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

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).
The blocks of elements between groups II and III are called transition metals. These are similar in many ways; they produce coloured compounds, have variable valency and are often used as catalysts. Elements 58 to 71 are known as rare earth elements. These elements are found on earth in only very small amounts.
Elements 90 to 103 are known as the actinide elements. They include most of the will known elements, which are found in nuclear reactions. The elements with larger atomic numbers than 92 do not occur naturally. They have all been produced artificially.

The different types if groups are: noble gases, alkali metals, alkali earth metals, transition metals, Rare earth metals, other metals, other non-metals and halogens.

The alkali metals are found in group 1 of the periodic table they are very reactive metals that do not occur freely in nature. These metals have only one electron in their outer shell. Therefore, they are ready to lose that one electron in ionic bonding with other elements. 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. ...

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The different types if groups are: noble gases, alkali metals, alkali earth metals, transition metals, Rare earth metals, other metals, other non-metals and halogens.

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. Iron, cobalt, and nickel, and they are the only elements known to produce a magnetic field.

The 7 elements classified as other metals are located in groups 13, 14, and 15. While these elements are malleable, they are not the same as the transition elements. These elements, unlike the transition elements, do not show variable oxidation states, and their valence electrons are only present in their outer shell. All of these elements are solid, have a relatively high density, and are opaque. They have oxidation numbers of +3, ±4, and -3.

Non-metals are the elements in groups 14-16 of the periodic table. Non-metals are not able to conduct electricity or heat very well. As opposed to metals, non-metallic elements are very brittle, and cannot be rolled into wires or pounded into sheets. The non-metals exist in two of the three states of matter at room temperature: gases (such as oxygen) and solids (such as carbon). The non-metals have no metallic shine, and do not reflect light. They have oxidation numbers of ±4, -3, and -2.

The halogens are five non-metallic elements found in group 17 of the periodic table. 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.