Who Invented The Periodic Table

Elements make up everything on the earth. Many different elements are discovered throughout the years. Elements that have already been discovered are arranged in a model called the periodic table. Dimitri Mendeleev founded the periodic table in 1869. The periodic table tells you many things about an element. It places elements in order relative atomic mass. Mendeleev realized that the characteristics of the elements where according to their atomic weight, so he arranged them so elements with the same properties would be in a column called a column. Column one is the alkali metals. Column two is the alkaline earth metals, Columns three thru twelve are called the transition metals. Column seventeen is the halogens. Lastly, column eighteen is the noble gases. These columns are used to divide

This group consist of Lithium, Sodium, Potassium, Rubidium, Cesium, and Francium. These metals are very soft and can usually be cut with a knife. They have a very low melting and boiling point. Densities of these elements are very small, and the electronegativity is low. Alkali metals are the most reactive metals. They react very strongly in the reaction with water. However, a couple of the alkali metals do not react well at all with any other element. For example, francium has the lowest electronegativity, which means that the power of an atom to attract electron density to itself is very unlikely. The alkali metals combine very readily with the halogen group. This is because the alkali metals have one valence electron that they are ready to lose, and the halogens have seven valences electrons. The stable outer shell of a compound is to have eight electrons. The one electron from the alkali metal would give the compound eight valence electrons which is a necessity according to the octet rule. Some compounds that are formed from this group are sodium chloride, potassium hydroxide, sodium hydroxide, and potassium