# NIOS Class 10 Science & Technology Chapter 6 Solution

## NIOS Class 10 Science & Technology Chapter 6 Solution – Periodic Classification Of Elements

NIOS Class 10 Science & Technology Solution Chapter 6 Periodic Classification Of Elements. NIOS Class 10 Science & Technology Chapter 6 Question Answers Download PDF. NIOS Class 10 Science Notes.

### NIOS Class 10 Science & Technology Chapter 6 Solution

 Board NIOS Class 10th  (Secondary) Subject Science and Technology (212) Topic Question Answer, Solution, Notes

CHAPTER: – 6

(PERIODIC CLASSIFICATION OF ELEMENTS)

INTEXT QUESTIONS 6.1

1) Elements A, B and C constitute a Dobereiner’s triad. The atomic mass of A is20 and that of C is 40. Predict the atomic mass of B.

Ans: – According to Doberniar trad formula the mass of the middle element will be average of the remaining two’s sum. So, the atomic mass of B will be (20 +40)/2 =30.

2) Which property of atoms was used by Mendeleev to classify the elements?

Ans: – Mendeleev classify the atom according to their atomic masses.

3) In Mendeleev’s periodic classification, whether chemically similar elements are placed in a group or in a period?

Ans: – In Mendeleev periodic table the chemically similar elements are placed in a group.

4)Mendeleev’s periodic table had some blank spaces. What did they signify?

Ans: – This signify that in future this will be discovered by someone with the same characteristics.

5) Explain any three defects of Mendeleev’s periodic table.

Ans: – The three defect are: –

• (i)Hydrogen position.
• (ii) isotopes present in different position.
• (iii)separation of similar element to different places.

INTEXT QUESTIONS 6.2

1) Give any two defects of Mendeleev’s periodic table which has been removed in modern periodic table. How were they removed ?

Ans: – The element is kept according to their atomic number in the modern periodic table as in previous table there is seen a problem that similar property showing elements are kept in other positions which rearrange accordingly.

2) Metalloids are present along the diagonal line starting from group 13 and going down to group 16. Do they justify their position in the modern periodic table?

Ans: – As isotopes of an element must be same atomic number then all will occupy the same position in the periodic table as a result of that we see the metalloid ae present along the diagonal line in the periodic table.

INTEXT QUESTIONS 6.3

1) Fill in the blanks with appropriate words

(a) The force of attraction between nucleus and valence electrons …. increase………….in a period from left to right.

(b) Atomic radii of elements ……. decrease………. in a period from left to right.

(c) Atomic radii of elements ……. increase………. in a group from top to bottom.

(d) Metallic character of elements …. increase………… from top to bottom in a group.

2) In the following crossword puzzle, elements are present horizontally, vertically downwards and diagonally downwards. Let us find out how many elements you are able to get within 5 minutes.

Ans: –

Horizontally: – H, C, Ba, Na, B,Cl.

Vertically: – Mg,I,He,Ne,Si.

Diagonally: – N,O.

3) Let us find how many riddles you can solve.

(i) I am the only noble gas whose outermost shell has 2 electrons. Who amI?

(ii) I am placed in group 16 of the modern periodic table and essential for your respiration. Who am I?

(iii)I combine with chlorine to form your table salt. Who am I?

Ans: – (i) So it will be helium.

(ii)It must be oxygen.

(iii)Sodium combined with the table salt.

TERMINAL EXERCISE

A. Objective questions

I. Mark the correct choice:

1) Which one of the following was the earliest attempt of classification of elements?

• (a) Classification of elements into metals and non-metals
• (b) Newlands’ Law of Octaves.
• (c) Dobereiner’s Triads
• (d) Mendeleef’s Periodic Table.

Ans: – Option (d).

2) The ‘law of octaves’ was given by

• (a) Mendeleev
• (b) Newlands
• (c) Lother Meyer
• (d) Dobereiner.

Ans: – option (b).

3) According to the periodic law given by Mendeleev, the properties of anelement are a periodic function of its

• (i) atomic volume
• (ii) atomic size
• (iii) atomic number
• (iv) atomic mass.

Ans: – Option (iv).

4) The particle which is universally present in the nuclei of all elements is

• (a) neutron
• (b) proton
• (c) electron
• (d) α-particle.

Ans: – Option (b).

5) Potassium is more metallic than sodium because

• (a) both have 1 electron in their outermost shell.
• (b) both are highly electropositive.
• (c) sodium is larger in size than potassium.
• (d) potassium is larger in size than sodium.

Ans: – Option (c).

7) Which one of the following elements in its chloride does not show the valenceequal to its valence electrons ?

• (a) NaCl
• (b) MgCl2
• (c) AlCl3
• (d) PCl3.

Ans: – Option (d).

8) Which one of the following elements has the least tendency to form cation?

