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Chapter 5 of NCERT Solutions for Class 10 Science – Summary:
- Elements are classed according to how comparable their properties are.
- Newlands devised the Law of Octaves after Döbereiner divided the elements into triads.
- The elements were organized by Mendeleev in ascending order of their atomic weights and chemical characteristics.
- On the basis of gaps in his Periodic Table, Mendeleev even anticipated the existence of several yet-to-be-discovered elements.
- When the elements were organized in order of increasing atomic number, a fundamental attribute of the element identified by Moseley, anomalies in the arrangement of elements based on rising atomic mass could be addressed.
- The Modern Periodic Table divides elements into 18 vertical columns called groups and seven horizontal rows named periods.
- The periodicity of features such as atomic size, valency or combining capacity, and metallic and non-metallic character can be seen in this arrangement.
Ncert textual questions
1. 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.
i) The elements become less metallic in nature
ii) The number of valence electrons increases
iii) The atoms lose their electrons more easily
iv) The oxides become more acidic
A. iii) The atoms lose their valence electrons with difficulty and not easily. This is on account of the reason that.
Nuclear charge increases from left to the right.
Since the atomic number of the elements gradually increases.
With the increase in nuclear charge, the force binding the electrons with the nucleus increases. Therefore the atoms lose their valence electrons with difficulty.
2. Element ‘X’ forms a chloride with the formula XCl2which is a solid with high melting point. ‘X’ would most likely to be in the same group of the
i) Na ii) Mg iii) Al iv) Si
A. ii) The formula of the chloride of the element is XCl2. This means that the valency of the element X is 2 since chlorine is monovalent. The element with valency 2 is expected to be present in group 2 so which Magnesium (Mg) belongs.
3. Which element has
i) Two shells, both of which are completely filled with electrons ?
ii) The electronic configuration 2, 8, 2 ?
iii) A total of three shells with four electrons in the valence shell ?
iv) A total of two shells with three electrons in the valence shell ?
v) Twice as many electrons in the second shell as in the first shell ?
A. i) The elements with completely filled shells are noble gas elements and they belong to group 18. Since the element has two shells; it must be present in second period and is Neon (Ne) with electronic configuration 2, 8.
ii) The electronic configuration suggests that the element belongs to thrid period and second group. It is therefore, Magnesium (Mg).
iii) The element with three shells is present in third period. Since it has four electrons in the valence shell, it must belong to group 14 and is Silicon (Si) with electronic configuration 2, 8, 4.
iv) The element with two shells is expected to be present in the second period. With three electrons in the valence shell, it must belong to group 13 and is Boron (B) with electronic configuration 2, 3.
v) The element has only two shells. The first shell can have maximum of two electrons. The second shell has four electrons which is twice the number of electrons present in the first shell. Therefore the electronic configuration of element is 2, 4. It is carbon with atomic number (Z) equal to 6.
4. i) Which property do all elements in the same column of the periodic table as boron have in common?
ii) Which property do all elements in the same column of the periodic table as fluorine have in common?
A. i) The element Boron (B) is the first member of group (also called column) 13. it has three electrons in the valence shell (2, 3). The other elements included in the same column are Aluminium (Al), Gallium (Ga), Indium (In) and Thalium (Tl). They too have three electrons in the valence shell of their atoms. Just like Boron, these elements also show a valency of 3 in their compounds.
ii) The element Fluorine (F) is the first member of group (also called column) 17. It has seven electrons in the valence shell (2, 7). The other members present in the same group known as halogen family are Chlorine (Cl), Bromine (Br). Iodine (I) and Astatine (At). They have also seven electrons in the valence shell of their atoms like fluorine, they all show a valency of 1in their compounds.
5. An atom has electronic configuration 2, 8, 7
i) What is the atomic number of this element?
ii) To which of the following elements would it be chemically similar? (Atomic numbers are given in parentheses). N(7), F(9), P(15), Ar(18)
A. i) The atomic number of the element is 17. (2 + 8 + 7 = 17)
ii) It would be chemically similar with Fluorine (F) which has also 7 electrons in valence shell
(2, 7)
6. The position of three elements A, B and C in the Periodic Table are shown below –
| Group 16 | Group 17 |
| – | – |
| – | A |
| – | – |
| B | C |
a) State whether A is a metal or non-metal.
b) State whether C is more reactive or less reactive than A.
c) Will C be larger or smaller in size than B?
d) Which type of ion, cation or anion, will be formed by element A?
A.
a) A is a nonmetal
b) C is less reactive than A
c) C is smaller than B
d) Anion
7. Nitrogen (atomic number 7) and Phosphorus (atomic number 15) belong to group 15 of the periodic table, write their electronic configuration. Which of these will be more electronegative and why?
