Loading PDF...
Chapter Analysis
Intermediate45 pages • EnglishQuick Summary
Chapter 2, 'Structure of Atom' of NCERT Chemistry for Class 11 explores the discovery and features of fundamental particles like electrons, protons, and neutrons, leading to different atomic models such as Thomson's, Rutherford's, and Bohr's models. It elaborates on the quantum mechanical model of the atom, explaining the nature of electromagnetic waves, quantum numbers, and electron configurations in atoms. Additionally, it discusses the de Broglie relation, Heisenberg uncertainty principle, and the photoelectric effect, providing a comprehensive understanding of atomic structure.
Key Topics
- •Discovery of subatomic particles
- •Thomson, Rutherford, and Bohr atomic models
- •Quantum mechanical model of the atom
- •Planck’s quantum theory and photoelectric effect
- •de Broglie relation and Heisenberg uncertainty principle
- •Quantum numbers and atomic orbitals
- •Aufbau principle, Pauli exclusion principle, and Hund’s rule
- •Electronic configurations of elements
Learning Objectives
- ✓Understand the discovery and properties of electrons, protons, and neutrons
- ✓Explain different atomic models and their limitations
- ✓Describe the quantum mechanical model and its implications for electron behavior
- ✓Apply principles of quantum mechanics to explain atomic and molecular structures
- ✓Utilize quantum numbers to discuss atomic orbitals
- ✓Accurately write electronic configurations for various elements
Questions in Chapter
Calculate the number of electrons which will together weigh one gram.
Page 69
Calculate the mass and charge of one mole of electrons.
Page 69
Calculate the total number of electrons present in one mole of methane.
Page 69
Find (a) the total number and (b) the total mass of neutrons in 7 mg of 14C.
Page 69
Additional Practice Questions
Describe the experimental setup and conclusion of the Rutherford alpha-particle scattering experiment.
mediumAnswer: The Rutherford alpha-particle scattering experiment used a gold foil and directed a stream of alpha particles at it. Most particles passed through, but some were deflected at large angles. This led to the conclusion that atoms have a small, dense, positively charged nucleus.
Explain why the Bohr model could not explain the spectrum of elements other than hydrogen.
hardAnswer: The Bohr model could not explain multi-electron spectra because it did not account for electron-electron interactions, and it treated electrons as particles in fixed orbits, ignoring their wave nature.
What is the significance of the Heisenberg uncertainty principle in the quantum mechanical model of the atom?
hardAnswer: The Heisenberg uncertainty principle states that we cannot precisely know both the position and momentum of an electron simultaneously, which implies that electrons do not move in fixed orbits but exist in probability clouds, influencing the quantum mechanical model.
Define the Pauli exclusion principle and its role in electron configurations.
mediumAnswer: The Pauli exclusion principle states that no two electrons in an atom can have the same set of four quantum numbers, ensuring that electrons in an atom occupy distinct states, affecting the arrangement of electrons in various orbitals.
How does the quantum mechanical model differ from classical atomic models?
mediumAnswer: The quantum mechanical model treats electrons as wave-like particles existing in orbitals rather than fixed paths, accounting for the dual nature of matter, unlike classical models which viewed electrons as particles in specific orbits.