In chapter seven, we learned about the electronic structure of an atom. We learned about the Bohr model, electromagnetic energy and many other related topics. In this essay I will explain in more detail what light actually is and how we describe it. I will describe the behavior of electrons both in a hydrogen atom and in all atoms. I will explain the arrangement of elements in the periodic table, indicate which electrons are chemically important in atoms, and finally describe the properties of atoms and their relationship to their electronic arrangements. The information provided will be my interpretation of the chapter and my view of the topic of that chapter. Light is the natural agent that stimulates sight and makes things visible. White light is a mixture of colors that can be separated by a prism. Sources of white light would include the sun and light bulbs. In chemistry, we think of light as electromagnetic radiation. This electromagnetic energy travels through space in the form of waves, at the speed of light. In other words, we believe that light is a form of energy and that's primarily what light is, it's just energy. Now, the description of light is a more difficult concept to understand. We describe light using wavelength and frequency. The wavelength would be the distance between two corresponding points on a wave. The frequency would be the number of waves that pass through a point per second. For example, wavelengths of visible light, such as red, would be visible at seven hundred nanometers. Another example of how we describe light is to take the color green, for it to be visible it would have a wavelength of five hundred nanometers and a frequency of 6 x 10 14/s. Light can also be described on our scale as waves and particles or packets of light called photons. The energy of a photon is proportional to frequency. The final way to describe light is using the atomic spectrum. Atomic spectra only give specific colors in a line spectrum, where each line corresponds to a specific wavelength of light. For example, colored light, such as from a neon sign, would work perfectly with the atomic spectrum. The Bohr model of the hydrogen atom is the primary tool for describing the behavior of the electron in a hydrogen atom. Niels Bohr studied the line spectra of the hydrogen atom to try to understand how electrons fit into models of hydrogen atoms..