90
An element, as defined in Chapter 1 "Chemistry, Matter, and Measurement", is a substance that cannot be broken down into simpler chemical substances. There are about 90 naturally occurring elements known on Earth. Using technology, scientists have been able to create nearly 30 additional elements that do not occur in nature. Today, chemistry recognizes 118 elementssome of which were created an atom at a time. Figure 2.1 "Samples of Elements" shows some of the chemical elements.