7, 10 and 18 respectively. The elements which belong to the same period of the periodic table are:

(a) A, B, C
(b) B, C, D
(c) A, D, E
(d) B, D, E

Q 41 | Page 305

The elements A, B, C, D and E have atomic numbers 9, 11, 17, 12 and 13 respectively. The pair of elements which belongs to the same group of the periodic table is:

(a) A and B
(b) B and D
(c) A and C
(d) D and E

Q 42 | Page 305

Which of the following element would lose an electron easily?

(a) Mg
(b) Na
(c) K
(d) Ca

Q 43 | Page 305

Which of the following element does not lose an electron easily?

(a) Na
(b) F
(c) Mg
(d) Al

Q 44 | Page 305

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

Q 45 | Page 305

An element which is an essential constituent of all organic compounds belongs to following group of modern periodic table:

(a) group 4
(b) group 14
(c) group 15
(d) group 16

Q 46 | Page 306

Which of the following is the valence shell for the elements of second period of the modern periodic table?

(a) M shell
(b) K shell
(c) L shell
(d) N shell

Q 47 | Page 305

The element which has the maximum number of valence electrons is:
(a) Na
(b) P
(c) Si
(d) A

Q 48 | Page 306

The correct increasing order of the atomic radii of the elements oxygen, fluorine and nitrogen is:
(a) O, F, N
(b) N, F, O
(c) O, N, F
(d) F, O, N

Q 49 | Page 306

The atomic numbers of the elements Na, Mg, K and Ca are 11, 12, 19 and 20 respectively. The element having the largest atomic radius is:

(a) Mg
(b) Na
(c) K
(d) Ca

Q 50 | Page 306

Which of the following are the correct characteristics of isotopes of an element?
(i) same atomic mass
(ii) same atomic number
(iii) same physical properties
(iv) same chemical properties

(a) (i), (ii) and (iv)
(b) (ii), (iii) and (iv)
(c) (ii) and (iii)
(d) (ii) and (iv)

Q 51 | Page 306

The correct formula of the oxide of Eka-aluminium element predicted by Mendeleev was:

(a) EaO3
(b) Ea3O2
(c) Ea2O3
(d) EaO

Q 52 | Page 306

The element which can from an acidic oxide should be the one whose atomic number is:

(a) 6
(b) 16
(c) 12
(d) 19

Q 53 | Page 306

The element which forms a basis oxide has the atomic number of:

(a) 18
(b) 17
(c) 14
(d) 19

Q 54 | Page 306

Which one of the following does not increase while moving down the group of the periodic table?

(b) metallic character
(c) valence electrons
(d) shells in the atoms

Q 55 | Page 306

On moving from left to right in a period of the periodic table, the atomic number of elements increases. What happens to the size of atoms of elements on moving from left to right in a period?

(a) increases
(b) decreases
(c) remain the same
(d) first increases then decreases

Q 56 | Page 306

Which of the following set of elements is written correctly in the order of their increasing metallic character?

(a) Mg, Al, Si
(b) C, O, N
(c) Na, Li, K
(d) Be, Mg, Ca

Q 57 | Page 306

The atomic numbers of the three elements X, Y and Z are 2, 6 and 10 respectively.
(i) Which two elements belong to the same group?
(ii) Which two elements belong to the same period?

Q 58 | Page 306

An atom has the electron structure of 2, 7.
(a) What is the atomic number of this atom?
(b) To which of the following would it be chemically similar?
7N, 15P, 17Cl, 18Ar
(c) Why would you expect it to be similar?

Q 59 | Page 306

Consider the following elements:
20Ca, 8O, 18Ar, 16S, 4Be, 2He
Which of the above elements would you expect to be:

(i) very stable?
(ii) in group 2 of the periodic table?
(iii) in group 16 of the periodic table?

Q 60.1 | Page 306

In each of the following pair, choose the atom having the bigger size:

(a) Mg (At. No.12) or Cl (At. No.17)

Q 60.2 | Page 306

In each of the following pair, choose the atom having the bigger size:

Na (At. No. 11) or K (At. No. 19)

Q 61 | Page 306

The atomic numbers of three elements A, B and C are given below:

 Element Atomic number A 5 B 7 C 10

(i) Which element belongs to group 18?
(ii) Which element belongs to group 15?
(iii) Which element belongs to group 13?
(iv) To which period/periods do these elements belong?

Q 62 | Page 306

An element X belongs to 3rd period and group 2 of the periodic table. State:

(a) number of valence electrons
(b) valency
(c) metal or non-metal
(d) name of the element

Q 63 | Page 307

The following diagram shows a part of the periodic table in which the elements are arranged according to their atomic numbers. (The letters given here not the chemical symbols of the elements):

 a3 b4 c5 d6 e7 f8 g9 h10 i11 j12 k13 l14 m15 n16 o17 p18

(i) Which element has a bigger atom, a or f?
(ii) Which element has a higher valency, k or o?
(iii) Which element is more metallic i or k?
(iv) Which element is more non-metallic, d or g?
(v) Select a latter which represents a metal of valency 2.
(vi) Select a letter which represents a non-metal of valency 2.

Q 64.1 | Page 307

An element X is in group 2 of the periodic table What will be the formula of its chloride?

Q 64.2 | Page 307

An element X is in group 2 of the periodic table what will be the formula of its oxide?

Q 65 | Page 307

An element Y is in second period and group 16 of the periodic table:

(i) Is it a metal or non-metal?
(ii) What is the number of valence electrons in its atom?
(iii) What is its valency?
(iv) What is the name of the element?
(v) What will be the formula of the compound formed by Y with sodium?

