# NCERT Solutions for Class 10 Science Chapter 5 Periodic Classification of Elements

NCERT solutions for class 10 science chapter 5 Periodic Classification of Elements: If you are studying in class 10 and while going through this chapter 5 you face any difficulty or you are not able to understand the concepts or questions related to the chapter, then you don't need to worry. With the help of NCERT solutions for class 10 science chapter 5 Periodic Classification of Elements, you will get all the solutions that are related to the periodic table and classification of the elements. As we know, elements are classified on the basis of similarities in their properties and 118 elements are known to us. Solutions for NCERT class 10 science chapter 5 Periodic Classification of Elements also help you to understand the solutions related to the elements in the Modern Periodic Table. They are arranged in 18 vertical columns called groups and 7 horizontal rows called periods.

The CBSE NCERT solutions for class 10 science chapter 5 Periodic Classification of Elements are solved by the experts as per CBSE( NCERT textbook) guidelines. It includes solutions for the exercise questions mentioned at the end of the chapter and topic wise questions mentioned in between the chapter. NCERT solutions will help you revise the syllabus and score more marks in exams.

Here are the important Topics of NCERT Class 10 Science Chapter 5 Periodic Classification of Elements mentioned below:

5.1 Making Order Out of Chaos - Early attempts in the Classification of Elements

5.1.2 Newland's Law of Octaves

5.2 Making Order Out of Chaos - Mendeleev's Periodic Table

5.2.1 Achievements of Mendeleev's Periodic Table

5.2.2 Limitations of Mendeleev's Classification

5.3  Making Order Out of Chaos - The Modern Periodic Table

5.3.1 The Position of Elements in the Modern Periodic Table

5.3.2 Trends in the Modern Periodic Table

After going through the NCERT solutions for class 10 science, you should be able to get the NCERT solutions of these questions which are mentioned below:

## NCERT solutions for class 10 science chapter 5 Periodic Classification of Elements

Topic 5.1 Making order out of chaos - Early attempts at the classification of elements

Yes, Dobereiner's triads also exist in the column of Newland's octaves.

Newland's law of octaves, says that every eight elements had properties similar to that of the first.

For example, the element Lithium, sodium, and potassium are present in the second column of Newland's classification of elements. If lithium is the first element then, the sodium will be the 8th element and considering again sodium as the 1st element, then the 8th element will be potassium.

So, that means according to Newland's Law of octaves, lithium, sodium, and potassium should have similar properties and also these elements form a Dobereiner's traid having similar chemical properties.

The limitation of Doberenier's classification:

Döbereiner could identify only three triads from the elements known at that time. Hence, this system of classification into triads was not found to be useful.

The limitations of Newland's law of octaves are:

(1) It was found that the Law of Octaves was applicable only up to calcium, as after calcium every eighth element did not possess properties similar to that of the first.

(2) It was assumed by Newlands that only 56 elements existed in nature and no more elements would be discovered in the future. But, later on, several new elements were discovered, whose properties did not fit into the Law of Octaves.

(3) Newland put two elements together in one slot and that too in the column of unlike elements having different properties.

Example: Cobalt and Nickel were put together in just one slot and that too in the column of elements like fluorine, chlorine, and bromine which were very different properties from these elements.

## CBSE NCERT solutions for class 10 science chapter 5 Periodic Classification of Elements

Topic 5.2 Making order out of chaos: Mendeléev’s Periodic Table

The general formula for the oxides of the element Potassium (K): Potassium belongs to the group I of Mendeleev's periodic table, Hence, the formula of its oxide will be $K_{2}O.$

The general formula for the oxides of the element Carbon (C): Carbon belongs to the group IV of Mendeleev's periodic table,

Hence, the formula of its oxide will be $CO_{2}.$

The general formula for the oxides of the element Aluminium (Al): Aluminum belongs to the group III of Mendeleev's periodic table,

Hence, the formula of its oxide will be $Al_{2}O_{3.}$

The general formula for the oxides of the element Silicon (Si): Silicon belongs to the group IV of Mendeleev's periodic table,

Hence, the formula of its oxide will be $SiO_{2.}$

The general formula for the oxides of the element Barium (Ba): Barium belongs to the group II of Mendeleev's periodic table,

Hence, the formula of its oxide will be $BaO.$

Besides gallium Scandium (Sc) and Germanium (Ge) elements have been discovered for which gaps were left by Mendeleev in his periodic table.

