Class 10 NCERT Solutions Periodic Classification of Elements

Class 10 NCERT Solutions Periodic Classification of Elements - NCERT Solutions prepared for CBSE students by the best teachers in Delhi.

Question 1: 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.z

Question 2: 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.

Question 3: What were the limitations of Newlands’ Law of Octaves?

Answer: Limitations of Newlands’ law of octaves:

(i) It was not applicable throughout the arrangements. It was applicable up to calcium only. The properties of the elements listed after calcium showed no resemblance to the properties of the elements above them.

(ii) Those elements that were discovered after Newlands’ octaves did not follow the law of octaves.

(iii) The position of cobalt and nickel in the group of the elements (F, Cl) of different properties could not be explained.

(iv) Placing of iron far away from cobalt and nickel, which have similar properties as iron, could also not be explained.

Question 4: Use Mendeleev’s Periodic Table to predict the formulae for the oxides of the following elements: K, C, Al, Si, Ba.


K is in group 1. Therefore, the oxide will be K2O.

C is in group 4. Therefore, the oxide will be CO2.

Al is in group 3. Therefore, the oxide will be Al2O3.

Si is in group 4. Therefore, the oxide will be SiO2.

Ba is in group 2. Therefore, the oxide will be BaO.

Question 5: Besides gallium, which other elements have since been discovered that were left by Mendeleev in his Periodic Table? (any two)

Answer: Scandium and germanium

Question 6: What were the criteria used by Mendeleev in creating his Periodic Table?

Answer: Mendeleev’s periodic table was based on the observation that the properties of elements are a periodic function of their atomic masses. This means that if elements are arranged in the increasing order of their atomic masses, then their properties get repeated after regular intervals.

Question 7:  Why do you think the noble gases are placed in a separate group?

Answer: Noble gases are inert elements. Their properties are different from the all other elements. Therefore, the noble gases are placed in a separate group.

Question 8: How could the Modern Periodic Table remove various anomalies of Mendeleev’s Periodic Table?

Answer: Mendeleev was unable to give fixed position to hydrogen and isotopes in the periodic table. In Mendeleev’s periodic table, the increasing manner of atomic mass of the elements is not always regular from one to its next. It was believed that a more fundamental property than atomic mass could explain periodic properties in a better manner.

It was Henry Moseley who demonstrated that atomic number of an element could explain periodic properties in a better way than atomic mass of an element and arranged the elements in increasing order of their atomic numbers. Then it was found that the various anomalies of Mendeleev’s periodic table were removed by the modern periodic table.

Question 9: Name two elements you would expect to show chemical reactions similar to magnesium. What is the basis for your choice?

Answer: Calcium (Ca) and strontium (Sr) are expected to show chemical reactions similar tomagnesium (Mg). This is because the number of valence electrons (2) is same in all these three elements. And since chemical properties are due to valence electrons, they show same chemical reactions.

Question 10: 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.

Answer: (a) Lithium (Li), sodium (Na), and potassium (K) have a single electron in their outermost shells.

(b) Magnesium (Mg) and calcium (Ca) have two electrons in their outermost shells.

(c) Neon (Ne), argon (Ar), and xenon (Xe) have filled outermost shells.

Students should free download the NCERT solutions and get better marks in exams. panel of teachers recommend students to practice questions in NCERT books and download NCERT solutions.



Click to View or Download pdf file
Click for more Science Study Material

Latest NCERT & CBSE News

Read the latest news and announcements from NCERT and CBSE below. Important updates relating to your studies which will help you to keep yourself updated with latest happenings in school level education. Keep yourself updated with all latest news and also read articles from teachers which will help you to improve your studies, increase motivation level and promote faster learning

Conduct of the practical work during the lockdown

CBSE has advised schools to follow the Alternative Calendar developed by NCERT to continue education during the lockdown through alternative modes to achieve learning outcomes. Schools have reportedly started using these calendars and other prescribed pedagogical...

National Online Painting Championship

The National Mission for Clean Ganga, Ministry of Jal Shakti in collaboration with Kalantar Art Trust is organizing KALANTAR-2020: National Online Painting Championship with the aim to provide a platform to youth and school children to demonstrate their artistic skills...

Training of CBSE School Teachers on Olabs

Training of CBSE School Teachers on Olabs in collaboration with C-DAC Mumbai: OLabs is a platform jointly developed by the Ministry of Electronics and Telecommunications, Government of India, CDAC, and Amrita University to facilitate a virtual experience of CBSE...

TERI Green Olympiad 2020

Green Olympiad is a value driven project conducted by TERI (The Energy and Resources Institute) for school students annually since 1999. This Olympiad assesses the environment quotient of students and also enhances their understanding on issues related to sustainable...

Keep your kids engaged during Lockdown

Kids are the Future of our Country! Outlines have changed and so should the formats of existence! It is the best time to teach our kids the pleasure of Self-Discipline, Self-Realization and Self-Control. To keep the future generation safe in such unpredictable...

NEP Transforming India Quiz

As a part of Shikshak Parv celebration, an online quiz competition on National Education Policy 2020 will be organized by the Ministry of Education, Govt. of India, from 5 th September to 25th September 2020 in order to create awareness about NEP among all stakeholders...

Studies Today