- Understand the historical development of atomic theory.
- Explain the significance of J. J. Thomson's experiments in the context of atomic structure.
- Describe the differences between Thomson's and Rutherford's models of the atom.
- Analyze the limitations of Rutherford's model in explaining atomic stability and spectra.
- Summarize Bohr's model of the hydrogen atom and its postulates.
- Apply Bohr's quantization condition to calculate energy levels and transitions in hydrogenic atoms.
- Discuss the implications of de Broglie's hypothesis on the wave nature of electrons.
- Evaluate the applicability of Bohr's model to multi-electron atoms and its limitations.
Atoms
CBSE Learning Objectives – Key Concepts & Skills You Must Know
CBSE Revision Notes & Quick Summary for Last-Minute Study
Chapter Twelve: Atoms
12.1 Introduction
- By the nineteenth century, evidence supported the atomic hypothesis of matter.
- In 1897, J. J. Thomson discovered that atoms contain negatively charged electrons, making them electrically neutral overall.
- Thomson's model (1898): Positive charge is uniformly distributed, with electrons embedded like seeds in a watermelon (plum pudding model).
- Subsequent studies revealed a different arrangement of charges.
12.2 Key Models of the Atom
Thomson's Model
- Atom as a spherical cloud of positive charges with electrons embedded.
Rutherford's Model
- Most mass and positive charge concentrated in a tiny nucleus.
- Electrons revolve around the nucleus.
- Issues with Rutherford's model:
- Predicts instability due to spiraling electrons.
- Cannot explain characteristic line spectra of different elements.
Bohr's Model
- Proposed to explain line spectra and stability of hydrogenic atoms.
- Introduced three postulates:
- Electrons revolve in stable orbits without emitting energy.
- Angular momentum is quantized: L = nh/2Ï€ (n = principal quantum number).
- Electrons can transition between orbits, emitting or absorbing photons.
- Total energy quantized: Eₙ = -13.6 eV/n².
- Ground state energy of hydrogen atom is -13.6 eV.
12.3 De Broglie's Explanation
- De Broglie proposed that electrons have wave properties, explaining Bohr's quantization of angular momentum.
- Standing waves form in electron orbits, leading to quantized energy levels.
12.4 Limitations of Bohr's Model
- Applicable only to hydrogenic atoms; fails for multi-electron atoms.
- Cannot explain relative intensities of spectral lines.
12.5 Summary of Key Points
- Atoms are electrically neutral, containing equal positive and negative charges.
- Thomson's model depicts a cloud of positive charge with embedded electrons.
- Rutherford's model has a nucleus with electrons revolving around it.
- Bohr's model introduces quantized orbits and energy levels for hydrogenic atoms.
- The wave nature of electrons explains quantization in Bohr's model.
- Bohr's model has limitations and is replaced by quantum mechanics for complex atoms.
CBSE Exam Tips, Important Questions & Common Mistakes to Avoid
Common Mistakes and Exam Tips
Common Pitfalls
- Misunderstanding Atomic Models: Students often confuse the characteristics of Thomson's and Rutherford's models. Remember that Thomson's model depicts a uniform distribution of positive charge with electrons embedded, while Rutherford's model has a dense nucleus with electrons orbiting around it.
- Ignoring Stability Issues: Many overlook the instability predicted by both Thomson's and Rutherford's models. Thomson's model is electrostatically unstable, and Rutherford's model predicts that electrons should spiral into the nucleus due to electromagnetic radiation.
- Confusing Quantum Numbers: Be careful not to confuse the principal quantum number (n) with other quantum numbers. Only the principal quantum number determines the energy levels in Bohr's model.
Exam Tips
- Focus on Key Postulates: When studying Bohr's model, emphasize the three postulates: stable orbits without energy emission, quantized angular momentum, and energy transitions leading to photon emission.
- Understand Energy Levels: Be clear on how energy levels are quantized in hydrogen atoms, specifically that the ground state energy is -13.6 eV and how higher states correspond to larger values of n.
- Practice Problems: Work through problems involving energy transitions and spectral lines, as these are common exam questions. Familiarize yourself with calculations involving the frequency and wavelength of emitted photons during transitions.
CBSE Quiz & Practice Test – MCQs, True/False Questions with Solutions
Multiple Choice Questions
A.
Discovered the electron
B.
Proposed the nuclear model
C.
