COMEDK UGET 2025 Atomic Structure Practice Questions with Solutions

COMEDK UGET 2025 Atomic Structure Practice Questions with Solutions: The chapter of Atomic Structure holds a good weightage in the COMEDK UGET 2025 Chemistry syllabus . The COMEDK UGET 2025 Apomic Structure practice questions will include various important topics such as Atomic Models, Quantum Mechanical Model, Shapes of Atomic Orbitals etc. With an approximate weightage around 8%, you can expect at least 1-5 questions from Atomic Structure in the upcoming COMEDK UGET 2025 exam . The COMEDK 2025 syllabus covers topics from 11th as well as 12th standard. Therefore, you are advised not only to mug up the topics from the syllabus, but also solve the COMEDK Atomic Structure practice questions 2025 from time to time. After you do this, you will not only be able to get an idea about the question type, difficulty level, exam pattern etc. but it will also help you in getting acquainted with the questions that are repeated in the exam. In this article, we will be talking about the COMEDK UGET 2025 Atomic Structure practice questions with solutions, with the help of which you can prepare well for the exam and ensure a good chance of passing with flying colours.

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COMEDK UGET 2025 Atomic Structure Important Topics

With various subtopics like Atomic Models, Quantum Mechanical Model etc. included, the Atomic Structure chapter plays a pivotal role in the COMEDK exam preparation. Therefore, you are advised to have a good knowledge of all the chapters involved in Atomic Structure, as a major chunk of the exam will be based on this chapter. Find the list of COMEDK UGET 2025 Atomic Structure sub topics for exam preparation below:-

COMEDK UGET 2025 Atomic Structure Expected Weightage

If you are appearing for COMEDK UGET, you must know about the weightage and the number of questions related to the topic of Atomic Structure. Having this information will allow you to plan your preparation strategically. The table below provides an overview of the COMEDK UGET Atomic Structure expected weightage and the number of questions in the exam paper:-

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COMEDK UGET 2025 Atomic Structure Practice Questions with Solutions

Regularly practicing COMEDK UGET Atomic Structure sample questions can greatly improve your exam preparation. Solving COMEDK Atomic Structure practice questions with solutions helps you become familiar with possible exam questions, confirm correct answers, and grasp step-by-step solutions. Below are some key COMEDK UGET 2025 Atomic Structure practice questions, expertly curated from past exam papers:-

Q1. What are the Principal & Azimuthal quantum number values of the valence electrons in tripositive Lutetium?

a) n = 4 & 1 = 2

b) n = 5 & 1 = 2

c) n = 5 & 1 = 3

d) n = 4 & 1 = 3

Correct Answer - d) n = 4 & 1 = 3

Explanation: To determine the principal (n) and azimuthal (l) quantum numbers of the valence electrons in tripositive Lutetium (Lu3+), we need to first determine the electronic configuration of neutral Lutetium (Lu).

Neutral Lutetium has an atomic number of 71. Its electron configuration is:

Lu: [Xe] 4⨑ ¹ 45d16s ²

In the tripositive state (Lu3+), three electrons are removed. The electrons are generally removed from the outermost orbitals first. Thus, removing three electrons from neutral Lutetium involves the removal of two 6s electrons and one 5d electron:

Lu3+ : [Xe]4⨑ ¹⁴

Therefore, the valence electrons in Lu3+ are in the 4f subshell. The principal quantum number n for the 4f subshell is 4, and the azimuthal (angular momentum) quantum number l for the f subshell is 3.

So, the correct set of quantum numbers for the valence electrons in tripositive Lutetium is:

N = 4 & l = 3

Therefore, the correct option is:

D

Q2. A statement of Assertion followed by a statement of Reason is given. Choose the correct answer out of the following options

Assertion: Energy of 2s orbital of Hydrogen is less than the energy of the 2s orbital of Lithium.

