NCERT Solutions for Class 10 Science Unit 5

Periodic Classification of Elements Class 10

Unit 5 Periodic Classification of Elements Exercise Solutions

The periodic table is a tabular arrangement of the chemical elements, organized on the basis of their atomic number (number of protons in the nucleus), electron configurations, and recurring chemical properties. Elements are presented in order of increasing atomic number, which is typically listed with the chemical symbol in each box. The standard form of the table consists of a grid of elements laid out in 18 columns and 7 rows, with a double row of elements below that. The table can also be deconstructed into four rectangular blocks: the s-block to the left, the p-block to the right, the d-block in the middle, and the f-block below that.
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Question : Solutions of Questions on Page Number : 81

Q1 :  

Did Dobereiner's triads also exist in the columns of Newlands' Octaves? Compare and find out.


Answer :

Only one triad of Dobereiner's triads exists in the columns of Newlands' octaves. The triad formed by the elements Li, Na, and K of Dobereiner's triads also occurred in the columns of Newlands' octaves.

Dobereiner's triads

Li

Ca

Cl

Na

Sr

Br

K

Ba

I

Newlands' octaves

H

Li

Be

B

C

N

O

F

Na

Mg

Al

Si

P

S

Cl

K

Ca

Cr

Ti

Mn

Fe

Co and Ni

Cu

Zn

Y

In

As

Se

Br

Rb

Sr

Ce and La

Zr

-

-

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Q2 :  

What were the limitations of Dobereiner's classification?


Answer :

Limitation of Dobereiner's classification:

All known elements could not be classified into groups of triads on the basis of their properties.

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Q3 :  

What were the limitations of Newlands' Law of Octaves?


Answer :

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Q4 :  

Use Mendeleev's Periodic Table to predict the formulae for the oxides of the following elements:

K, C, Al, Si, Ba.


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Q5 :  

Besides gallium, which other elements have since been discovered that were left by Mendeleev in his Periodic Table? (any two)


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Q6 :  

What were the criteria used by Mendeleev in creating his Periodic Table?


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Q7 :  

Why do you think the noble gases are placed in a separate group?


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Q8 :  

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


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Q9 :  

Name two elements you would expect to show chemical reactions similar to magnesium. What is the basis for your choice?


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Q10 :  

Name

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

(b) two elements that have two electrons in their outermost shells.

(c) three elements with filled outermost shells.


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Q11 :  

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

(b) Helium is an unreactive gas and neon is a gas of extremely low reactivity. What, if anything, do their atoms have in common?


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Q12 :  

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


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Q13 :  

By considering their position in the Periodic Table, which one of the following elements would you expect to have maximum metallic characteristic?


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Exercise : Solutions of Questions on Page Number : 91

Q1 :  

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.

(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.


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Q2 :  

Element X forms a chloride with the formula XCl2, which is a solid with a high melting point. X would most likely be in the same group of the Periodic Table as

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


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Q3 :  

Which element has

(a) two shells, both of which are completely filled with electrons?

(b) the electronic configuration 2, 8, 2?

(c) a total of three shells, with four electrons in its valence shell?

(d) a total of two shells, with three electrons in its valence shell?

(e) twice as many electrons in its second shell as in its first shell?


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Q4 :  

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

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


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Q5 :  

An atom has electronic configuration 2, 8, 7.

(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)


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Q6 :  

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?


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Q7 :  

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?


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Q8 :  

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


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Q9 :  

In the Modern Periodic Table, calcium (atomic number 20) is surrounded by elements with atomic numbers 12, 19, 21, and 38. Which of these have physical and chemical properties resembling calcium?


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Q10 :  

Compare and contrast the arrangement of elements in Mendeleev's periodic Table and the Modern Periodic Table.


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Science : CBSE NCERT Exercise Solutions for Class 10th for Periodic Classification of Elements will be available online in PDF book form soon. The solutions are absolutely Free. Soon you will be able to download the solutions.

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