Developed a formula for hydrogen spectral lines
D.
Identified alpha and beta rays
Correct Answer: C
Solution:
Johann Jakob Balmer developed a simple empirical formula for the wavelengths of a group of lines emitted by atomic hydrogen.
A.
Electron
B.
Neutron
C.
Nucleus
D.
Photon
Correct Answer: C
Solution:
Ernst Rutherford's experiments on alpha-particle scattering led to the discovery of the atomic nucleus.
A.
The positive charge is concentrated in the nucleus, with electrons orbiting around it.
B.
Electrons are embedded in a positively charged sphere, similar to seeds in a watermelon.
C.
Atoms consist of a dense nucleus with electrons in fixed orbits.
D.
Electrons move in elliptical orbits around a central positive charge.
Correct Answer: B
Solution:
J. J. Thomson's plum pudding model describes the atom as a positively charged sphere with electrons embedded within it, similar to seeds in a watermelon.
A.
Lyman series
B.
Balmer series
C.
Paschen series
D.
Brackett series
Correct Answer: C
Solution:
The Paschen series of the hydrogen emission spectrum is visible in the infrared region.
A.
Lyman series
B.
Balmer series
C.
Paschen series
D.
Brackett series
Correct Answer: B
Solution:
The Balmer series corresponds to electron transitions that end at the second energy level in the hydrogen atom.
A.
It did not account for the presence of electrons
B.
It suggested a continuous spectrum instead of discrete wavelengths
C.
It incorrectly described the nucleus as positively charged
D.
It was based on incorrect experimental data
Correct Answer: B
Solution:
Rutherford's model could not explain why atoms emit light of only discrete wavelengths, as it suggested a continuous spectrum due to the classical picture of electrons revolving around the nucleus.
A.
Lyman series
B.
Balmer series
C.
Paschen series
D.
Rydberg series
Correct Answer: B
Solution:
The Balmer series is part of the hydrogen emission spectrum and is visible in the visible spectrum.
A.
The atoms in rarefied gases are isolated, leading to emission at specific wavelengths.
B.
Rarefied gases have high atomic density, causing continuous spectra.
C.
The interaction between atoms in rarefied gases causes discrete wavelengths.
D.
Rarefied gases absorb light at all wavelengths, emitting discrete ones.
Correct Answer: A
Solution:
In rarefied gases, the average spacing between atoms is large, so the radiation emitted can be considered due to individual atoms rather than interactions between atoms or molecules. This results in emission at discrete wavelengths.
A.
Lyman series
B.
Balmer series
C.
Paschen series
D.
Brackett series
Correct Answer: B
Solution:
The Balmer series corresponds to electron transitions in hydrogen that emit light in the visible region of the electromagnetic spectrum.
A.
Scattering of alpha particles by metal foils
B.
Electric discharge through gases
C.
Discovery of radioactivity
D.
Measurement of atomic spectra
Correct Answer: A
Solution:
Rutherford's nuclear model was proposed based on the results of the alpha-particle scattering experiment performed by Hans Geiger and Ernst Marsden under Rutherford's guidance.
A.
Balmer series
B.
Lyman series
C.
Paschen series
D.
Rydberg series
Correct Answer: B
Solution:
The Lyman series is found in the ultraviolet region of the hydrogen spectrum.
A.
Lyman series
B.
Balmer series
C.
Paschen series
D.
Brackett series
Correct Answer: B
Solution:
The Balmer series is associated with the visible region of the electromagnetic spectrum, as indicated by the wavelengths such as 365 nm and 656 nm.
A.
The discovery of electron charge
B.
The scattering of alpha particles by metal foils
C.
The observation of spectral lines
D.
The discovery of isotopes
Correct Answer: B
Solution:
Rutherford's nuclear model was proposed based on the experimental evidence from the scattering of alpha particles by metal foils, which indicated a concentrated positive charge in the nucleus.
A.
Plum pudding model
B.
Nuclear model
C.
Planetary model
D.
Quantum model
Correct Answer: A
Solution:
J. J. Thomson proposed the plum pudding model, where electrons are embedded in a positively charged 'pudding'.
A.
It could not explain the stability of the atom.
B.
It could not account for the existence of isotopes.
C.
It failed to explain the discrete wavelengths of spectral lines.
D.
It did not consider the electron's wave nature.
