de Broglie & Heisenberg in Chemistry
Atomic Structure
9
JEE Qs
8%
Hard
60
min
Master the formulas, understand the conceptual implications of both principles, and pay meticulous attention to unit conversions for problem-solving.
🧮 Key Formulas
✅ Key Points for JEE
- 1De Broglie's hypothesis attributes wave nature to all matter, with observable effects primarily for microscopic particles due to Planck's constant (h) being extremely small.
- 2Heisenberg's Uncertainty Principle imposes a fundamental limit on the precision with which conjugate physical properties (like position and momentum, or energy and time) of a particle can be known simultaneously.
- 3Relating de Broglie wavelength to kinetic energy and accelerating potential (for charged particles) is crucial for numerical problems.
- 4The 'h' in Heisenberg's principle is Planck's constant, not the reduced Planck's constant (h-bar), and the inequality (>=) is significant, indicating a minimum uncertainty.
- 5Correct unit conversions (e.g., mass in kg, velocity in m/s, energy in J) are paramount for accurate calculations.
⚠️ Common Mistakes
- ✕Using incorrect units for mass (e.g., grams instead of kilograms) or velocity (e.g., cm/s instead of m/s) in calculations.
- ✕Confusing Planck's constant (h) with the reduced Planck's constant (ħ = h/2π) in the Heisenberg Uncertainty Principle formulas.
- ✕Misinterpreting the Heisenberg Uncertainty Principle as an experimental measurement error rather than a fundamental property of quantum systems.
- ✕Incorrectly converting energy units (e.g., eV to J) or charges (e.g., elementary charge to Coulombs) when solving problems involving potential difference.
- ✕Applying de Broglie's wavelength concept to macroscopic objects with an expectation of observable wave properties.
📝 Practice Questions
See allQ57.Given below are two statements : Statement (I) : For a given shell, the total number of allowed orbitals is given by n2 . Statement (II) : For any subshell, the spatial orientation of the orbitals is given by −l to +l values including zero. In the light of the above statements, choose the correct answer from the options given below : (1) Both Statement I and Statement II are false (2) Statement I is true but Statement II is false (3) Both Statement I and Statement II are true (4) Statement I is false but Statement II is true
Q57.In a multielectron atom, which of the following orbitals described by three quantum numbers will have same energy in absence of electric and magnetic fields? A. n = 1, l = 0, m1 = 0 B. n = 2, l = 0, m1 = 0 C. n = 2, l = 1, m1 = 1 D. n = 3, l = 2, m1 = 1 E. n = 3, l = 2, m1 = 0 Choose the correct answer from the options given below: (1) B and C Only (2) A and B Only (3) C and D Only (4) D and E Only
Q51.Radius of the first excited state of Helium ion is given as : a0 → radius of first stationary state of hydrogen atom. (1) r = 4a0 (2) r = 2a0 (3) r = a02 (4) r = a04
Q62.Given below are two statements : Statement (I) : A spectral line will be observed for a 2px →2py transition. Statement (II) : 2Px and 2py are degenerate orbitals. In the light of the above statements, choose the correct answer from the options given below : (1) Both Statement I and Statement II are true (2) Statement I is false but Statement II is true (3) Both Statement I and Statement II are false (4) Statement I is true but Statement II is false
Q51.For hydrogen atom, the orbital/s with lowest energy is/are : (A) 4 s (B) 3px (C) 3 dx2−y2 (D) 3 dz2 (E) 4pz Choose the correct answer from the options given below : (1) (B), (C) and (D) only (2) (A) and (E) only (3) (A) only (4) (B) only
Q44.The frequency of revolution of the electron in Bohr's orbit varies with n, the principal quantum number as (1) 1 (2) 1 n4 n2 (3) 1 (4) 1 n n3
NCERT Chapters
- Class 11 Chemistry Ch 2: Structure of Atom
- Class 11 Physics Ch 2: Units and Measurements
- Class 11 Physics Ch 6: Work, Energy and Power