This set of Physical Chemistry Multiple Choice Questions & Answers (MCQs) focuses on “Atomic Spectra and Selection Rules”.
1. What is meant by the atomic spectra?
a) Series of colored lines with dark spaces in between
b) Series of white lines with no spaces in between
c) Series of dark lines with white spaces in between
d) Series of red lines with colored spaces in between
View Answer
Explanation: When atoms are excited, they emit light of certain wavelengths which corresponds to different colors. The emitted light can be observed as a series of colored lines with dark spaces in between them, this series of colored lines is called atomic spectra.
2. What are the main types of atomic spectra?
a) Continuous, absorption
b) Absorption, continuous
c) Emission, absorption
d) Continuous, absorption, emission
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Explanation: The three main types of spectra are continuous, absorption and emission. In continuous spectrum, colors are displayed in visible region. In emission spectrum, electrons move from one energy level to another in discrete steps. Absorption spectrum is used to identify and quantify an atom.
3. Which model of atom signifies the existence of atomic spectra?
a) Rutherford’s model of the atom
b) John Dalton’s model of the atom
c) Plum pudding model of the atom
d) Bohr’s model of the atom
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Explanation: The existence of the atomic spectra is support for Bohr’s model of the atom. It suggests that the atomic spectra of atoms are produced by electrons gaining energy from some source, jumping up to a higher energy level, then immediately drop back to a lower energy level and emitting the energy difference between the two energy levels.
4. Which of the following statements are true?
Statement 1: Ground state means to be in the lowest energy level possible.
Statement 2: Excited state means to be in the highest energy level possible.
a) Statement 1 is true but statement 2 is false
b) Statement 2 is true but statement 1 is false
c) Statement 1 and statement 2, both are true
d) Statement 1 and statement 2, both are false
View Answer
Explanation: When the electrons of an atom are in its lowest energy state, then it means it is in the ground state but when an electron of an atom jumps to a higher state then it means it is in the excited state or in the higher energy level.
5. When an element emits light?
a) When it is exposed to light
b) When it is under some chemical operations
c) When excited electrons of the element return to the ground state
d) When the electrons of the element jump in excited state
View Answer
Explanation: Atomic emission spectra produced when excited electrons return to the ground state. When electrons return to a lower energy level from a higher energy level, they emit energy in the form of light.
6. Which object is used to view the light emitted by the element?
a) White sheet
b) Telescope
c) Microscope
d) Prism
View Answer
Explanation: The light emitted from the excited atoms is usually viewed through prism. When it is viewed through prism, then individual patterns of lines will be produced, these lines are called spectra for a specific wavelength.
7. What happens when light is passed from the hydrogen gas discharged tube through a prism?
a) It splits into three visible lines
b) No visible lines will be there
c) It splits into four visible lines
d) It splits into two visible lines
View Answer
Explanation: When light from a hydrogen gas discharge tube is passed through a prism, the light is split into four visible lines. Each of these spectral lines corresponds to a different electron transition from a higher energy state to a lower energy state.
8. What is meant by discontinuous spectra?
a) That contains smooth wavelengths
b) Has gaps, holes or breaks
c) Emits light in visible range
d) It has no gaps or holes
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Explanation: A discontinuous spectra is spectra that contains gaps, holes, or breaks in terms of wavelengths. Continuous spectrum is a spectrum that neither contains any holes nor any gaps, it is smooth in terms of wavelength.
9. Does visible light is the only kind of electromagnetic radiation emitted?
a) True
b) False
View Answer
Explanation: No, visible light is not the only kind of electromagnetic radiation emitted. More or less energetic transitions can produce ultraviolet and infrared radiations also. Thus, each atom has its own distinct set of energy levels and each atom has its own distinct emission spectrum.
10. Which of the following statements are true?
Statement 1: Atoms emit photons.
Statement 2: Atoms absorb photons.
a) Statement 1 is true but statement 2 is false
b) Statement 2 is true but statement 1 is false
c) Statement 1 and statement 2, both are true
d) Statement 1 and statement 2, both are false
View Answer
Explanation: Atoms do not only emit photons, they also absorb photons. If a photon hits an atom and the energy of the photon is same as the gap between two electron energy levels in the atom, then the electron in the lower energy can absorb the photon and jump to the higher energy level.
Sanfoundry Global Education & Learning Series – Physical Chemistry.
To practice all areas of Physical Chemistry, here is complete set of Multiple Choice Questions and Answers.