Correct Answer: C
Solution:
Rutherford's nuclear model could not explain why atoms emit light of only discrete wavelengths, a limitation that was later addressed by quantum mechanics.
A.
Ernst Rutherford
B.
Niels Bohr
C.
J. J. Thomson
D.
Albert Einstein
Correct Answer: C
Solution:
J. J. Thomson proposed the plum pudding model of the atom in 1898.
A.
J. J. Thomson
B.
Ernst Rutherford
C.
Niels Bohr
D.
James Chadwick
Correct Answer: A
Solution:
J. J. Thomson proposed the plum pudding model of the atom in 1898, where the positive charge is uniformly distributed, and electrons are embedded like seeds in a watermelon.
A.
The continuous motion of electrons around the nucleus
B.
The quantized energy levels of electrons
C.
The uniform distribution of positive charge
D.
The interaction between atoms in a dense gas
Correct Answer: B
Solution:
Rutherford's model could not explain discrete wavelengths, but later models showed that the quantized energy levels of electrons are responsible for discrete spectral lines.
A.
Atoms are indivisible and solid.
B.
Electrons are embedded in a positive sphere.
C.
Atoms have a small, dense nucleus.
D.
Electrons move in fixed paths around the nucleus.
Correct Answer: C
Solution:
The alpha-particle scattering experiment led to the conclusion that atoms have a small, dense nucleus.
A.
J. J. Thomson
B.
Johann Jakob Balmer
C.
Hans Geiger and Ernst Marsden
D.
Niels Bohr
Correct Answer: C
Solution:
Hans Geiger and Ernst Marsden performed the experiment under the suggestion of Ernst Rutherford.
A.
It could not explain the discrete wavelengths of light emitted by atoms.
B.
It did not account for the electron's charge.
C.
It suggested that atoms were indivisible.
D.
It proposed that electrons were stationary.
Correct Answer: A
Solution:
Rutherford's nuclear model could not explain why atoms emit light at only certain discrete wavelengths, which was a significant limitation.
A.
Balmer series
B.
Paschen series
C.
Lyman series
D.
Brackett series
Correct Answer: C
Solution:
The Lyman series is associated with the ultraviolet region, as indicated by the wavelengths 91 nm and 122 nm.
A.
Rutherford's nuclear model
B.
Bohr's model
C.
Thomson's plum pudding model
D.
Quantum mechanical model
Correct Answer: C
Solution:
J. J. Thomson proposed the plum pudding model in 1898, where he suggested that electrons are embedded within a positively charged sphere.
A.
Continuous spectrum
B.
Discrete wavelengths
C.
Infrared radiation
D.
Ultraviolet radiation
Correct Answer: B
Solution:
Rarefied gases emit radiation at discrete wavelengths, appearing as a series of bright lines, when excited electrically.
A.
Atoms are indivisible particles.
B.
Electrons orbit the nucleus in fixed paths.
C.
The atom's positive charge is concentrated in a small nucleus.
D.
Electrons are embedded in a positive sphere.
Correct Answer: C
Solution:
Rutherford's gold foil experiment led to the conclusion that the positive charge and most of the atom's mass are concentrated in a small nucleus.
A.
The Lyman series is visible in the visible spectrum.
B.
The Balmer series is found in the ultraviolet region.
C.
The Paschen series corresponds to the infrared region.
D.
The Brackett series is visible in the ultraviolet region.
Correct Answer: C
Solution:
The Paschen series corresponds to the infrared region, while the Lyman series is in the ultraviolet and the Balmer series is in the visible spectrum.
A.
Atoms contain a dense nucleus
B.
Atoms have negatively charged constituents called electrons
C.
Atoms are indivisible particles
D.
Atoms emit continuous spectra
Correct Answer: B
Solution:
J. J. Thomson's experiments revealed that atoms contain negatively charged constituents, known as electrons, which are identical for all atoms.
A.
Dense gases emit a continuous spectrum, while rarefied gases emit discrete spectral lines.
B.
Both dense and rarefied gases emit continuous spectra.
C.
Dense gases emit discrete spectral lines, while rarefied gases emit a continuous spectrum.
D.
Both dense and rarefied gases emit discrete spectral lines.
Correct Answer: A
Solution:
Dense gases emit a continuous spectrum due to interactions between atoms or molecules, whereas rarefied gases emit discrete spectral lines due to individual atomic emissions.
