Consider the following statements and choose the correct option: (i) The orbital angular momentum of an electron in a $2s$ orbital is zero. (ii) The orbital angular momentum of an electron in a $2p$ orbital is $\sqrt{2}\,\frac{h}{2\pi}$.

Neither (i) nor (ii) is correct

Assertion (A): The ground-state electronic configuration of chromium (Z $=24$) is $[\text{Ar}]3d^5 4s^1$ and not $[\text{Ar}]3d^4 4s^2$. Reason (R): A half-filled $d$ subshell gives extra stability. Choose the correct option.

Both A and R are true and R is the correct explanation of A

Both A and R are true but R is not the correct explanation of A

Chapter testChemistryIncluded in the seriesTest 4 of 16

Bihar Board Class 11 Science Chemistry · Ch 2: Structure of Atom

Bihar Board Class 11 Science Chemistry · Ch 2: Structure of Atom is an online chapter test in the Bihar Board Class 11 Science pattern, covering Structure of Atom. Attempt it on SeatBeat with a timer like the real exam, then see a detailed solution for every question and your score and weak-topic analysis.

Questions

Minutes

Marks

None

Negative marking

Unlock all 16 tests — ₹149 Try Biology · Ch 1: The Living World free →

Topics in this test

Topic	Subject	Questions
Structure of Atom	Chemistry	30

Difficulty: 7 medium · 23 hard

Structure of Atom MCQ questions with answers

The first 3 of 30 questions. Unlock the series for the rest, each with a solution.

Q1. The energy of an electron in the ground state of the hydrogen atom is $-13.6\ \text{eV}$. What is the minimum energy required to remove the electron completely from the atom when it is present in the second excited state?
हाइड्रोजन परमाणु की निम्नतम अवस्था (ground state) में एक इलेक्ट्रॉन की ऊर्जा $-13.6\ \text{eV}$ है। जब इलेक्ट्रॉन द्वितीय उत्तेजित अवस्था (second excited state) में उपस्थित हो, तो उसे परमाणु से पूर्णतः निकालने के लिए आवश्यक न्यूनतम ऊर्जा कितनी होगी?
- A. $13.6\ \text{eV}$
- B. $3.40\ \text{eV}$
- C. $0.85\ \text{eV}$
- D. $1.51\ \text{eV}$
Solution
The second excited state means $n=3$ (ground state is $n=1$, first excited $n=2$). Its energy is $E_3 = \frac{-13.6}{3^2} = -1.51\ \text{eV}$, so removing the electron needs $+1.51\ \text{eV}$.
द्वितीय उत्तेजित अवस्था का अर्थ है $n=3$ (निम्नतम अवस्था $n=1$ है, प्रथम उत्तेजित अवस्था $n=2$)। इसकी ऊर्जा $E_3 = \frac{-13.6}{3^2} = -1.51\ \text{eV}$ है, अतः इलेक्ट्रॉन को निकालने के लिए $+1.51\ \text{eV}$ की आवश्यकता होती है।
Q2. Consider the following statements and choose the correct option: (i) The orbital angular momentum of an electron in a $2s$ orbital is zero. (ii) The orbital angular momentum of an electron in a $2p$ orbital is $\sqrt{2}\,\frac{h}{2\pi}$.
निम्नलिखित कथनों पर विचार कीजिए और सही विकल्प चुनिए: (i) $2s$ कक्षक में इलेक्ट्रॉन का कक्षीय कोणीय संवेग शून्य होता है। (ii) $2p$ कक्षक में इलेक्ट्रॉन का कक्षीय कोणीय संवेग $\sqrt{2}\,\frac{h}{2\pi}$ होता है।
- A. Only (i) is correct / केवल (i) सही है
- B. Both (i) and (ii) are correct / (i) और (ii) दोनों सही हैं
- C. Neither (i) nor (ii) is correct / न तो (i) और न ही (ii) सही है
- D. Only (ii) is correct / केवल (ii) सही है
Solution
Orbital angular momentum $=\sqrt{l(l+1)}\frac{h}{2\pi}$; for $2s$, $l=0$ gives $0$, and for $2p$, $l=1$ gives $\sqrt{2}\frac{h}{2\pi}$, so both statements are correct.
कक्षीय कोणीय संवेग $=\sqrt{l(l+1)}\frac{h}{2\pi}$; $2s$ के लिए $l=0$ से $0$ प्राप्त होता है, तथा $2p$ के लिए $l=1$ से $\sqrt{2}\frac{h}{2\pi}$ प्राप्त होता है, अतः दोनों कथन सही हैं।
Q3. Assertion (A): The ground-state electronic configuration of chromium (Z $=24$) is $[\text{Ar}]3d^5 4s^1$ and not $[\text{Ar}]3d^4 4s^2$. Reason (R): A half-filled $d$ subshell gives extra stability. Choose the correct option.
अभिकथन (A): क्रोमियम (Z $=24$) का मूल अवस्था इलेक्ट्रॉनिक विन्यास $[\text{Ar}]3d^5 4s^1$ है, न कि $[\text{Ar}]3d^4 4s^2$। कारण (R): अर्ध-भरित $d$ उपकोश अतिरिक्त स्थायित्व प्रदान करता है। सही विकल्प चुनिए।
- A. Both A and R are true but R is not the correct explanation of A / A और R दोनों सत्य हैं परंतु R, A की सही व्याख्या नहीं है
- B. A is false but R is true / A असत्य है परंतु R सत्य है
- C. Both A and R are true and R is the correct explanation of A / A और R दोनों सत्य हैं और R, A की सही व्याख्या है
- D. A is true but R is false / A सत्य है परंतु R असत्य है
Solution
Both statements are true and the half-filled $3d^5$ stability is exactly the reason Cr adopts the $3d^5 4s^1$ configuration.
दोनों कथन सत्य हैं तथा अर्ध-भरित $3d^5$ का स्थायित्व ही ठीक वह कारण है जिसके कारण Cr $3d^5 4s^1$ विन्यास ग्रहण करता है।

Frequently asked questions

How many questions are in the Bihar Board Class 11 Science Chemistry · Ch 2: Structure of Atom?

30 questions for 30 marks, to be answered in 20 minutes.

Is there negative marking in the Bihar Board Class 11 Science Chemistry · Ch 2: Structure of Atom?

No — wrong answers are not penalised in this test.

Which topics does the Bihar Board Class 11 Science Chemistry · Ch 2: Structure of Atom cover?

Structure of Atom (30 questions).

Is the Bihar Board Class 11 Science Chemistry · Ch 2: Structure of Atom free?

It is part of the BSEB Class 11 Science Test Series 2027 — Chapter-wise + Full Tests (16 tests, ₹149). You can first try Biology · Ch 1: The Living World for free.

More tests in the BSEB Class 11 Science Test Series 2027 — Chapter-wise + Full Tests

See the full BSEB Class 11 Science Test Series 2027 — Chapter-wise + Full Tests → · Bihar Board Class 11 Science: pattern, notification & syllabus →

₹149

View the full series