Check out the periodic table -- noble gases have eight electrons in their valence shell, making them fairly unreactive or inert; they're in the last group (column) of the table, group 18. Helium also has a closed-shell configuration with 2 valence electrons; it can count as a noble gas.
Alkali and alkali earth metals have one and two valence electrons respectively (discounting hydrogen, which has one valence e-, and helium, which has 2 e-). Nonmetals are your classic H, C, N, O, P, S and the halogens (F, Cl, Br, etc) -- the backbone of organic chemistry -- along with Se. Basically you can tell that any element with seven valence electrons (a halogen) or eight (because the noble gases count!) is a nonmetal.
But you need to have more information than the valence electron count to know whether an element is a metalloid or metal, because metalloids and poor metals occur in the same groups of the periodic table, meaning they have the same valence electron count.
2007-01-26 20:50:10
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answer #1
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answered by jazzy girl 3
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In chemistry, a metal (Greek: Metallon) is an element that readily forms positive ions (cations) and has metallic bonds. Metals are sometimes described as a lattice of positive ions surrounded by a cloud of delocalized electrons. The metals are one of the three groups of elements as distinguished by their ionization and bonding properties, along with the metalloids and nonmetals. On the periodic table, a diagonal line drawn from boron (B) to polonium (Po) separates the metals from the nonmetals. Most elements on this line are metalloids, sometimes called semi-metals; elements to the lower left are metals; elements to the upper right are nonmetals.
A modern definition of metals is that they have overlapping conduction bands and valence bands in their electronic structure. This definition opens up the category for metallic polymers and other organic metals, which have been made by researchers and employed in high-tech devices. These synthetic materials often have the characteristic silvery-grey reflectiveness of elemental metals.
The traditional definition focuses on the bulk properties of metals. They tend to be lustrous, ductile, malleable, and good conductors of electricity, while nonmetals are generally brittle (for solid nonmetals), lack lustre, and are insulators.
2007-01-26 22:18:55
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answer #2
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answered by ifureadthisur2close 2
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By looking at their position in periodic table. Noble gases are with closed electron shells. Metals are on the left side in first and second columns, (for example Sodium, Potassium, Calcium, Magnesium etc.). The elements in the fourth group, like carbon, silicon etc. are mostly internediate (they form oxides etc, as also carbides). 6th and 7th group elements like Oxygen, Chlroine etc. are decidely non-metallic.
Hydrogen behaves anomalously. Look at the periodic table and read a few lessons or articles.
The number of electrons in the valence shell decides their position in the periodic table. So, 1 free electron keeps it in the first column or group, 2 keeps it in the second group etc.
2007-01-26 20:49:39
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answer #3
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answered by Swamy 7
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1,2 or 3 makes it a metal. 4,5,6 or 7 a non-metal, and 8 (except helium) a noble gas.
It is very difficult to detect the metalloids just on the basis of the number of outer electrons, because they occur diagonally on the Periodic Table, and so the number of outer electrons changes. It could be 4 for silicon, or 5 for arsenic and so on.
2007-01-26 20:40:04
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answer #4
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answered by Gervald F 7
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metals usually have a positive charge while nonmetals are usually negative. Noble gases are inert meaning their valence electron is usually eight. To put it simply, noble gases' electron shells are always complete that's why they are nonreactive. they neither give nor share electrons.
2007-01-26 22:37:38
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answer #5
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answered by Anonymous
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The periodic table is divided in eighteen groups.
1st - alkali metals
2nd - alkaline-earth metals
3-12 - transition metals
17 - halogens
18 - noble gas
2007-01-26 22:41:18
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answer #6
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answered by . 6
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hit it with a hammer if it makes a noise its metal if you hit bench its gas
2007-01-26 20:37:54
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answer #7
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answered by q6656303 6
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