A.
Mass and positive charge are uniformly distributed throughout the atom.
B.
Mass is concentrated in the nucleus, while electrons revolve around it.
C.
Electrons are stationary within a positively charged sphere.
D.
Mass is evenly distributed between electrons and the nucleus.
Correct Answer: B
Solution:
Rutherford's model posits that the entire positive charge and most of the mass of the atom are concentrated in a small volume called the nucleus, with electrons revolving around it.
A.
Thomson's plum pudding model
B.
Rutherford's nuclear model
C.
Bohr's model
D.
Quantum mechanical model
Correct Answer: A
Solution:
Thomson's plum pudding model proposed that the positive charge is spread throughout the atom, with electrons embedded within it, similar to seeds in a watermelon.
A.
Cathode ray tube experiment
B.
Alpha-particle scattering experiment
C.
Oil drop experiment
D.
Photoelectric effect experiment
Correct Answer: B
Solution:
The alpha-particle scattering experiment led to the proposal of Rutherford's nuclear model of the atom.
A.
Plum pudding model
B.
Planetary model
C.
Bohr model
D.
Quantum mechanical model
Correct Answer: A
Solution:
J. J. Thomson proposed the plum pudding model of the atom in 1898, where the positive charge is uniformly distributed and electrons are embedded like seeds in a watermelon.
A.
To confirm the plum pudding model of the atom.
B.
To measure the charge of an electron.
C.
To investigate the atomic structure and discover the nucleus.
D.
To study the emission spectra of hydrogen.
Correct Answer: C
Solution:
The alpha-particle scattering experiment aimed to investigate the atomic structure, leading to the discovery of the nucleus and the proposal of Rutherford's nuclear model of the atom.
A.
J. J. Thomson
B.
Ernst Rutherford
C.
Hans Geiger and Ernst Marsden
D.
Niels Bohr
Correct Answer: C
Solution:
Hans Geiger and Ernst Marsden conducted the experiment under the suggestion of Ernst Rutherford, leading to the discovery of the atomic nucleus.
A.
Plum pudding model
B.
Rutherford model
C.
Bohr model
D.
Quantum mechanical model
Correct Answer: A
Solution:
The plum pudding model, proposed by J. J. Thomson, describes the atom as a sphere of positive charge with electrons embedded in it.
A.
J. J. Thomson
B.
Ernst Rutherford
C.
Niels Bohr
D.
Albert Einstein
Correct Answer: B
Solution:
Ernst Rutherford is credited with the discovery of alpha-rays and beta-rays.
A.
Continuous spectrum
B.
Discrete wavelengths
C.
Infrared radiation
D.
Ultraviolet radiation
Correct Answer: B
Solution:
Rarefied gases emit light with discrete wavelengths, appearing as a series of bright lines.
A.
Atoms contain a nucleus.
B.
Atoms contain negatively charged electrons.
C.
Atoms emit a continuous spectrum.
D.
Atoms are indivisible.
Correct Answer: B
Solution:
J. J. Thomson's experiments revealed that atoms contain negatively charged constituents called electrons.
A.
Electrons are embedded in a positively charged sphere.
B.
Electrons orbit the nucleus like planets around the sun.
C.
Electrons are located in fixed orbits with quantized energy levels.
D.
Electrons are randomly distributed outside the nucleus.
Correct Answer: A
Solution:
In J. J. Thomson's model, the atom is described as a positively charged sphere with electrons embedded within it, similar to seeds in a watermelon.
A.
Electrons orbit the nucleus like planets around the sun.
B.
Electrons are embedded in a uniform sphere of positive charge.
C.
Electrons are located in distinct energy levels.
D.
Electrons are concentrated in the nucleus.
Correct Answer: B
Solution:
In J. J. Thomson's plum pudding model, electrons are embedded in a uniform sphere of positive charge, similar to seeds in a watermelon.
A.
Mass is evenly distributed throughout the atom.
B.
Mass is concentrated in the electrons.
C.
Mass is concentrated in the nucleus.
D.
Mass is concentrated in the electron cloud.
Correct Answer: C
Solution:
Rutherford's model suggests that most of the atom's mass is concentrated in a small volume called the nucleus.
A.
It is in the ultraviolet region.
B.
It is in the visible spectrum.
C.
It is in the infrared region.
D.
