Ozone layer bromine (Br). While there are natural sources for all of these species, the concentrations of chlorine and bromine increased markedly in recent decades because of the release of large quantities of man-made organohalogen compounds, especially chlorofluorocarbons (CFCs) and bromofluorocarbons. These highly stable compounds are capable of surviving the rise to the stratosphere, where Cl and Br radicals are liberated by the action of ultraviolet light. Each radical is then free to initiate and catalyze a chain reaction capable of breaking down over 100,000 ozone molecules. By 2009, nitrous oxide was the largest ozone-depleting substance (ODS) emitted through human activities. The
Layer by Layer starts by making a cross on one face with the edge pieces, then putting the corners into position between the edges. By then the layer should be solved. Third, the four edge pieces of the middle layer are solved. At this point the first two layers are solved. Fourth, a cross of the opposite color is made on the last layer. Fifth, the last layer edges are permutated (swapped around). Sixth, the last layer corners are permutated. Finally, the last layer corners are oriented. Most Layer by Layer beginners' methods solve the first two layers using the same technique. However,