Periodic Table - Gap Filling Quiz 2

Gap-Filling Quiz

Type the answers (or copy and paste them) into the blank boxes.
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   Alkali      atomic      chemical      Earth      eight      Halogens      helium      labelled      lithium      Mendeleev      number      orbitals      Periodic      periods      seven      three      two   
The Periodic Table is an arrangement of elements in order of increasing number. It was first drawn up by the Russian chemist named Dimitri in 1869. It was later found that by placing the then known elements in order of increasing atomic , the properties of the elements repeat themselves at regular intervals. The elements were thus arranged so that those elements with similar properties were placed under one another in a vertical column called a group. The first group in the Periodic Table is Group I, and the elements of this group are called the metals. All of the elements in this group have a single electron in their outermost shell, and have similar properties. The second group is called Group II, or the Alkaline metals. Likewise, all the elements in this group have similar chemical properties, but have electrons in their outer shell. The Group VII elements are known as the . The atoms of these elements have electrons in their outer shell, and once again have similar properties. The horizontal rows are known as . There are seven periods in the Table. The first period contains two elements, hydrogen and . The second period contains eight elements, beginning with and ending with neon. The third and fourth periods have and eighteen elements respectively. The periods are usually n=1, n=2, etc. The period number tells us how many (or shells of electrons) that an atom has. For instance, silicon is in the third period, thus it will contain orbitals, or electron shells.