It corresponds to X-ray emissions.
Correct Answer: B
Solution:
The Balmer series is associated with the visible spectrum of hydrogen.
A.
The discovery of the neutron.
B.
The observation of discrete spectral lines in hydrogen.
C.
The scattering of alpha particles by a thin gold foil.
D.
The discovery of isotopes.
Correct Answer: C
Solution:
The scattering of alpha particles by a thin gold foil, as observed by Geiger and Marsden, led to the rejection of Thomson's plum pudding model and the development of Rutherford's nuclear model.
A.
J. J. Thomson
B.
Niels Bohr
C.
Ernst Rutherford
D.
Albert Einstein
Correct Answer: C
Solution:
Ernst Rutherford proposed the classic experiment of scattering alpha particles, which led to the discovery of the atomic nucleus.
A.
Evenly distributed throughout the atom
B.
In the electrons
C.
In the nucleus
D.
In the outer shells
Correct Answer: C
Solution:
In Rutherford's nuclear model, most of the atom's mass is concentrated in the nucleus.
A.
Lyman series
B.
Balmer series
C.
Paschen series
D.
Brackett series
Correct Answer: C
Solution:
The Paschen series corresponds to the infrared region, as indicated by the wavelengths associated with it.
A.
Lyman series
B.
Balmer series
C.
Paschen series
D.
Brackett series
Correct Answer: B
Solution:
The Balmer series is associated with the visible spectrum for hydrogen.
A.
Electrons are embedded in a positively charged sphere.
B.
Electrons orbit around a central nucleus.
C.
Electrons are scattered randomly around the atom.
D.
Electrons are fixed at specific energy levels.
Correct Answer: A
Solution:
The plum pudding model suggests that electrons are embedded in a positively charged sphere, similar to seeds in a watermelon.
A.
Lyman series
B.
Balmer series
C.
Paschen series
D.
Brackett series
Correct Answer: C
Solution:
The Paschen series corresponds to the infrared region in the emission spectrum of hydrogen.
A.
Balmer series
B.
Lyman series
C.
Paschen series
D.
Brackett series
Correct Answer: B
Solution:
The Lyman series corresponds to the ultraviolet region of the hydrogen emission spectrum.
A.
Lyman series
B.
Balmer series
C.
Paschen series
D.
Brackett series
Correct Answer: B
Solution:
The Balmer series is visible in the visible spectrum, as indicated by the labeled wavelengths of 365 nm and 656 nm in the diagram.
A.
Transition from to
B.
Transition from to
C.
Transition from to
D.
Transition from to
Correct Answer: B
Solution:
The transition from to corresponds to the Lyman series, which is in the ultraviolet region.
A.
Positive charge is uniformly distributed throughout the atom, with electrons embedded like seeds in a watermelon.
B.
Electrons orbit a central positive nucleus, similar to planets orbiting the sun.
C.
Electrons are concentrated at the center, with positive charge surrounding them.
D.
Positive and negative charges are separated by a fixed distance within the atom.
Correct Answer: A
Solution:
In J. J. Thomson's plum pudding model, the positive charge is uniformly distributed throughout the atom, and electrons are embedded within it, similar to seeds in a watermelon.
A.
Lyman series
B.
Balmer series
C.
Paschen series
D.
Brackett series
Correct Answer: B
Solution:
The Balmer series corresponds to the visible spectrum, with wavelengths such as 365 nm and 656 nm.
A.
Balmer series
B.
Paschen series
C.
Lyman series
D.
Brackett series
Correct Answer: C
Solution:
The Lyman series corresponds to the ultraviolet region in the hydrogen emission spectrum.
A.
Balmer series
B.
Paschen series
C.
Lyman series
D.
Brackett series
Correct Answer: C
Solution:
The Lyman series of the hydrogen emission spectrum is visible in the ultraviolet region, as indicated by wavelengths such as 91 nm and 122 nm.
A.
Thomson's cathode ray experiment
B.
Rutherford's alpha-particle scattering experiment
C.
Bohr's hydrogen spectrum experiment
D.
Einstein's photoelectric effect experiment
Correct Answer: B
Solution:
Rutherford's alpha-particle scattering experiment led to the discovery of the atomic nucleus.
A.
The existence of electrons
B.
The discrete wavelengths of light emitted by atoms
C.
The presence of protons
D.
