Why do lithium compounds appear red?

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Li, Lithium is the 3rd element in the periodic table with an atomic number of 3, a soft, alkali metal with an inner metallic luster. Under standard conditions it is the lightest metal and the least dense solid element. Belonging to the alkali metal group it intrinsically is very reactive and flammable, which is why it is primarily stored in mineral oil. Contact with air causes oxidation leading to a dull grey to black surface.

Because of its high reactivity it does not appear in the free state naturally, instead move to more energy efficient ionic compounds. Lithium nuclei are on the verge of instability, having some of the lowest binding energies they are prone to disassociate quickly. Lithium also shows diagonal relationship with Magnesium, showing similarities in atomic and ionic radii, as well as some chemical resemblances.

In a flame test, lithium compounds produce a red crimson’ flame. But remarkably changes to silver if burnt strongly. During flame tests due to heating the atoms of the sample are excited, which lends to their electrons moving from the ground state to the higher energy levels or excited state. As they return to their ground state, following clearly defined paths according to quantum probabilities, they emit photons of very specific energy. As the energy levels of the two states are fixed, all the photons have the same energy and this determines the wavelength of the light. This energy corresponds to particular wavelengths of light, and so produces particular colors of light. Each element produce a unique emission spectrum, because of that scientist are able to identify elements as per the color of their flame.

Sodium burns with a yellow flame, calcium with an orange, barium with a green.

Lithium burns with a red flame.

Author: de

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One Response

  1. Kevin Bjornson

    November 13, 2021 5:26 am

    If the heat applied to lithium (or a lithium compound) were less than the temp of a flame, would the lithium still emit light? Would the nm of the light be dependent on the temp of the heat? Could the lithium be encased with ceramic and electricity applied to both ends, to produce the heat (similar to heated gas in an arc tube but remaining solid)?


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