9781422279458

79

Gold

protons in the nucleus of the atom. Each element has a unique atomic number. Gold has an atomic number of 79 because it has 79 protons in its nucleus. The nucleus of an atom may also contain neutrons. When an atom has the same number of protons as an element on the chart, but a different number of neutrons, it is called an isotope . Each element on the periodic table has its own unique chemical and physical properties. The chart helps keep track of elements with certain chemical properties by arranging them into columns, groups, or rows. In addition to the atomic number, each square in the periodic table also lists the name of the element and its chemical symbol (Au for gold), along with other important information such as the number of neutrons in the nucleus of one atom of an element, the number of electrons that surround the nucleus, the atomic mass, and the general size of the atom. The periodic table is a very useful tool as one begins to investigate chemistry and science in general. (For lots more on the periodic table, read Understanding the Periodic Table , another book in this series.) This book is about the element gold. Its name comes from the Anglo-Saxon word for gold, aurum . Humans have recognized the beauty and uniqueness of this shiny yellow metal since ancient times.

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