The mass of the atom
Correct Answer: B
Solution:
Rutherford's model could not explain why atoms emit light of only discrete wavelengths.
A.
Lyman series
B.
Balmer series
C.
Paschen series
D.
Brackett series
Correct Answer: B
Solution:
The Balmer series is associated with the visible spectrum.
A.
Continuous spectrum
B.
Discrete spectrum
C.
Absorption spectrum
D.
Blackbody spectrum
Correct Answer: B
Solution:
Rarefied gases emit a discrete spectrum of bright lines when excited electrically.
A.
The cathode ray tube experiment.
B.
The gold foil experiment.
C.
The oil drop experiment.
D.
The photoelectric effect experiment.
Correct Answer: B
Solution:
The gold foil experiment, conducted by Geiger and Marsden under Rutherford's guidance, led to the discovery of the atomic nucleus.
A.
Ernst Rutherford
B.
Johann Jakob Balmer
C.
J. J. Thomson
D.
Niels Bohr
Correct Answer: B
Solution:
Johann Jakob Balmer obtained a simple empirical formula for the wavelengths of lines emitted by atomic hydrogen, known as the Balmer series.
A.
To discover electrons
B.
To investigate the atomic structure
C.
To measure the speed of light
D.
To study electromagnetic waves
Correct Answer: B
Solution:
The alpha-particle scattering experiment by Geiger and Marsden aimed to investigate the atomic structure, leading to the proposal of Rutherford's nuclear model.
A.
656 nm
B.
820 nm
C.
91 nm
D.
1875 nm
Correct Answer: C
Solution:
The Lyman series includes wavelengths such as 91 nm, which are in the ultraviolet region.
A.
Atoms are mostly empty space with a dense nucleus.
B.
Electrons are evenly distributed throughout the atom.
C.
Atoms consist of a solid positive sphere.
D.
Electrons are stationary within the atom.
Correct Answer: A
Solution:
Rutherford's experiment concluded that atoms are mostly empty space with a dense nucleus at the center.
A.
Discovery of the electron
B.
Discovery of the atomic nucleus
C.
Discovery of the neutron
D.
Discovery of isotopes
Correct Answer: B
Solution:
Geiger and Marsden's experiments led to the discovery of the atomic nucleus, as they observed that a small fraction of alpha particles were deflected at large angles, indicating a concentrated positive charge.
A.
Continuous spectrum
B.
Discrete wavelengths
C.
Infrared spectrum
D.
Ultraviolet spectrum
Correct Answer: B
Solution:
Light emitted from rarefied gases when excited electrically has only certain discrete wavelengths.
A.
Continuous spectrum
B.
Discrete wavelengths
C.
Higher intensity
D.
Lower frequency
Correct Answer: B
Solution:
Light emitted by rarefied gases has discrete wavelengths, appearing as a series of bright lines, unlike the continuous spectrum of dense gases.
A.
They indicate the presence of isotopes.
B.
They are due to interactions between atoms.
C.
They are characteristic of individual atoms.
D.
They result from thermal vibrations.
Correct Answer: C
Solution:
Discrete wavelengths in the emission spectra of rarefied gases are characteristic of individual atoms, as the average spacing between atoms is large, minimizing interactions.
A.
In the electron cloud surrounding the nucleus.
B.
Uniformly distributed throughout the atom.
C.
In the nucleus at the center of the atom.
D.
In the outer orbits of the atom.
Correct Answer: C
Solution:
Rutherford's nuclear model states that the majority of the atom's mass is concentrated in the nucleus at the center of the atom.
A.
J. J. Thomson
B.
Ernst Rutherford
C.
Johann Jakob Balmer
D.
Hans Geiger
Correct Answer: A
Solution:
J. J. Thomson's experiments on electric discharge through gases revealed the presence of electrons in atoms.
A.
The wavelengths of the Balmer series fall within the range of visible light.
B.
The Balmer series involves transitions to the ground state.
C.
The Balmer series is emitted by rarefied gases under high pressure.
D.
The Balmer series is the result of electron transitions from the first excited state.
Correct Answer: A
Solution:
The Balmer series is visible because its wavelengths fall within the range of visible light, as indicated by the specific wavelengths such as 365 nm and 656 nm.
A.
J. J. Thomson
B.
Niels Bohr
C.
Ernst Rutherford
D.
