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

Q:

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) AI (d) Si

A:

(b) Mg

Reason: X would most likely be in the same group as of the Magnesium (Mg) in the Periodic Table because the formula of chloride of X (XCl2) suggests that the valency of X is +2.

Q:

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.

A:

(c) The atoms lose their electrons more easily.
Reason : When we move from left to right across the periods of the periodic table, the non-metallic character increases. Therefore, the tendency to lose electrons decreases.

Q:

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?

A:

The element with atomic number 12 (electronic configuration 2,8,2) and 38 (electronic configuration 2,8,2) have same chemical properties as that of calcium because both of them have same number of valence electrons (2) like calcium.

Q:

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)

A:

(a) The atomic number of this element is 17.
(b) It would be chemically similar to F (atomic number 9) having configuration as 2, 7 which means same number of valence electrons as the given element has.

Q:

(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?

A:

(a) All the elements in the same column as boron have the same number of valence electrons (3).

(b) All the elements in the same column as fluorine have the same number of valence electrons (7). All of them will have valency equal to -1.

Q:

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

A:

Electronic configuration of an element gives the information about number of shells and the number of valence electrons present in the element.

We can find the group number with the help of number of valence electrons.

Number of shells present in an element is equal to period in which this element is placed.

Thus, by knowing electronic configuration we know the group number and period number of an element, which indicates the position of an element in the periodic table.

Q:

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?

A:

Electronic configuration of Nitrogen is 2,5 and that of Phosphorus is 2, 8, 5.

Nitrogen will be more electronegative than phosphorus because electronegativity decreases on moving from top to bottom in a group.

Q:

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 non-metal.
(b) C is less reactive than A because reactivity decreases down the group in halogens.
(c) C will be smaller in size than B because on moving from left to right in a period, the nuclear charge increases and therefore, electrons come closer to the nucleus.
(d) Element A will form an anion because it accepts an electron to complete its octet.

Q:

Compare and contrast the arrangement of elements in Mendeléev’s Periodic Table and the Modern Periodic Table.

A:

S.No.

Mendeleev’s periodic table

Modern periodic table

1.

Elements are arranged in the increasing order of their atomic masses.

Elements are arranged in the increasing order of their atomic numbers.

2.

No place for isotopes.

No such problem occurs as elements are arranged on the basis of their atomic numbers.

3.

Groups were divided in subgroups A and B.

Groups are not subdivided.

4.

It has 8 groups.

It has 18 groups.

Q:

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?

A:

(a) Neon. It has two shells, both of which are completely filled with electrons (2 electrons in K shell and 8 electrons in L shell).

(b) Magnesium. Its electronic configuration is 2, 8, 2.

(c) Silicon. It has a total of three shells, with four electrons in its valence shell (2 electrons in K shell, 8 electrons in L shell and 4 electrons in M shell).

(d) Boron. It has a total of two shells, with three electrons in its valence shell (2 electrons in K shell and 3 electrons in L shell).

(e) Carbon. It has twice as many electrons in its second shell as in its first shell (2 electrons in K shell and 4 electrons in L shell).

Benefits of NCERT Solutions

NCERT Solutions for Class 10 contain immensely significant points and for every chapter, each concept is simplified so that it turns out to be easy to remember that expands the odds of scoring commendably in the board exams. NCERT Solutions for class 10 by Extramarks is the best reference material for test preparation. Given below are a couple of points about how these solutions help in exam preparation.
1. It helps students practice loads of questions from every chapter which encourages them to make their concepts more grounded..

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3. These solutions are the best examination materials to know your weak and strong points. It is essential to work on your weak points to score well in the exams. 

4. Most of the questions in exams are asked in a similar arrangement from NCERT textbooks. Hence, students should altogether revise every chapter’s solution to get a good command in subjects

Tips & Strategies for Class 10 Exam Preparation

1. Make a timetable to complete your syllabus and make time for revision.

2. Refer to NCERT Solutions given on the Extramarks website to clear your concepts anytime while preparing for your exams.

3. Start studying with the help of Extramarks – The Learning App to pass your exams with flying colours. It provides complete study material with solved and unsolved papers.

4. It is important to clear all your doubts before the exam with your teachers or Alex (an AI studybot).

5. While reading or learning a chapter, make sure to make notes with algorithms, formulas, theorems, etc., and study them for a quick revision before exams.

6. Practice an ample number of question papers to make your concepts stronger.

7. Take rest and a proper meal. Don’t stress too much.

Why opt for Extramarks NCERT Solutions for Class 10 ?

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