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Line spectra to identify elements (Part - 9) - Atoms Video Lecture - Class 12

FAQs on Line spectra to identify elements (Part - 9) - Atoms Video Lecture - Class 12

1. What is line spectra and how is it used to identify elements?
Ans. Line spectra refers to the unique pattern of colored lines produced when an element is subjected to a high-energy source, such as a flame or an electric discharge. Each element has its own specific set of lines in its line spectra, which acts as a "fingerprint" for that element. By comparing the observed line spectra of an unknown substance with the known line spectra of different elements, scientists can identify the elements present.
2. How are line spectra produced?
Ans. Line spectra are produced when atoms or ions absorb energy and transition from their ground state to an excited state. This excitation can be achieved by subjecting the element to high temperatures, such as heating it in a flame or passing an electric current through a gas discharge tube. When the excited atoms or ions return to their ground state, they release the excess energy in the form of light. This light is then passed through a prism or a diffraction grating, which separates it into its component wavelengths, resulting in the observation of a line spectra.
3. Why do different elements have different line spectra?
Ans. Different elements have different line spectra because each element has a unique arrangement of electrons in its atom or ion. When energy is absorbed by an element, the electrons in its atom or ion are excited to higher energy levels. However, these electrons can only occupy specific energy levels, known as discrete energy levels. When the excited electrons return to their original energy level, they release energy in the form of light. The energy released corresponds to the difference in energy between the excited state and the ground state, and this energy difference determines the wavelength of light emitted. Since each element has a different electron configuration, the energy differences and consequently the wavelengths of light emitted are unique to each element, resulting in different line spectra.
4. How can line spectra be used to identify elements in practice?
Ans. Line spectra can be used to identify elements in practice by comparing the observed line spectra of an unknown substance with the known line spectra of different elements. This comparison can be done visually, by matching the pattern of lines in the unknown line spectra with the pattern of lines in the known line spectra. Additionally, the wavelengths of the lines in the unknown line spectra can be measured using spectroscopic techniques, and these wavelengths can be compared with the wavelengths of known lines for different elements. By finding a match between the observed wavelengths and the known wavelengths, the element present in the unknown substance can be identified.
5. Can line spectra be used to identify elements in compounds or mixtures?
Ans. Yes, line spectra can be used to identify elements in compounds or mixtures. When a compound or mixture is subjected to high-energy sources, the individual elements present in the compound or mixture will emit their characteristic line spectra. By analyzing the line spectra, scientists can identify the elements present in the compound or mixture. However, it is important to note that the line spectra of a compound or mixture will be a combination of the line spectra of its individual elements, making the analysis more complex.
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