Answer to Question #149548 in General Chemistry for happy

Question

Which do you think is hotter, a red star or a blue star? Explain it using the concept found in Electronic structure.

Answer 1

The surface temperature of a star determines the color of light it emits. Blue stars are hotter than red stars.

When enough energy is supplied (higher temperature or higher voltage), Ca will give up one of its 4s² valence electrons to become Ca⁺, with a 4s¹ electron structure, and this univalent ion then behaves like a univalent alkali element and emits doublet spectra. Because of the higher energy absorbed, the spectral lines are shifted to shorter wavelengths, causing the Ca⁺ doublet to appear in the violet region of the visible spectrum. The appearance of the Ca⁺ ion doublet in stellar spectra has been used to measure stellar temperatures. Low temperature red stars contain only Ca atom spectra (singlets and triplets) and CaO band and molecular spectra; higher temperature stars, such as the sun, show weak lines of the Ca⁺ ion doublet; and high temperature blue stars emit intense doublet spectra of Ca⁺.