• (a) Na
• (b) Ca
• (c) B
• (d) Al.

Ans: – Option (c).

9)Which one of the following does not belong to the family of the alkali metals?

• (a) Li
• (b) Na
• (c) Be
• (d) K.

Ans: – Option(c).

10) The number of elements in the 5th period of the periodic table is

• (a) 2
• (b) 8
• (c) 32
• (d) 18.

Ans: – Option (c).

11) The elements with atomic number 9 resembles with the element having atomic number

• (a) 35
• (b) 27
• (c) 17
• (d) 8.

Ans: – Option (c).

12) In which period of the periodic table, an element with atomic number 20 is placed?

(a) 4

(b) 3

(c) 2

(d) 1.

Ans: – Option (a).

II. Mark the following statements True (T) or False (F) :

1) The properties of the middle element in a Dobereiner’s triads are intermediate between those of the other two. (True)

2) The vertical columns in the periodic table are called periods. (False)

3) Mendeleev depended only on the atomic mass of elements for his classification. (True)

4) All elements present in a group are chemically similar. (True)

5) The modern periodic law is based upon atomic mass. (False)

6) The importance of atomic number as the fundamental property was realized by Henry Mosely. (True)

7) There are 18 groups in the modern periodic table. (True)

8) Non-metals are present in the middle portion of the periodic table. (True)

9) Each period in modern periodic classification begins with filling of electrons in a new shell. (True).

III. Fill in the blanks:

1. According to the modern periodic law, the properties of elements are periodicfunction of their ……… atomic number…………

2. The ……. group………….. number is same as the number of shells which in gradually filled up in the elements of this period.

3. In normal elements of a particular period the electrons are gradually filled in……..lower…………. shell.

4. All elements of a particular group have ……..same…………. electronic configurations.

5. In the modern periodic table, groups are numbered from ………1………… to…….18…………..

6. The second and third periods of the periodic table are called ……..short………….periods.

7. The main group elements are present in group 1 and 2 on the left side and………17………… to …..18……………. on the right side of the periodic table.

8. All the group eighteen elements (except the first one) contain ……..0………….valence electrons.

9. All transition elements are metals with ……..high…………. melting and boiling points.

10. The group of 14 rare-earth elements belonging to the group 3 and 7th periodare called …………………

11. All elements present in a given ……… group………… have the same valency.

12. Atomic size ……… decrease………… in a period from left to right.

13. Magnesium is ……..less…………. metallic than calcium.

14. Carbon belongs to group ………14……….. of the Periodic table.

15. All the elements of group 15 have ….3…………….. valence electrons.

B. Subjective Questions

I. Very short Answer Questions (Answer in one word or one sentence).

1)What was the earliest classification of elements?

Ans: – The earliest classification of elements is according to their atomic masses.

2) State Newlands’ law of octaves.

Ans: – The Newland law states the eight elements subsequently shows same property.

3) Which classification of elements failed after the discovery of noble gases ?

Ans: – Mendeleev classification failed after the discovery of noble gases.

4) State Mendeleev’s Periodic Law.

Ans: – Mendeleev period law states that the elements are kept in the periodic table according to their atomic masses.

5) How were the groups numbered in the Mendeleev’s periodic table?

Ans: – There are 8 group in Mendeleev periodic table.

6) Name the fundamental properties of element on which the modern periodic law is based.

Ans: – Atomic number.

7) How many groups are there in the modern periodic table?

Ans: – There are 18 group in modern periodic table.

8) How have groups been numbered in the modern periodic table?

Ans: – 18 group been number in modern periodic table.

9) What are normal elements ?

Ans: – In group 1, 2 and from 13 to 17 are normal element.

10) What are the elements present in the middle portion of the modern periodic table called?

Ans: – Transitions elements.

11)What is atomic size?

Ans: – The size of elements including its shell.

12) How does atomic size vary in a period and in a group?

Ans: – Atomic size increasing down a group and decrease from left to right a period.

13) Where would the element with largest atomic size be placed in any group?

Ans: – At the lowest point under a group.

14) Give the number of a group in which metallic, metalloid and non-metallic, all three types of elements, are present.

Ans: – Group 14.

II. Short Answer Questions (Answer in 30-40 words).

1) State Dobereiner’s law of triads.

Ans: – The Dobereiner’s triad laws state that the middle element of three consecutive elements has the masse of the average of the remaining first and the third elements. This all three then formed triad and shows the similar properties.

2) Show that chlorine, bromine and iodine (atomic masses 35·5, 80 and 127 respectively) constitute a triad.

Ans: – The mass of Bromine is =(35.5 + 127/2)=81.25.

So, here we clearly see that this three-element chlorine, bromine, and iodine shows the similar properties and form triad.

3)What were the reasons for the failure of Newlands’ law of octaves?

