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Questions and Answers
What is the total mass number of an atom composed of 6 protons and 8 neutrons?
Which atomic model proposed that an atom is a sphere of positive charge with electrons embedded within it?
What do you call atoms that have the same number of neutrons but different numbers of protons?
What property of a wave is defined as the distance between two neighboring crests?
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Which of the following accurately defines the concept of isobars?
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What is the approximate relative mass of a neutron compared to a proton?
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What charge do neutrons carry?
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What does the term 'isoelectronic' refer to?
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What does the amplitude of a wave determine?
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Which spectral series corresponds to the visible region?
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What is the relationship between energy of ejected electrons and the frequency of incoming radiation in the photoelectric effect?
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What is the minimum frequency required for the ejection of electrons called?
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In Bohr's model of the hydrogen atom, which of the following is true about electron energy levels?
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What is the formula for the energy absorbed or released during an electron jump between energy levels?
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What does the Rydberg formula calculate for hydrogen-like atoms?
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What does Planck’s quantum theory state about energy?
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Study Notes
Subatomic Particles
- Electrons have a relative mass of 1/1836, approximately 9.109×10–31 kg, and a charge of -1.602×10–19 C.
- Protons have a relative mass of 1, approximately 1.673×10–27 kg, and a charge of +1.602×10–19 C.
- Neutrons have a relative mass of 1, approximately 1.675×10–27 kg, and no charge.
Atomic Models
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Thomson's Model (Plum-Pudding Model):
- Proposes atoms are spheres of positive charge with electrons embedded.
- Limitations include inability to explain Rutherford's scattering experiment results.
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Rutherford's Model:
- Suggests most mass and positive charge are concentrated in the nucleus, with electrons revolving around it.
- Limitations include failure to explain atomic stability and electronic structure.
Atomic Terms
- Atomic Number (Z): Total number of protons (and electrons in neutral atoms).
- Mass Number (A): Sum of protons and neutrons in an atom.
- Nucleons: Collective term for protons and neutrons.
- Isotopes: Same atomic number, different mass number (e.g. ¹H¹, ¹H², ¹H³).
- Isobars: Different atomic numbers but the same mass number (e.g. ¹⁵P³² and ¹⁶S³²).
- Isotones: Same number of neutrons but different protons/mass numbers (e.g. ⁶C¹⁴, ⁸O¹⁶, ⁷N¹⁵).
- Isoelectronic Species: Same electron count (e.g. N₂, CO, CN⁻).
- Nuclear Isomers: Same atomic number and mass number, different radioactive properties (e.g., Uranium-X and Uranium-Z).
- Isosters: Same number of atoms and electrons (e.g., N₂ and CO).
Wave Properties
- Wavelength (λ): Distance between consecutive crests or troughs.
- Frequency (ν): Number of waves passing a point per second; related to wavelength by ν = c/λ.
- Velocity (c): Speed of the wave; calculated as c = νλ.
- Wave Number: Number of wavelengths per cm.
- Amplitude (a): Height of the wave crest or depth of the trough, indicating intensity.
Electromagnetic Waves
- Radio Waves: Wavelength range of 3×10¹⁴ to 3×10⁷ Å.
- Microwaves: Wavelength range of 3×10⁹ to 3×10⁶ Å.
- Infrared (IR): Wavelength range of 6×10⁶ to 7600 Å.
- Visible Light: Wavelength range of 7600 to 3800 Å.
- Ultraviolet (UV): Wavelength range of 3800 to 150 Å.
- X-rays: Wavelength range of 150 to 0.1 Å.
- Gamma Rays: Wavelength range of 0.1 to 0.01 Å.
Atomic Spectrum of Hydrogen Atom
- Rydberg constant (RH) is 108978 cm⁻¹.
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Spectral Series:
- Lyman: n₁=1, n₂=2,3,4... (UV region).
- Balmer: n₁=2, n₂=3,4,5... (Visible region).
- Paschen: n₁=3, n₂=4,5,6... (IR region).
- Brackett: n₁=4, n₂=5,6,7... (IR region).
- Pfund: n₁=5, n₂=6,7,8... (IR region).
Photoelectric Effect
- Ejection of electrons from metal surfaces occurs when light of suitable frequency strikes.
- The minimum frequency required for ejection is the threshold frequency (vo).
- Ejected electron energy is proportional to light frequency; number of ejected electrons depends on light intensity.
Planck’s Quantum Theory
- Energy is emitted or absorbed in packets called quanta (photons for light).
- The energy of each quantum is E = hν; Planck’s constant (h) is 6.626 × 10⁻³⁴ J sec.
- Energy absorption is quantized in integer multiples of hν.
Bohr’s Atomic Model
- Electrons orbit the nucleus in paths with fixed energy levels.
- Angular momentum (mvr) is quantized, being an integer multiple of h/2π.
- Energy jumps between levels involve electromagnetic radiation (E = hν).
- Hydrogen atom energy levels are expressed as En = -RH (1/n²).
- For hydrogen-like species, radius (rn) and energy (En) for nth orbit are calculated by rn = 52.9 × n²/Z pm and En = -2.18×10⁻¹⁸(Z²/n²) eV, respectively.
Studying That Suits You
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Description
Revise the fundamental concepts of atomic structure with this quiz tailored for IIT JEE preparation. Explore subatomic particles, their properties, and historical atomic models. Perfect for students looking to strengthen their understanding of chemistry fundamentals.
