Elements

Elements

1. Elements

   • There are 115 elements, 90 naturally occurring elements, and 25 synthetic elements. Based on their properties, all the elements can be divided into three classes: Metals, Non-Metals, and Metaloids.
     • Metals
       • Most of the elements are Metals. Most are silver or grey in color and shiny. They are good conductors of electricity and heat. They are also Malleable and Ductile. Malleable means that they can be beaten or rolled into sheets without crumbling. Ductile means they can be stretched into long wires.
         • Metals have many other properties in common, although there are differences. For example, most metals are solids at room temperature (25˚C). Mercury is the exception. It melts at -39˚C. Another variable characteristic is how strongly metals react with other substances. Some metals, such as sodium, are highly reactive with air and water. Others such as platinum and gold are Inert, or unreactive, except with the most corrosive acids.
     • Non-Metals
       • Only 17 elements are Non-Metals. They are grouped together mainly because of their lack of resemblance to metals, rather than their similarities to each other. For example, 11 of the non-metals are gases at 25˚ C, 5 are solids, and 1, bromine, is a red-brown liquid. There is also tremendous variation in color. Fluorine is pale green, and chlorine is yellow. Iodine is violet. Some non-metals exist in different forms. For example, phosphorus has a red form and a white form. Both forms are stable at room temperature. Carbon can exist in three forms.
         • Some non-metals are highly reactive . Fluorine, for example, can etch glass. Noble gases, such as helium, are generally unreactive. About half of the non-metals exist at 25˚C as connected groups of atoms of atoms called Molecules, such as oxygen. Others, such as neon , exist only as individual atoms.
     • Metalloids
       • The remaining elements are called Metalloids. and they have properties that are intermediate between metals and non-metals. For example, some metalloids conduct electricity, but not very well. Silicon, used in the manufacture of computer chips, is a metalloid. Boron and arsenic are also metalloids.