The Periodic Table shows all the elements known to exist. The first 98 are now said to be naturally occurring. The elements with atomic numbers higher than 98 have been made by scientists. In 2015 the discovery of elements 113, 115, 117 and 118 was announced by IUPAC (International Union of Pure and Applied Chemistry). These discoveries completed the seventh row of the Periodic Table, an important milestone in the chemical world. The elements were given the temporary symbols Uut, Uup, Uus and Uuo until their actual names and symbols are proposed and agreed. The Periodic Table classifies elements as metals and non-metals.
Fig. 5 The Periodic Table of the Elements. Elements with atomic numbers 58–71 and 90–103 are not shown. Activity
Arranging the elements
Use the 20 index cards with the Bohr models of the atoms that were made in Chapter 22, page 242 to answer the following questions: 1. Which elements have a full outermost energy level? 2. Which elements have just one electron in their outermost energy level? 3. Which elements are just one electron short of a full outermost energy level? 4. Where are the elements that have one electron in their outermost shell located on the Periodic Table?
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5. Where are all the elements that have a full outermost shell located on the Periodic Table? 6. What clues does this give you about how the Periodic Table is organised?