Albert Einstein
Correct Answer: C
Solution:
Ernst Rutherford is credited with discovering the atomic nucleus through his alpha particle scattering experiments.
A.
Lyman series
B.
Balmer series
C.
Paschen series
D.
Brackett series
Correct Answer: B
Solution:
The Balmer series corresponds to the visible region of the hydrogen emission spectrum.
A.
The positive charge is uniformly distributed throughout the atom.
B.
The positive charge and most of the mass are concentrated in a small nucleus.
C.
Electrons are embedded in a sphere of positive charge.
D.
Electrons revolve around the nucleus in fixed orbits without any energy loss.
Correct Answer: B
Solution:
Rutherford's nuclear model proposed that the positive charge and most of the mass of the atom are concentrated in a small region called the nucleus, with electrons revolving around it.
A.
Lyman series
B.
Balmer series
C.
Paschen series
D.
Brackett series
Correct Answer: C
Solution:
The Paschen series corresponds to the infrared region of the hydrogen spectrum.
A.
It is visible in the infrared region.
B.
It is visible in the ultraviolet region.
C.
It is visible in the visible spectrum.
D.
It is visible in the X-ray region.
Correct Answer: C
Solution:
The Balmer series is visible in the visible spectrum, as indicated by wavelengths such as 365 nm and 656 nm.
A.
It is visible in the ultraviolet region.
B.
It is associated with the infrared region.
C.
It is visible in the visible spectrum.
D.
It is not associated with any specific region.
Correct Answer: C
Solution:
The Balmer series is visible in the visible spectrum, as indicated by the specific wavelengths associated with it.
True or False
Correct Answer: True
Solution:
According to J. J. Thomson's plum pudding model, the positive charge is spread uniformly throughout the atom, with electrons embedded like seeds in a watermelon.
Correct Answer: False
Solution:
The Balmer series is visible in the visible spectrum, not the ultraviolet region.
Correct Answer: False
Solution:
The Lyman series is located in the ultraviolet region of the spectrum.
Correct Answer: True
Solution:
Rutherford's nuclear model proposed that electrons revolve around a central nucleus, much like planets orbit the sun.
Correct Answer: False
Solution:
In rarefied gases, the light emitted appears as a series of bright lines, not a continuous spectrum.
Correct Answer: True
Solution:
The Lyman series of hydrogen's emission spectrum is indeed observed in the ultraviolet region.
Correct Answer: True
Solution:
J. J. Thomson's experiments on electric discharge through gases showed that atoms contain negatively charged electrons that are identical for all atoms.
Correct Answer: False
Solution:
The emission spectrum of rarefied gases heated in a flame consists of discrete wavelengths, appearing as a series of bright lines.
Correct Answer: False
Solution:
Rutherford's nuclear model could not explain the emission of light in discrete wavelengths, which was a limitation of the model.
Correct Answer: False
Solution:
The Balmer series of hydrogen is located in the visible spectrum, not the infrared region.
Correct Answer: True
Solution:
Rutherford's model suggested that electrons revolve around a central nucleus, similar to planets orbiting the sun.
Correct Answer: True
Solution:
The scattering experiments conducted by Geiger and Marsden under Rutherford's guidance led to the discovery of the atomic nucleus.
Correct Answer: True
Solution:
Rutherford's nuclear model proposes that the entire positive charge and most of the mass of the atom is concentrated in the nucleus, with electrons revolving around it.
Correct Answer: False
Solution:
J. J. Thomson's model, known as the plum pudding model, proposed that the positive charge is uniformly distributed throughout the atom, not concentrated in the nucleus.
Correct Answer: True
Solution:
J. J. Thomson's plum pudding model depicted the atom as having electrons embedded like seeds in a watermelon within a positively charged 'pudding'.
Correct Answer: True
Solution:
In rarefied gases, the average spacing between atoms is large, allowing individual atoms to emit radiation, resulting in discrete bright lines.
Correct Answer: True
Solution:
According to J. J. Thomson's model, the positive charge of the atom is uniformly distributed throughout the volume of the atom, with electrons embedded in it.
Correct Answer: True
Solution:
It was established that each element has a unique spectrum of radiation, which is characteristic of that element.
Correct Answer: True
Solution:
Rutherford discovered the atomic nucleus by analyzing the results of alpha-particle scattering experiments.