Ans: – Newland octave law states that eight consecutive elements in a periodic table shows the similar characteristics but some times it fails to explain the condition where we see that although the atomic number are same this has no similar properties.

4)Describe Mendeleev’s periodic table briefly in terms of rows and columns and their raw being.

Ans: – The Mendeleev periodic table has arranged the different element according to their atomic masses. In this table the all the elements are arrange in 7 period and 8 group.

5) Give any two achievements of the Mendeleev’s Periodic classification.

Ans: – The Mendeleev periodic table is the first table to describe the different element according to their chemical and physical properties. This was the primary idea for keeping the different elements in its places and obeying this table modern periodic table came.

6) What were the defects in Mendeleev’s periodic classification.

Ans: – Although the Mendeleev periodic table described about the different elements it has some defect like it doesn’t explain about the position of hydrogen and keep the different characteristics showing element in same place.

7)State modern periodic law.

Ans: – The modern periodic law the different element is arranged according to their atomic number. This atomic number are increasing from the lower to higher. In a modern periodic table, there are 7 periods and 18 group.

8) Briefly describe the modern periodic table in term of groups and period.

Ans: – In a modern periodic table we see the elements are arranged to its atomic number and the number if group and period in the modern periodic table is 18 and 7.

9) Give names of four classes into which the elements have been classified and mention to which groups of the modern period table they belong.

Ans: – The element in the modern periodic table is differentiate into –

• Metals and non metals.
• Alkaline and alkaline earth metal.
• Transition element.
• F block elements.

10) List the merits of the long form of the modern periodic table and explain any two of them.

Ans: – The merits of modern periodic table are –

• It explains the difference properties according to the increasing atomic number.
• It clearly tells us about the position of hydrogen.

11)How are the electronic configurations of all the elements belonging to a particular group related? Explain with the help of group 17 elements.

Ans: – The group 17 element in a periodic table is known as the halogen element. This element is fluorine, chlorine, bromine, iodine etc.

12) How does the electronic configuration of elements belonging to a particular period vary? Explain with the example of second period elements.

Ans: – The electronic configuration of an element described about the different position of different element. For example, the electronic configuration of element Carbon (2,4) tells us about it position in table and group and periods number.

13) Define atomic radius.

Ans: – The atomic radius of element is depending on the group and period as the radius is increasing from going downward to the group whereas if decreasing from left to right of a period.

14) How and why does metallic character vary in a group from top to bottom?
Ans: – The metallic character of an element is dependent on the loosing of the las electron in the valance shell which increasing from left to right in a period and decreasing from up to down a group.

III. Long Answer Questions (Answer in 60–70 words).

1)State Mendeleev’s Periodic Law and describe the periodic table constructed on this basis.

Ans: – The Mendeleev periodic table has arranged the different element according to their atomic masses. In this table the all the elements are arrange in 7 period and 8 group. There are although some failure in this periodic law which clear in the modern law.

2) What are the merits and demerits of the Mendeleev’s Periodic classification?

Ans: – This was the primary idea for keeping the different elements in its places and obeying this table modern periodic table came. It has some defect like it doesn’t explain about the position of hydrogen and keep the different characteristics showing element in same place.

3)Describe the modern periodic table in terms of groups and periods.

Ans: -In a modern periodic table we see the elements are arranged to its atomic number and the number if group and period in the modern periodic table is 18 and 7. In the modern periodic table we kept the inert gas element in the group 18.

4) What are the following types of elements and where are they located in the periodic table?

• (a) Main group elements
• (b) Noble gases
• (c) Transition elements
• (d) Inner transition elements.

Ans: – The main element of the modern periodic table is kept in the right side of the table. The Nobel gas element are kept in the group 18 of the modern periodic table which is called zero group. The transition element is kept in the middle of the modern periodic table. This element is called the d block elements.

5)Discuss the merits of the modern periodic table.

Ans: – The merits of modern periodic table are –

• It explains the difference properties according to the increasing atomic number.
•  It clearly tells us about the position of hydrogen.

6) What is the relationship between the electronic configuration and the modern periodic table?

Ans: – The electronic configuration of an element described about the different position of different element. For example, the electronic configuration of element sodium (2,8,1) tells us about it position in table and group and periods number.

7) Explain the variation of atomic size in a group and in a period.

Ans: – The atomic radius of element is depending on the group and period as the radius is increasing from going downward to the group whereas if decreasing from left to right of a period. As a result of that we see magnesium has more size than phosphorus.

8) How is metallic character related to ionization energy? Explain the variationof metallic character in the periodic table.

Ans: – The metallic character of an element is dependent on the loosing of the las electron in the valance shell which increasing from left to right in a period and decreasing from up to down a group. As a result of this property, we see that potassium has more metallic character than the sodium.

Updated: February 21, 2022 — 11:47 am