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separate, substances. There are 92 elements that can be found nat- urally on Earth and in space. The remaining 26 (and counting) have been manufactured and analyzed in a laboratory setting. These ele- ments, alone or in combination with others, form and shape all the matter around us. From the air we breathe, to the water we drink, to the food we eat—all these things are made of elements. We can learn a lot about an element just by finding its location on the periodic table. The periodic table is arranged into rows and columns by increasing atomic number. Each element has a unique atomic num- ber. It is the number of protons in the nucleus of the atom. For example, helium has an atomic number of 2—there are two protons in the nu- cleus of an atom of helium. (All samples of an element have the same number of protons, but they may have a different number of neutrons in the nucleus. Atoms with the same number of protons but different number of neutrons are called isotopes .) Each element on the periodic table is unique, having its own chemical and physical properties. Certain chemical properties can be interpreted based on which group or row an element is placed. The periodic table also gives important information such as the number of protons and neutrons in the nucleus of one atom of an element, the

The Chemistry of Everyday Elements

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