Periodic Nature of Elements

To say... that a man is made up of certain chemical elements is a satisfactory description only for those 

The elements that directly precede the inert gases—fluorine, chlorine, bromine, iodine, and astatine, with 9, 17, 35, 53, and 85 electrons, respectively—also resemble each other. They are nonmetals, poor heat and electric conductors, and form salts when reacted with the alkali metals. Therefore, these elements are called halogens, or salt-formers, that form acidic solutions in water. 

The elements that fall between the alkali metals and the halogens show a progressive gradation of properties between the two extranes. For instance, the elements such as magnesium (12 electrons), aluminum (13), silicon (14), phosphorus (15), and sulfur (16), which faU between sodium (11) and chlorine (17), show a decrease in metallic character and an increasing tendency to form less alkaline and more acidic solutions in water. 

Those elements that lie midway between the alkali metals and the halogens are special to the Ufe sciences. These elements—carbon (6), silicon (14), germanium (32), tin (50), and lead (82), include 

Families (or groups) of elements are arranged vertically in the periodic chart. These are the elements with similar chemical and physical properties, although these properties weaken from top to bottom. Elements at the top of the chart are lighter and less dense elements at the bottom have greater masses and are more dense. Elements arranged horizontally form a recurring pattern 

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