Atomic Structure MCQs and Assertions

Atomic Structure - MCQ Section

• Bohr's Radius: The radius of the second Bohr orbit for hydrogen atoms is 0.529 Å.
• Third Shell Orbitals: The third shell contains 9 orbitals.
• Quantum of Light Wavelength: A quantum of light with a frequency of 6×10⁻¹⁵ s⁻¹ has a wavelength close to 50 nanometers.
• Atomic Structure Model Pioneer: The first scientist to propose a model for the structure of the atom was Ernest Rutherford.
• Angular Nodes of 4d Orbital: The 4d orbital has 2 angular nodes.
• Mass Number and Atomic Number: The mass number of a nucleus is sometimes equal to, always more than, or sometimes more than its atomic number.

Assertion-Reason Questions

• Black Body Radiation: A black body is an ideal body that absorbs and emits radiation of all frequencies.
• Radiation Frequency and Temperature: The frequency of radiation emitted by a body increases with increasing temperature.
• Electron Position and Momentum: It is impossible to simultaneously determine the exact position and momentum of an electron.
• Electron Path: The path of an electron in an atom is not clearly defined.
• Isotopes and Chemical Behavior: All isotopes of a given element show the same chemical behavior. Chemical properties are determined by the number of electrons in an atom.
• Atomic Neutrality: Atoms are electrically neutral because the number of protons and electrons are equal.

Section - B (SA I)

• Subshells for n=4: The subshells with m values for n=4 contain a total of 16 electrons.
• Uncertainty in Velocity and Wavelength: If the uncertainty in position of a moving electron equals its de Broglie wavelength, its velocity is completely uncertain.
• Electromagnetic Radiation Wavelength and Frequency: The wavelength of the electromagnetic radiation emitted by a transmitter broadcasting at 1,368 kHz is roughly equivalent to 219.2m.
• Electromagnetic Spectrum: The emitted radiation in this case would fall in the radio frequency (specifically the AM radio band) part of the electromagnetic spectrum.

Section - C (SA II)

• Quantum Numbers for n=2: For an orbital with n = 2, the possible values of l are 0 and 1, and the possible values of ml are -1, 0, and 1 .
• Quantum Numbers for 3d orbital: The quantum numbers m$_l$ and l of electrons within a 3d orbital are m$_l$ = -2, -1, 0, 1, 2 and l=2.
• Possible Orbitals: Examples of possible orbitals are 1s, 2p, 2d, and 3f. 2d is not a legitimate orbital.
• Other Notes: Note that the information provided about possible orbitals is somewhat limited; it focuses on the given options but does not cover all possible rules for orbital configuration. It's best to consult further resources for a comprehensive understanding of orbital validity.

Section - D (Case Based Questions)

• Orbital Properties: Orbitals are regions of space where electrons have high probability of being located, distinguished by their size, shape, and orientation. Smaller size indicates higher probability of finding electrons closer to the nucleus. Different orbital shapes and orientations determine the orbital's quantum number.

• Quantum Numbers: Spin quantum number determines the spin of an electron (which has two values, usually +1/2 or -1/2). Other quantum numbers define orbitals, and are more closely related to the energy, shape, and orientation of the spatial region where electrons are most likely to be.

• Orbital Representations: n=3 relates to orbitals and n=2, l=1 refers to a specific type of p orbital with angular momentum characteristics.

• Electron Capacity: Each orbital can hold a maximum of 2 electrons.

• s and p Orbital Shapes: 's' orbitals are spherical, while 'p' orbitals have a dumbbell shape.

• Bohr Model Limitations: The Bohr model, while useful for understanding the discrete energy levels of single electron atoms, has limitations. It cannot explain the spectra of multi-electron atoms, nor the finer details of atomic structure, such as those predicted by later models (like the quantum mechanical model).

• Exchange Energy: Stable orbitals (especially those that are half-filled or completely filled) are stabilized by exchange energy, which results from interactions between electrons with parallel spins. This is a crucial factor in orbital filling rules used in multi-electron atoms.

Section - E (LA)

• De Broglie Wavelength and Bohr Orbit: The circumference of the Bohr orbit is a multiple of the de Broglie wavelength in the case of Hydrogen.
• Heisenberg Uncertainty Principle Relevance: The uncertainty principle is crucial for understanding the behavior of microscopic particles such as electrons. For macroscopic objects, these uncertainties are practically negligible.
• Hund's Rule of Maximum Multiplicity: In a set of degenerate orbitals, the lowest energy configuration corresponds to the maximum number of unpaired electrons with parallel spins.
• Photon Energy and Photoelectric Effect: The energy of a photon of wavelength 4×10⁻⁷ m is (3.1 eV). The kinetic energy can be calculated using equations for photoelectric emission. The velocity could then be determined from the kinetic energy information, noting that 1 eV = 1.602 x 10⁻¹⁹ J.