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Course Outline

General Chemistry

04/25/09

 

 


Periodic Table: Metals, Non-metals, and Semi-metals


periodic table

 

There are three fundamental categories of elements: metals, non-metals, and semi-metals (also called metalloids).  You can deduce which type an element is by its location on the periodic table.

Metals are elements that are shiny, malleable (can be pounded into a sheet), ductile (can be drawn into a wire), and good conductors of heat and electricity. Silver and mercury are examples of metals. Metals are found on the left of periodic table.

Non-metals are elements that are brittle and insulators of heat and electricity. Except for hydrogen, the non-metals are at the upper right of the periodic table. Chlorine is another example of a non-metal.

Semi-metals, also called metalloids, are the elements boron, silicon, germanium, arsenic, antimony, tellurium, and astatine. These elements have properties somewhat like those of metals and somewhat like those of non-metals. They are located along the semi-metal line of the periodic table. To find the semi-metal line, locate boron, atomic symbol B, on a periodic table. Draw a stair step line down the left side of the boron square and across the bottom. Extend the line down the next horizontal row between aluminum, Al, and silicon, Si. Extend the line horizontally to the right below silicon, then down the next row. Continue in this pattern until you have drawn a zig-zag from boron to astatine. All the elements that share a straight side on this line except for aluminum and polonium are semi-metals.

Once you have located the semi-metals, you can categorize any element. If an element appears to the left of the semi-metas (and it isn't hydrogen), that element is a metal. In addition, aluminum and polonium on the semi-metal line are metals. Every element to the right of the semi-metals is a non-metal.

 

 periodic table with the location of the semi-metals

 


Concept Check: What type of element is indium, In? What type of element is Se?

Answer: Indium (symbol In) is a metal. Se (the symbol for selenium) is a non-metal.

 


 

 

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