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What metal burns purple?

Published in Flame Tests 2 mins read

The metal that produces a characteristic purple flame when burned is Potassium.

Understanding Flame Coloration

When certain metal ions are heated in a flame, their electrons absorb energy and jump to higher energy levels. As these electrons fall back to their original energy levels, they emit light at specific wavelengths, which we perceive as distinct colors. This phenomenon is widely used in chemistry through a technique called a flame test to identify the presence of specific metal ions.

Potassium's Distinct Purple Hue

Potassium and its salts are well-known for producing a beautiful purple or violet color during a flame test. This coloration is a unique identifier for the element. However, observing this color can sometimes be challenging depending on the conditions:

  • Paler Hue: The purple color produced by potassium may appear paler than expected, often resembling a light lilac rather than a deep, vibrant purple.
  • Background Flame Interference: If you are using a burner with a naturally blue flame, it can be difficult to clearly see the subtle purple or violet tint produced by potassium, as the blue background can mask the color change. Using a cobalt glass filter can sometimes help by absorbing the yellow light from sodium impurities, which often contaminate samples and overpower the potassium flame.

Common Flame Test Colors

While potassium burns purple, many other metals produce different, equally vibrant colors, making flame tests a valuable analytical tool. Here's a quick overview of some common elements and their flame test colors:

Element Flame Color
Potassium Purple/Lilac
Lithium Red
Sodium Bright Orange/Yellow
Calcium Orange-Red
Strontium Bright Red
Barium Pale Green
Copper Blue-Green

Practical Application

Flame tests are not just laboratory curiosities; they have practical applications:

  • Chemical Analysis: Used in analytical chemistry to identify unknown metal ions in a sample.
  • Pyrotechnics: The vibrant colors seen in fireworks are achieved by incorporating different metal salts, including potassium salts for purplish effects.
  • Educational Demonstrations: A popular and visually engaging way to teach students about atomic structure and light emission.

For more information on the principles behind flame tests and atomic emission, you can explore resources like the Royal Society of Chemistry or Khan Academy.