A. The electronic configuration of the two elements are Nitrogen (z = 7) 2, 5; Phosphorus (z = 15)
2, 8, 5. Since the size of the nitrogen is small as compared to phosphorus, it has a greater tendency to take up electrons it is therefore, more electro negative than phosphorus.
8. How does the electronic configuration of an atom relate to its position in the modern periodic table?
A. The modern periodic table is based upon atomic numbers of the elements. Since electronic configurations of the elements depend upon their atomic numbers, this means that the periodic table is based on the electronic configurations of the elements. For example, all the alkali metals have one electron each in their valence shell. These are placed in group 1. Similarly, the alkaline earth metals with two electrons in their valence shell are placed in group 2 and so on.
9. In the modern periodic table, Calcium (Z = 20) is surrounded by the elements with atomic numbers 12, 19, 21 and 38. Which of these have physical and chemical properties resembling Calcium?
A. Only those elements are placed in the same group in which the gaps of atomic numbers are : 2, 8, 8, 18, 18, 32. If we look at the atomic numbers of the elements that are listed, it becomes clear that the elements with atomic numbers 12, 20 (Ca), 38 fit into this pattern. They are placed in the same group and have also similar physical and chemical properties.
10. Compare and contrast the arrangement of elements in Mendeleev’s periodic table and the modern periodic table.
A. The main points of distinction between Mendeleev’s periodic table and modern periodic table are as follows :
Mendeleev’s Periodic Table Modern Periodic Table
1) It regards atomic masses of the elements 1) It regards atomic number of the elements as
as the basis of classification the basis of classification
2) No separate positions or slots have been 2) There is no need for the separate slots for the
allotted to the isotopes of an elements isotopes since they have the same atomic
since they have different atomic masses numbers
3) No justification is made for placing 3) Justification has been made for placing
hydrogen in group IA along with alkali hydrogen along with alkali metals in group
metals 1 since both hydrogen and alkali metals have
one valence electron
4) Except for the elements in group VIII, the 4) There are no sub-groups and all groups are
remaining groups have been divided with independent in nature.
sub-groups A and B
5) Position of certain elements based on their 5) Modern periodic table is free from such
atomic masses misfits, for example the anomalies the element cobalt is placed before
element cobalt (atomic mass 58.9) has nickel since its atomic number (27) is less than
been placed on a head of nickel that nickel (28)
(atomic mass = 58.7)
6) Electronic configurations and properties 6) Both electronic configuration and certain
of the elements cannot be predicted from properties of the elements can be predicted
their positions in the table. from their positions in the periodic table.
7) It is not very systematic and is difficult to 7) It is quite systematic and is easy to remember.
remember
NCERT TEXTUAL EXCERCISES
1. Did Dobereiner’s triads also exist in the columns of Newland’s octaves? Compare and find out?
A. Yes, some of the Dobereiner’s triads did exist in the columns of Newlands Octaves. For example
Li, Na, K Be, Mg, Ca
(triad) (triad)
2. What were the limitations of Dobereiner’s classification?
A. Dobereiner was in a position to identify three triads. It could not apply to all the elements known at that time therefore, the classification was not so useful.
3. What were the limitations of Newlands law of octaves?
A. The major limitations of Newland’s law of octaves are :
i) It is applicable to only lighter elements having atomic masses up to 40U, i.e., up to Calcium. After Calcium, the first and the eight elements do not have similar properties. For example Chromium (Cr) and yttrium (Y) are the first and the eight element placed in the same column but have entirely different properties.
ii) Some similar elements have been separated from one another while some dissimilar elements have been placed in the same column. For example, Iron (Fe) resembles Cobalt (Co) and Nickel (Ni) but has been placed far away from these elements.
4. Use Mendeleev’s periodic table to predict the formulae for the oxides of the elements: K, C, Al, Si, Ba.
A. Oxygen is a member of group VIA in Mendeleev’s periodic table. Its valency is 2. Similarly, the valences of all the elements listed can be predicted from their respective groups. This can help in writing the formulae of their oxides.
i) Potassium (K) is a member of group IA. Its valency is 1. Therefore, the formula of its oxide is K2
ii) Carbon (C) is a member of group IVA. Its valency is 4. Therefore the formula of its oxides is CO2.
iii) Aluminium (Al) belongs to groups IIIA and its valency is 3. The formula of the oxides of the element is Al2O3.
iv) Silicon (Si) is present in group IVA after Carbon. Its valency is also 4. The formula of its oxide is Si2O4 or SiO2.
v) Barium (Ba) belongs to group IIA and the valency of the element is 2. The formula of the oxide of the element is Ba2O2 (or) BaO.
5. Besides Gallium which two other elements have since been discovered that fill the groups left by Mendeleev in creating his periodic table?
