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SEBA Class 10 Science Chapter 5 Periodic Table Extra Questions and Answers | Modern Periodic Table Notes

SEBA Class 10 Science Chapter 5 – Periodic Table Extra Questions and Answers

This post contains important extra questions and answers from SEBA Class 10 Science Chapter 5 – Periodic Table and Periodicity in Properties. These questions are very helpful for board exam preparation, revision, and understanding important concepts clearly.

These extra questions (Chapter 5) cover topics like periodic trends, atomic size, valency, modern periodic law, and arrangement of elements.

Q: What was Döbereiner’s Triad?

A: Döbereiner’s Triads were groups of three elements with similar chemical properties in which the atomic mass of the middle element was approximately equal to the average of the atomic masses of the other two elements.

Q: What was the main limitation of Döbereiner’s Triads?

A: The main limitation of Döbereiner’s Triads was that only a few elements could be grouped into triads, and many known elements did not fit into this classification system.

Q: State Newlands’ Law of Octaves.

A: Newlands’ Law of Octaves states that when elements are arranged in increasing order of atomic mass, every eighth element has properties similar to those of the first element, just like musical notes repeat after every seventh note.

Q: Why is it called the “Law of Octaves”?

A: It is called the Law of Octaves because, similar to musical octaves where the eighth note repeats the first, every eighth element shows similar properties to the first element when arranged by increasing atomic mass.

Q: Why did Newlands’ Law of Octaves fail?

A: Newlands’ Law of Octaves failed because it was applicable only up to calcium, he placed two elements like cobalt and nickel in the same position, dissimilar elements were sometimes grouped together, and it could not explain the properties of elements discovered later.

Q: Who is known as the “Father of the Periodic Table”?

A: Dmitri Ivanovich Mendeleev, a Russian chemist, is known as the Father of the Periodic Table for developing the first systematic periodic table in 1869.

Q: State Mendeleev’s Periodic Law.

A: Mendeleev’s Periodic Law states that the properties of elements are a periodic function of their atomic masses.

Q: What were the rows and columns in Mendeleev’s Periodic Table called?

A: In Mendeleev’s Periodic Table, the horizontal rows were called periods and the vertical columns were called groups.

Q: How did Mendeleev arrange the elements?

A: Mendeleev arranged the elements in increasing order of atomic mass such that elements with similar properties were placed in the same group.

Q: Name three elements Mendeleev predicted.

A: Mendeleev predicted the existence of elements such as scandium (eka-boron), gallium (eka-aluminium), and germanium (eka-silicon), whose properties were later found to match his predictions.

Q: State one limitation of Mendeleev’s table related to hydrogen.

A: One limitation of Mendeleev’s periodic table related to hydrogen was that hydrogen could be placed either in Group 1 or Group 17, which created confusion about its correct position.

Q: Who improved Mendeleev’s table using atomic number?

A: Henry Moseley improved Mendeleev’s periodic table by introducing atomic number as the basis of classification in 1913.

Q: State the Modern Periodic Law.

A: The Modern Periodic Law states that the properties of elements are a periodic function of their atomic numbers.

Q: How many groups and periods are there in the Modern Periodic Table?

A: The Modern Periodic Table consists of 18 groups (vertical columns) and 7 periods (horizontal rows).

Q: What determines the position of an element in a group?

A: The position of an element in a group is determined by the number of valence electrons present in its atom.

Q: What determines the position of an element in a period?

A: The position of an element in a period is determined by the number of electron shells occupied in its atom.

Q: What is the formula to calculate the maximum number of electrons in a shell?

A: The maximum number of electrons in a shell is calculated using the formula 2n², where n represents the shell number such as K = 1, L = 2, and so on.

Q: Define atomic size.

A: Atomic size is defined as the distance between the nucleus and the outermost shell of an atom.

Q: How does atomic size change across a period and down a group?

A: Atomic size decreases across a period because the nuclear charge increases and pulls electrons closer, whereas atomic size increases down a group due to the addition of new electron shells.

Q: Define valency and state how it varies.

A: Valency is the combining capacity of an element. In a group, valency remains the same, while in a period it first increases and then decreases.

Q: How does metallic and non-metallic character vary in the periodic table?

A: Metallic character decreases across a period and increases down a group, whereas non-metallic character increases across a period and decreases down a group.

Q. What are the Advantages of Mendeleev’s Classification

A:- Advantages of Mendeleev’s Classification are:-

1. Elements with similar properties were placed together in the same group.
2. Mendeleev left empty spaces for undiscovered elements and predicted their properties accurately.
3. He corrected the atomic masses of several elements based on their positions in the table.
4. The classification made the study of elements simpler and more organized.

Q: What are the Disadvantages of Mendeleev’s Classification

A: Disadvantages of Mendeleev’s Classification

1. Hydrogen resembles both alkali metals and halogens, so its position was not fixed properly.
2. Isotopes have different atomic masses but similar properties. Mendeleev’s table could not accommodate them correctly.
3. Some elements had to be placed against the order of increasing atomic mass (e.g., Argon and Potassium, Cobalt and Nickel).
4. Lanthanides and actinides were not given separate positions.

Q: What are the Advantages of Newlands’ Law of Octaves

A: Advantages of Newlands’ Law of Octaves

1. It was the first attempt to classify elements systematically according to their increasing atomic masses.
2. It showed that the properties of elements repeat after regular intervals.
3. It grouped many elements with similar chemical properties together.
4. It laid the foundation for the development of the modern periodic table

Q: What are the Disadvantages of Newlands’ Law of Octaves

A: Disadvantages of Newlands’ Law of Octaves

1. The law was applicable only up to calcium and failed for heavier elements.
2. Newlands did not leave any vacant spaces for undiscovered elements.
3. Some elements with different properties were placed in the same group.
4. Some elements with similar properties were placed in different groups.
5. The periodic repetition of properties after every eighth element was not valid for all known elements.

Q. Difference between Modern Periodic Table and Mendeleev’s Periodic Table.

Modern Periodic Table	Mendeleev’s Periodic Table
The modern periodic table is based on the atomic number of elements.	Mendeleev’s periodic table is based on the atomic mass of elements.
It states that the properties of elements are a periodic function of their atomic numbers.	It states that the properties of elements are a periodic function of their atomic masses.
Elements are arranged in increasing order of atomic number, so the arrangement is more accurate and systematic.	Elements were arranged in increasing order of atomic mass, which caused some irregularities in arrangement.
Isotopes have the same atomic number, so they occupy the same position in the periodic table.	Isotopes could not be properly explained in this periodic table.
Hydrogen has a more logical position based on atomic number, although it still shows some unique behaviour.	The position of hydrogen was not clearly defined in this periodic table.
Noble gases are placed in a separate group called Group 18.	Noble gases were not included in the original periodic table.
There are no major anomalies in the arrangement of elements.	Some elements were placed in the wrong order, such as cobalt and nickel.

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SEBA Class 10 Science Chapter 5, Periodic Table Extra Questions, Chapter 5 Science Notes SEBA, Modern Periodic Table Questions, Class 10 Chemistry Important Questions, Atomic Number, Valency, Periodic Trends, SEBA Board Exam 2026

These SEBA Class 10 Science Chapter 5 extra questions will help students revise quickly and score better marks in exams. Practice regularly for better understanding.