Q 66.1 | Page 307

As element X has mass number 40 and contains 21 neutrons in its atom. To which group of the periodic table does it belong?

Q 66.2 | Page 307

The element X forms a compound X2Y. Suggest an element that Y might be and give reasons for your choice.

Q 67 | Page 307

An element X combines with oxygen to form an oxide XO. This oxide is electrically conducting.

(a) How many electrons would be there in the outermost shell of the element X?
(b) To which group of the periodic tables does the element X belong?
(c) Write the formula of the compound formed when X reacts with chlorine.

Q 68 | Page 307

An element A has an atomic number of 6. Another element B has 17 electrons in its one neutral atom.

(a) In which groups of the periodic table would you expect to find these elements?
(b) what type of bond is formed between A and B?
(c) Suggest a formula of the compound formed between A and B.

Q 69 | Page 307

The elements A, B, C and D belong to groups 1, 2, 14 and 17 respectively of the periodic table. Which of the following pairs of elements would produce a covalent bond?
(i) A and D
(ii) C and D
(iii) A and B
(iv) B and C
(v) A and C

Q 70 | Page 307

An element X from group 2 reacts with element Y from group 16 of the periodic table.
(a) What is the formula of the compound formed?
(b) What is the nature of bond in the compound formed?

Q 71 | Page 307

A metal X is in the first group of the periodic table. What will be the formula of its oxide?

Q 72 | Page 307

An element A from group 14 of the periodic table combines with an element B from group 16.

(i) What type of chemical bond is formed?
(ii) Give the formula of the compound formed.

Q 73 | Page 307

An element X from group 2 of the periodic table reacts with an element Y from group 17 to form a compound.

(a) What is the nature of the compound formed?
(b) State whether the compound formed will conduct electricity or not.
(c) Give the formula of the compound formed.
(d) What is the valency of element X?
(e) How many electrons are there in the outermost shell of an atom of element Y?

Q 74 | Page 308

The following diagram shows a part of the periodic table containing first three periods in which five elements have been represented by the letters a, b, c, d and e (which are not their chemical symbols):

 1 18
 a 2 13 14 15 16 17 b c d e

(i) Select the letter which represents an alkali metal.
(ii) Select the letter which represents a nobles gas.
(iii) Select the letter which represents a halogen.
(iv) What type of bond is formed between a and e?
(v) What type  of bond is formed between d and e?

Q 75 | Page 308

The elements A, B and C belong to groups 1, 14, and 17 respectively of the periodic table.
(a) Which two elements will form a covalent compound?
(b) Which two elements will form an ionic compound?

Q 76 | Page 308

Find the neutral atom in the periodic table which has the same number of electrons as K+ and Cl. What is this number?

Q 77 | Page 308

Atoms of eight elements A, B, C, D, E, F, G and H have the same number of electron shells but different number of electrons in their outermost shells. It was found that elements A and G combine to form an ionic compound. This ionic compound is added in a small amount to almost all vegetables and dishes during cooking. Oxides of elements A and B are basis in nature while those of elements E and F acidic. The oxide of element D is, however, almost neutral. Based on the above information, answer the following questions:

(a) To which group or period of the periodic table do these elements belong?
(b) What would be the nature of compound formed by a combination of elements B and F?
(c) Which two of these elements could definitely be metals?
(d) Which one of the eight elements is most likely to be found in gaseous state at room temperature?
(e) If the number of electrons in the outermost shell of elements C and G be 3 and 7 respectively, write formula of the compound formed by the combination of C and G.

Q 78 | Page 308

Write the names and symbols of two very reactive metals belonging to group 1 of the periodic table. Explain by drawing electronic structure, how either one of the two metals reacts with a halogen. With which name is the bond formed between these elements known and what is the class of the compound so formed known? State any four physical properties of such compounds.

Q 79 | Page 308

The non-metal A is an important constituent of our food and most of the fuels around us. A forms two oxides B and C. The oxide B is poisonous whereas oxide C causes global warming.

(a) Identify A, B and C.
(b) To which group of periodic table does A belong?
(c) Name another element which is placed in the  same group as A.

Q 80 | Page 308

A non-metal X which is the largest constituent of air combines with hydrogen when heated in the presence of iron as catalyst to form a gas Y. When gas Y is treated with sulphuric acid, it forms a compound Z which is used as a chemical fertiliser.

(a) What are X, Y and Z?
(b) To which group of periodic table does X belong?
(c) Name the periodic table in which X is placed.
(d) Which element is placed just before X in the period?
(e) Which element is placed just after X in the period?

## Lakhmir Singh solutions for Class 10 Science chapter 5 - Periodic Classification Of Elements

Lakhmir Singh solutions for Class 10 Science chapter 5 (Periodic Classification Of Elements) include all questions with solution and detail explanation. This will clear students doubts about any question and improve application skills while preparing for board exams. The detailed, step-by-step solutions will help you understand the concepts better and clear your confusions, if any. Shaalaa.com has the CBSE Chemistry for Class 10 (2019 Exam) solutions in a manner that help students grasp basic concepts better and faster.

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Concepts covered in Class 10 Science chapter 5 Periodic Classification Of Elements are Position of Elements and Trends in the Modern Periodic Table, The Modern Periodic Table, Limitations of Mendeleev’s Classification, Achievements of Mendeleev’s Periodic Table, Mendeleev’s Periodic Table, Early Attempts at the Classification of Elements - Newlands’ Law of Octaves, Early Attempts at the Classification of Elements - Dobereiner’s Triads, Periodic Classification of Elements Questions, Periodic Classification of Elements Introduction.

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