A. Two other elements are Scandium (Sc) and Germanium (Ge). In their gaps, the elements with names
Eka – Boron and Eka – Silicon were placed.
6. What was the criteria used by Mendeleev in creating his periodic table?
A. The atomic masses of the elements were used as criteria in creating Mendeleev’s periodic table.
7. Why do you think that the noble gases should be placed in a separate group?
A. In the Mendeleev’s periodic table, the elements have been arranged in the different groups on the basis of valency. For example, the elements in group I (IA and IB) have valency equal to one. Some in the case with the elements placed in other groups. Since the noble gas elements He, Ne, Ar, Kr, Xe and Rn have zero valency, they could not find a place in a separate group called Zero group in the periodic table. Please note that the noble gas elements were not a part of the Mendeleev’s periodic table. They were added later on.
8. How could the modern table remove various anomalies of Mendeleev’s periodic table ?
A. i) In the modern periodic table, the elements are arranged in order of their increasing atomic numbers. Since, the atomic number of Co is 27 and that of Ni is 28, therefore Cobalt is placed before Nickel and hence, their positions are justified in the modern periodic table. Thus the defect of anomalous pair in Mendeleev’s periodic table is removed.
ii) In the modern periodic table, elements are arranged in increasing order of their atomic numbers. Since the various isotopes of an element have the same atomic number, therefore they are assigned the same position in the modern periodic table. Thus, the defect of position of isotopes in Mendeleev’s periodic table is eliminated.
9. Name two elements you would expect to show chemical reactions similar to Magnesium. What is the basis for your choice?
A. Magnesium (Mg) belongs to group 2 known as Alkaline earth metals family. The two other elements belonging to the same group are Calcium (Ca) and Strontium (Sr). The basis of choice is the electronic distribution in the valence shell of these elements. All of them have two electrons each. For example
| K | L | M | N | O | |
| Mg (Z = 12) | 2 | 8 | 2 | – | – |
| Ca (Z = 20) | 2 | 8 | 8 | 2 | – |
| Sr (Z = 38) | 2 | 8 | 18 | 8 | 2 |
10. Name:
i) Three elements that have a single electrons in their outermost shells.
ii) Three elements that have two electrons in their outermost shells.
iii) Three elements with filled outer most shells.
A. i) Lithium, Sodium, Potassium (Alkali metals)
ii) Beryllium, Magnesium, Calcium (Alkaline earth metals)
iii) Helium, Neon, Argon (Noble gases)
11. i) Lithium, Sodium, Potassium are all metals that react with water to liberate hydrogen gas. is there any similarity in the atoms of these elements?
ii) Helium is an unreactive gas and neon is a gas of extremely low reactivity. What if anything, do their atoms have in common.
A. i) Lithium, Sodium and Potassium all react with water to form alkali’s i.e., Lithium hydroxide, Sodium hydroxide, Potassium hydroxide etc. with the liberation of Hydrogen gas.
| 2Li
lithium |
+ | 2H2O
water |
2LiOH
lithium hydroxide |
+ | H2
hydrogen |
|
| 2Na
sodium |
+ | 2H2O
water |
2NaOH
sodium hydroxide |
+ | H2
hydrogen |
|
| 2K
potassium |
+ | 2H2O
water |
2KOH
potassium hydroxide |
+ | H2
hydrogen |
All these metals have one electron in their respective outermost shells.
ii) Helium and Neon are noble gases and hence have extremely low chemical reactivity. They have their shells completely filled. Helium has only K shell which is complete, i.e has 2 electrons.
Neon, on the other hand, have two shells, K and L. Both these shells are complete i.e. K shell has 2 electrons and L-shell has 8 electrons.
12. In the modern periodic table, which are the metals among the first ten elements?
A. Metals among the first ten elements are Lithium (Li) and Beryllium (Be). These are placed towards the left of the table.
13. By considering their position in the periodic table, which one of the following elements would you expect to have the most metallic characteristics? Ga, Ge, As, Se, Be?
A. Arranging the given elements in different groups and periods in order of their increasing atomic numbers. We have
| Periods | Group – 1 | Group – 2 | Group – 3 | Group – 4 | Group – 5 | Group – 6 |
| 1 | – | – | – | – | – | – |
| 2 | – | Be | – | – | – | – |
| 3 | – | – | – | – | – | – |
| 4 | – | – | Ga | Ge | As | Se |
We know that metallic character decreases from left to right in a period and increases down a group. Therefore, out of the elements listed in the question. Be and Ga are expected to be most metallic. Out of Be and Ga, Ga is bigger in size and hence has greater tendency to lose electrons than Be. Therefore, Ga is more metallic than Be.