Reason: Energies of orbitals in the same subshell decrease with increase in atomic number.

a) Both Assertion and Reason are correct and Reason is the correct explanation of Assertion.

b) Assertion is correct but Reason is an incorrect statement.

c) Assertion is incorrect but Reason is correct statement.

d) Both Assertion and Reason are incorrect statements.

Correct Answer - c) Assertion is incorrect but Reason is correct statement

Explanation:

In a hydrogen atom, the 2s orbital is occupied by a single electron, and there are no other electrons causing repulsions. The energy of the 2s orbital in hydrogen is determined only by the attraction between the nucleus (+1 charge) and the electron.

In lithium (Z=3), the 2s orbital experiences electron shielding due to the presence of two inner 1s electrons. These inner electrons partially shield the outer 2s electron from the full nuclear charge, making the effective nuclear charge (Z _eff ​) lower.

Because of this shielding, the 2s electron in lithium is less tightly bound compared to the single 2s electron in hydrogen. This means the energy of the 2s orbital in lithium is higher than in hydrogen (i.e., it is less negative).

Since the assertion states that the energy of the 2s orbital of hydrogen is less than that of lithium, this is incorrect.

Reason: Energies of orbitals in the same subshell decrease with an increase in atomic number.

In multi-electron atoms, as the atomic number increases, the effective nuclear charge (Z _eff ) also increases, leading to a stronger attraction between the nucleus and the electrons.

This stronger attraction pulls electrons closer, reducing the energy of the orbitals (making them more negative).

Therefore, this statement is correct because, in general, orbital energies decrease with increasing atomic number, despite shielding effects.

Choosing the correct answer:

The Assertion is incorrect (since the 2s orbital of hydrogen actually has lower energy than lithium).

The Reason is correct (because orbital energies generally decrease with increasing atomic number).

Thus, the correct answer is:

C - Assertion is incorrect but Reason is correct statement.

Q3. The mass number of an element X is 175 with 104 neutrons in its nucleus. Into which one of the following orbitals will the last electron enter?

a) 5s

b) 6s

c) 5d

d) 4f

Correct Answer - c) 5d

Explanation: The mass number of an element, denoted as A, is given by the sum of the number of protons (atomic number Z) and the number of neutrons (symbolized as N). The relationship can be expressed as:

A = Z+N

In this case, the mass number A is 175 and the number of neutrons N is 104. To find the atomic number (Z), we can rearrange the equation as:

Z = A-N

Substituting the given values:

Z = 175 - 104 = 71

So, the atomic number Z of the element is 71, which corresponds to the element Lutetium (Lu) in the periodic table, Lutetium has an atomic number of 71, meaning it has 71 protons and, in a neutral atom, 71 electrons.

The arrangement of electrons in the orbitals follows the Aufbau principle, which states that electrons occupy the lowest energy orbitals available. The order of filling the orbitals is generally given by the sequence dictated by the increasing energy levels:

1s, 2s, 2p, 3s, 3p, 4s, 3d, 4p, 5s, 4d, 5p, 6s, 4f, 5d, 6p, 7s, 5f, 6d, 7p

For elements with an atomic number of 71, the electron configuration is:

[Xe]4⨑ ¹ 45d ¹ 6s ²

Here, [Xe] represents the noble gas core for Xenon (atomic number 54). Beyond this core, the electrons fill the 4f, 5d, and 6s orbitals.

From the given electron configuration, the last electron enters the 5d orbital.

Therefore, the correct answer is:

Option C

Q4. Minimum number of nodes are present in:

a) 2s

b) 3s

c) 4s

d) 5s

Correct Answer - a) 2s

Explanation: Total number of nodes is given by (n-1)

2s = (2-1) = 1

3s = (3-1) = 2

4s = (4-1) = 3

5s = (5-1) = 4

Q5. The spectrum of He+ is similar to:

a) H

b) Li+

c) NA

d) He+

Correct Answer - a) H

Explanation: As He+ and H contain same number of electron. So, they show same type of spectra.

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