The criteria used by Mendeleev in creating his periodic table were:

(i) The atomic mass of the elements was used to arrange the elements.

(ii) Grouping the elements according to their similar chemical properties.

And hence proposed that the chemical properties of the elements are the periodic function of their atomic masses and thus he arranged the elements according to the increasing order of atomic masses.

Noble gases are inert nature elements. In the periodic table, they are placed in a separate group because they have a unique property and are very different from other elements.

## NCERT solutions for class 10 science chapter 5 Periodic Classification of Elements

Topic 5.3: Making order out of chaos: The Modern Periodic Table

Modern periodic table removes, various anomalies of Mendeleev's periodic table as follows:

(1) In the modern periodic table, elements are arranged in the increasing order of their atomic number, not in the atomic mass.

(2) In the modern periodic table, the isotopes are placed in the same place as they having the same atomic number but different atomic masses.

(3) Now, the same group elements have the same number of valence electrons.

(4) Hydrogen is now placed in the group containing the same valence electrons.

Elements that show similar chemical reactions are Beryllium (Be) and Calcium (Ca) because they belong to the same group. i.e., group 2nd in the modern periodic table

Q.3. (a)  Name

Single valence electron elements are: (a) Lithium, Sodium, and Potassium.

Q.3.(b)    Name

Magnesium and Calcium have two electrons in their outermost shells.

Q.3. (c)

The elements which have fully filled outermost shells are noble gases.

Example: Helium, Neon, and Argon.

Yes, they have the following similar properties:

(1) Belongs to the same group I in the periodic table.

(2) Have 1 valence electron in the valence shell.

(3) All are alkali metals.

(4) They are highly reactive.

Both Helium and Neon are noble gases which belong to the zero groups in the modern periodic table. They have fully filled the outermost shell with electrons. Helium has two electrons in its K shell whereas Neon has 8 electrons in its outermost shell.

Among the first ten elements metals are only 2 elements:

Lithium (Li) and Beryllium (Be).

•  $Ga \: \: \: Ge\: \: \: As\: \: \: \: Se \: \: \: \: Be$

The metallic character of the elements decreases as we move horizontally from left to right in the periodic table.

Therefore, Be will have the maximum metallic character because of its extreme left position in the periodic table.

## NCERT solutions for class 10 science chapter 5 Periodic classification of elements- Exercise solutions

(a) The elements become less metallic in nature.
(b) The number of valence electrons increases.
(c) The atoms lose their electrons more easily.
(d) The oxides become more acidic.

When going from left to right across the periods of the periodic table, the number of valence electrons increases. So, the tendency to lose electrons decreases whereas to accept electron increases.

Hence the option (C) is incorrect.

$(a) Na \; \; \; \; \; (b) Mg \; \; \; \; \; (c) AI \: \; \; \; \; \; (d) Si$

X must be Magnesium (Mg) which has a valency of 2 and when it combines with chlorine having valency 1, it forms $MgCl_{2}$.

Hence, the option (B) is correct.

Q.3.(a)    Which element has

The element which has two shells, which are both completely filled with electrons is,

Neon with electronic configuration $(2,8)$.

Q.3.(b)    Which element has

The given electronic configuration $(2,8,2)$ is of Magnesium (Mg).

Q.3.(c)

The element having three shells and four electrons in its valence shell is Silicon (Si).

Q.3. (d)   Which element has

The element having two shells and three electrons in its valence shell is Boron (B).

Q.3. (e)   Which element has

The element having twice as many electrons in its second shell as in its first shell will be:

Carbon with electronic configuration: $(2,4)$

The same column of the periodic table as boron belongs to the group 13th has 3 valence electrons,

Hence, its valency is 3.

Therefore, all the elements in the same column of the periodic table as Boron will have a valency of 3.

Fluorine belongs to the group 17th in the periodic table and having 1 valence electron.

Hence its valency is 1.

Therefore, all elements in the same column of the periodic table as fluorine will have a valency of 1.

