Our goal for this next unit is to find out exactly where those electrons are within an atom. We know that energy comes in a variety of forms, one of which is light, and that light can behave as a wave or as a particle known as a photon. We have also seen two ways that matter responds to an input of energy. One is the observation of blackbody radiation. When energy is applied in the form of heat, the sample responds by emitting light in the visible spectrum. Similarly, for the photoelectric effect, we see electrons released when electromagnetic radiation of a minimum frequency is applied. There is actually an entire field known as spectroscopy that studies how light interacts with matter. In this lesson, we will look closely at how individual atoms respond to energy and learn what that response can tell me about an atom's structure. This is known as atomic spectroscopy (the study of how electromagnetic radiation is absorbed or emitted by atoms).
Have you wondered what makes the colors of fireworks? Well, the colors are due to the emission of light as electrons relax within an atom or ion. Yes, the electronic transitions within an atom produce the colors of fireworks! The colors emitted are unique for each element.
Here is a link to a video that demonstrates how different elements produce different colors of light when ignited. The balloons are filled with hydrogen gas and sprayed with salts. The balloon on the right is sprayed with a salt of lithium and the one one the left with a salt of copper. Examine how they give off different colors.
You may also have heard of neon signs; the kind that are on display in bars and restaurants. A true neon sign is red because the emission spectra of neon exhibits several wavelengths in the red-orange region of the electromagnetic spectrum. In the image below, you can see a neon bulb on the left, and its emission spectrum on the right.