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The periodic table is a chart that lists elements by atomic number and by electron arrangements

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Introduction

The periodic table The periodic table is a chart that lists elements by atomic number and by electron arrangements, so that elements with similar chemical properties are in the same column. It was first discovered in 1869 by Dmitry I. Mendeleev as a way of presenting all the elements so as to show their similarities and differences. The elements are arranged in increasing order of atomic number as you go from left to right across the table. The horizontal rows are called periods and the vertical rows are called groups. A noble gas is found at the right hand side of each period. There is a progression from metals to non-metals across each period. Elements found in groups for example alkali and halogens have a similar electronic configuration. The number of electrons in outer shell is the same as the number of the group (e.g. lithium 2�1). ...read more.

Middle

As with all metals, the alkali metals are malleable and are good conductors of heat and electricity. The alkali metals are softer than most other metals. Caesium and francium are the most reactive elements in this group. Alkali metals can explode if they are exposed to water. The alkaline earth elements are metallic elements found in the second group of the periodic table. All alkaline earth elements have an oxidation number of +2, making them very reactive. Because of their reactivity, the alkaline metals are not found free in nature. The 38 elements in groups 3 of the periodic table are called transition metals. As with all metals, the transition elements are malleable, and conduct electricity and heat. Another thing about transition metals is that their electrons they use to combine with other elements are present in more than one shell. This is the reason why they often show several common oxidation states. ...read more.

Conclusion

The term "halogen" means "salt-former" and compounds containing halogens are called "salts". All halogens have 7 electrons in their outer shells, giving them an oxidation number of -1. The halogens exist, at room temperature, in all three states of matter: The six noble gases are found in group 18 of the periodic table. These elements were considered to be inert gases until the 1960's, because their oxidation number of 0 prevents the noble gases from forming compounds readily. All noble gases have the maximum number of electrons possible in their outer shell (2 for Helium, 8 for all others), making them stable. The thirty rare earth elements are composed of the lanthanide and actinide series. One element of the lanthanide series and most of the elements in the actinide series are called trans-uranium, which means synthetic or man-made. All of the rare earth metals are found in group a of the periodic table, and the 6th and 7th periods. The Rare Earth Elements are made up of two series of elements, the Lanthanide and Actinide Series. ...read more.

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