Correct Answer: True
Solution:
The Paschen series is part of hydrogen's emission spectrum and is observed in the infrared region.
Correct Answer: False
Solution:
In the plum pudding model, the positive charge is uniformly distributed throughout the volume of the atom, not concentrated in a nucleus.
Correct Answer: True
Solution:
J. J. Thomson discovered electrons as negatively charged constituents of atoms through his experiments with electric discharge in gases.
Correct Answer: True
Solution:
It was established in the early nineteenth century that each element has a characteristic spectrum of radiation.
Correct Answer: False
Solution:
In the plum pudding model, the positive charge is uniformly distributed throughout the atom, not concentrated in a nucleus.
Correct Answer: False
Solution:
Light emitted from rarefied gases consists of discrete wavelengths, appearing as a series of bright lines.
Correct Answer: True
Solution:
In rarefied gases, the average spacing between atoms is large, leading to the emission of light at discrete wavelengths, appearing as bright lines.
Correct Answer: True
Solution:
Rutherford's experiments with alpha-particle scattering led to the discovery of the atomic nucleus, where he proposed that the positive charge and most of the mass of the atom are concentrated.
Correct Answer: True
Solution:
Rutherford's model describes electrons orbiting the nucleus in a manner analogous to planets orbiting the sun.
Correct Answer: True
Solution:
Rarefied gases emit light at certain discrete wavelengths, resulting in a spectrum that appears as a series of bright lines.
Correct Answer: True
Solution:
Each element has a characteristic spectrum of radiation, with hydrogen always giving a set of lines with fixed relative positions.
Correct Answer: True
Solution:
J. J. Thomson's experiments on electric discharge through gases revealed that all atoms contain identical negatively charged constituents known as electrons.
Correct Answer: True
Solution:
Rutherford's model failed to explain the discrete wavelengths of light emitted by atoms, which was a limitation of the model.
Correct Answer: True
Solution:
J. J. Thomson's experiments on electric discharge through gases showed that atoms of different elements contain electrons, which are negatively charged.
Correct Answer: True
Solution:
In 1885, Johann Jakob Balmer obtained a simple empirical formula that gave the wavelengths of a group of lines emitted by atomic hydrogen.
Correct Answer: False
Solution:
The Paschen series is associated with the infrared region, not the ultraviolet region.
Correct Answer: True
Solution:
Rutherford's alpha-particle scattering experiments led to the discovery of the atomic nucleus.
Correct Answer: False
Solution:
Light emitted from rarefied gases appears as a series of bright lines, not a continuous spectrum.
Correct Answer: False
Solution:
J. J. Thomson's plum pudding model proposed that the positive charge is uniformly distributed throughout the atom, not concentrated in a nucleus.
Correct Answer: False
Solution:
Rutherford's nuclear model proposed that the entire positive charge and most of the mass of the atom are concentrated in a small volume called the nucleus.
Correct Answer: False
Solution:
The Lyman series is positioned in the ultraviolet region, not the infrared region.
Correct Answer: True
Solution:
Rutherford's experiments with alpha-particle scattering led to the discovery of the atomic nucleus.
Correct Answer: True
Solution:
Light emitted from rarefied gases has discrete wavelengths, appearing as a series of bright lines due to individual atoms.
Correct Answer: True
Solution:
Rutherford's experiments, particularly the scattering of alpha particles, led to the discovery of the atomic nucleus.
Correct Answer: True
Solution:
Rarefied gases emit light at discrete wavelengths, resulting in a spectrum of bright lines, unlike the continuous spectrum from condensed matter.
Correct Answer: True
Solution:
In rarefied gases, the average spacing between atoms is large, so the radiation emitted can be considered due to individual atoms.
Correct Answer: False
Solution:
The Balmer series is visible in the visible spectrum, not the ultraviolet region.
Correct Answer: False
Solution:
In J. J. Thomson's plum pudding model, the positive charge is uniformly distributed throughout the atom, not concentrated in a nucleus.
Correct Answer: True
Solution:
Rutherford's model proposed that the atom's positive charge and most of its mass are concentrated in a small central nucleus, with electrons orbiting around it.
Correct Answer: False
Solution:
Rutherford's nuclear model could not explain why atoms emit light of only discrete wavelengths.
Correct Answer: False
Solution:
Light emitted from rarefied gases heated in a flame has only certain discrete wavelengths, appearing as a series of bright lines.