Alkali and alkaline earth metals impart colours when heated over burner. It is due to______________?
Correct answer: C. De-excitation of electrons from higher energy levels to low energy level
- A. Smaller electronegativity of alkali metals
- B. Smaller ionic radius of these metals
- C. De-excitation of electrons from higher energy levels to low energy level
- D. Excitation of electrons from low energy levels to higher energy levels
Explanation
Heat excites electrons in metal atoms to higher energy levels, and the characteristic colour appears when those electrons return to lower levels and emit photons. The emitted photon energy, and hence its colour, depends on the energy difference between the levels. Students may choose excitation alone, but excitation absorbs energy and the visible light is produced during de-excitation.
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Electronic configuration describes how electrons occupy shells, subshells and orbitals around an atom. Questions use the Aufbau principle, Pauli exclusion principle and Hund's rule to write configurations, identify valence electrons, form ions and explain periodic trends, including common exceptions such as chromium and copper.
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