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Chemists use a test called an electrolysis test to determine if an element is metallic or non-metallic. This test consists of dissolving the element in acid and running an electric current through the solution. If the element is metallic, the atoms of the element will show a positive charge. That is they will seek the negative pole.

Formally it is stated as "those elements which, when in solution in a pure state, carry a positive charge and seek the negative pole, in an electric cell".

Properties of metals that are familiar to everyone include:

1. They are good conductors of heat and electricity
2. They are usually opaque to light
3. They have metallic luster

For example, chlorine, a typical non-metal, will readily enter into combination with another atom by adding one electron to an outer shell of seven: gaining an electron from or sharing a pair with the other atom. Whereas, an atom of say sodium, a typical metal, enters into combination by the loss of its single valence electron.

Metallic characteristics of the elements decrease and non-metallic characteristics increase with the increase of valence electrons. Also metallic characteristics increase with the number of electron shells. Therefore there is no sharp dividing line between the metals and the non-metals.

There are elements that are definitely on the border between metal and non-metal. These elements will show hybrid behavior. They are sometimes called metalloids. Many of them have been called semiconductors. This group of elements include boron, silicon, germanium, arsenic, antimony, tellurium, and astatine.

Their physical properties generally include:

1. They are good conductors of heat and electricity.
2. They are malleable and ductile in their solid state.
3. They show metallic luster.
4. They are opaque.
5. They have high density.
6. They are solids (except mercury)
7. They have crystal structure in which each atom is surrounded by eight to twelve near neighbors

1. They have one to four valence electrons.
2. They have low ionization potentials; they readily lose electrons.
3. They are good reducing agents.
4. They have hydroxides which are bases or amphoteric.
5. They are electropositive.