Why does sodium street lamp give off a yellow color; whereas neon light gives off a red color? Describe the energy levels of electrons in an atom; Why do some elements produce colorful flames? How can you identify an unknown element using flame test?
The Correct Answer and Explanation is:
Why does a sodium street lamp give off a yellow color, whereas a neon light gives off a red color?
The color emitted by elements like sodium and neon comes from their electrons transitioning between energy levels in the atoms. When sodium atoms are heated or excited by electricity, their electrons absorb energy and jump to higher energy levels. When these electrons fall back to their original (lower) energy levels, they release that energy in the form of visible light. In the case of sodium, the energy released corresponds to yellow light, particularly at a wavelength of around 589 nanometers. For neon, the electrons release energy at different levels, resulting in the emission of red-orange light, a combination of wavelengths with red being most prominent.
Energy Levels of Electrons in an Atom:
In an atom, electrons occupy specific energy levels or shells around the nucleus. These levels are quantized, meaning electrons can only exist at specific energy states—not in between. The closer an electron is to the nucleus, the lower its energy. When atoms absorb energy (from heat or electricity), electrons get “excited” and jump to higher energy levels. They are unstable there, so they soon fall back to lower levels, releasing energy as light. The color (or wavelength) of light depends on the difference in energy between the levels.
Why Do Some Elements Produce Colorful Flames?
Different elements have unique arrangements of energy levels, so the amount of energy released by their electrons during transitions is different. This causes each element to emit light at specific wavelengths, resulting in distinct flame colors—for example, lithium produces red, copper gives green/blue, and potassium shows violet. This is the basis of flame tests.
How to Identify an Unknown Element Using a Flame Test:
To identify an unknown element, a sample is placed in a flame, and the color of the flame is observed. Each element has a characteristic flame color, which can be compared to known standards. For more precision, a spectroscope can be used to examine the specific wavelengths of light emitted, confirming the identity of the element.
