Cupric chloride produces a green colour flame while strontium chloride produces a crimson red flame.
• Do you observe yellow light in street lamps? Sodium vapours produce yellow light in street lamps. • Why do different elements emit different flame colours when heated by the same non-luminous flame? Scientists found that each element emits its own characteristic colour. These colours correspond to certain discrete wavelengths of light and are called line spectra. The lines in atomic spectra can be used to identify unknown atoms, just like fingerprints are used to identify peopleexamine the spectrum of hydrogen atom. • What does a line spectrum tell us about the structure of an atom? Niels Bohr proposed that electrons in an atom occupy ‘stationary’ orbits (states) of fixed energy at different distances from the nucleus.
When an electron ‘jumps’ from a lower energy state (ground state) to higher energy states (excited state) it absorbs energy or emits energy when such a jump occurs from a higher energy state to a lower energy state. The energies of an electron in an atom can have only certain values E1 , E2