NCERT Exemplar Solutions for Science Chapter 5 in Class 10 are also available.
Class 10 Science Chapter 5 CBSE Notes
NCERT Solutions for Class 10 Science Chapter 5: Periodic Classification of Elements
Unit Chemical Substances – Nature and Behaviour are covered in NCERT Class 10 Science Chapter 5- Periodic Classification of Elements. Because this unit accounts for the highest marks in the board exam of any chapter in the syllabus, all chapters in Unit Chemical Substances must be extensively studied. The periodic categorization of elements chapter alone earns 5 points in the CBSE Term II test, as predicted by a thorough examination of prior question papers.
Subtopics discussed in Chapter 5 – Periodic Classification of Elements include the following:
5.1 Creating Order from Chaos – Early Attempts at Elements Classification
We’ve been learning about how different things or live beings can be classed based on their characteristics. We come across organizations based on some features in a variety of scenarios. The concept of Döbereiner Triads and Newlands’ Law of Octaves are discussed in this topic. Both notions are shown with appropriate instances.
5.2 Mendeleev’s Periodic Table: Creating Order Out of Chaos
Mendeleev’s Periodic Table, Achievements of Mendeleev’s Periodic Table, and Mendeleev’s Classification Limitations are all covered in this topic. The periodic table, as well as Dmitri Ivanovich Mendeleev’s development of the periodic table, are discussed.
5.3 The Modern Periodic Table: Bringing Order to Chaos
Properties of elements are a periodic function of their atomic number, according to the Modern Periodic Table. The article goes on to address the Modern Periodic Table’s Position of Elements, as well as trends in the Modern Periodic Table such as valency, Atomic Size, Metallic and Non-metallic Properties.
Exercises with questions on the list
5.1 – Creating order in the midst of turmoil 3 Inquiry (2 long, 1 short)
-The first attempts at classifying elements
5.2 – Creating order in the midst of chaos
– Periodic Table 4 Question by Mendeleev (1 long, 3 short)
5.3 – Creating order in the midst of turmoil
-Question 6 from the Modern Periodic Table (1 long, 5 short)
10 Question Exercise Solutions (2 long, 8 short)
NCERT Solutions for Class 10 Science Chapter 5 – Periodic Classification of Elements
The Periodic Classification of Elements provides a basic overview of how elements are classed based on similarities in their shared properties. It briefly covers Döbereiner classification of various elements into triads, as well as Newland’s suggested Law of Octaves. The chapter briefly examines Mendeleev’s suggestion that elements be arranged in ascending order of their atomic numbers and chemical properties, as he projected the existence and presence of some yet-to-be-discovered elements due to gaps in the Periodic table.
The limitations of Mendeleev’s classification, and thus the present periodic table, are also discussed in this chapter. It depicts the vertical and horizontal arrangement of elements in modern periodic elements, as well as the vertical and horizontal arrangement known as groups and periods.
NCERT Answers for 10th class Science Chapter five – Periodic Classification of Elements – Key Features
- NCERT Class 10 Science Solutions are based on a chapter-by-chapter allocation of marks and question type that follows the CBSE design.
- Students will be able to better understand the solutions because they have been developed.
- Numerical problems have been solved with step-by-step instructions.
- Wherever possible, tabular columns have been employed, allowing pupils to learn more quickly.
- The chapter’s wording is straightforward and reasonable.
NCERT Solutions for Class 10 Science Chapter 5: Frequently Asked Questions
What are the ideas covered in NCERT Solutions for Class 10 Science Chapter 5?
The following are the concepts covered in Chapter 5 of NCERT Solutions for Class 10 Science:
5.1 Creating Order from Chaos – Early Attempts at Elements Classification
5.2 Mendeleev’s Periodic Table: Creating Order Out of Chaos
5.3 The Modern Periodic Table: Bringing Order to Chaos
Explain the concept of Mendeleev’s Periodic Table from NCERT Solutions for Class 10 Science, Chapter 5.
In this chapter, the theme of Mendeleev’s Periodic Table is –
- The elements are organized according to their atomic masses in ascending order.
- There are a total of eight groups.
- Each group is broken into ‘a’ and ‘b’ subgroups.
- Noble gases had not yet been discovered at the time, hence the groups for noble gases were missing.
- Isotopes have no place in this world.
Why should I use the NCERT Solutions for Science Chapter 5 in Class 10?
- The NCERT Solutions are generated using the CBSE blueprint’s chapter-by-chapter mark distribution.
- Students might have a better understanding of concepts by using elaborate answers.
- For the numerical in this chapter, step-by-step explanations are provided.
- Students’ morale is enhanced by the use of simple and reasonable language.
- Wherever possible, pupils are given visual representations to help them absorb subjects more quickly.