(a)  What is the atomic number of this element?
(b)  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)

The electronic configuration: $(2,8,7)$ is of Chlorine.

(a) The atomic number of this element will be: $2+8+7 = 17$.

(b) It will be chemically similar to the element Fluorine (9) as it also has the same number of valence electrons in its valence shell.

Group 16         Group 17
-                    -
-                   A
-                    -
B                   C

As we know in the periodic table, group 3 - group 12 are transition metal and group 13 to group 16 are metalloid.and then there are halogens in 17 groups.

A is in group 17 so it is a non-metal.

Group 16    Group 17

-                 -
-                 A
-                 -
B                C

Element C is less reactive than A because in the halogens the reactivity decreases as we move down. This happens because as we move down the nuclear attraction increases due to an increase in atomic mass. Stronger attraction toward electron will make it harder to react with any other element that's why they are less reactive.

Group 16       Group 17
-                  -
-                 A
-                  -
B                 C

C is much smaller than the size of the B because C has a higher atomic mass which means higher attraction to the electron which means compact (less) size.

The electronic configuration of the element Nitrogen (N) is $(2,5)$.

The electronic configuration of the element phosphorus (P) is $(2,8,5)$

So, Nitrogen will be more electronegative than Phosphorus because its atom has a small size due to which the attraction of its nucleus for the incoming electron is more.

The electronic configuration of an element gives the distribution of electrons in various shells present in the element. The atoms with similar electronic configuration are placed in the same column, hence groups have the same number of valence electrons.

Group number can be known by knowing the number of valence electrons.

The number of shells present in an element is equal to the period number.

Thus, the information of electronic configuration is enough to know the group and period number of an element.

Element with atomic no. 12 and atomic no. 38 will have chemical properties the same as calcium. this is due to the fact that they have valency the same as calcium and also lie in the same group.

 Mendeleev's periodic table Modern periodic table Elements are arranged in the increasing order of their atomic masses Elements are arranged in the increasing order of their atomic numbers Consists of 8 groups Consists of 18 groups Groups are categorized into subgroups 'a' and 'b' No subdivision of groups. Noble gases were not grouped since they were not discovered yet Noble gases were grouped together at the end of the table. There was no place for isotopes Slots for isotopes present according to atomic number

## CBSE NCERT Solutions for Class 10 Science - Chapter wise

 Chapter No. Chapter Name Chapter 1 NCERT textbook solutions for class 10 science chapter 1 Chemical Reactions and Equations Chapter 2 Free NCERT solutions for class 10 science chapter 2 Acids, Bases, and Salts Chapter 3 Solutions of NCERT class 10 science chapter 3 Metals and Non-metals Chapter 4 CBSE NCERT solutions for class 10 science chapter 4 Carbon and its Compounds Chapter 5 NCERT solutions for class 10 science chapter 5 Periodic Classification of Elements Chapter 6 NCERT textbook solutions for class 10 science chapter 6 Life Processes Chapter 7 CBSE NCERT solutions for class 10 science chapter 7 Control and Coordination Chapter 8 NCERT solutions for class 10 science chapter 8 How do Organisms Reproduce? Chapter 9 NCERT textbook solutions for class 10 science chapter 9 Heredity and Evolution Chapter 10 Solutions for NCERT class 10 science chapter 10 Light Reflection and Refraction Chapter 11 NCERT textbook solutions for class 10 science chapter 11 The Human Eye and The Colorful World Chapter 12 Solutions for NCERT class 10 science chapter 12 Electricity Chapter 13 NCERT free solutions for class 10 science chapter 13 Magnetic Effects of Electric Current Chapter 14 NCERT textbook solutions for class 10 science chapter 14 Sources of Energy Chapter 15 CBSE NCERT solutions for class 10 science chapter 15 Our Environment Chapter 16 NCERT solutions for class 10 science chapter 16 Sustainable Management of Natural Resources

## Advantages of NCERT solutions for class 10 science chapter 5 Periodic classification of elements

• These solutions cover all the questions mentioned in the chapter.
• It's easy to understand.
• For each question, students will get a very good explanation of the question solution.
• Going through the free NCERT solution of the class 10 science chapter 5, students will be able to understand the theory behind every concept which helps them to solve the questions quickly and accurately.