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Semi-Metals_E_Block

Page history last edited by PBworks 13 years, 9 months ago


SEMI-METALS/METALLOIDS

 

Metalloids are the borderline between metals and non-metals. Elements that are metalloids have some properties of metals and some properties of non-metals. For example some metalloids can have a high melting point (like a metal) yet have a low density (like a non-metal). The metalloids are Boron, Silicon, Germanium, Polonium, Tellurium, Astatine, Arsenic, and Antimony. These elements all rest next to the staircase (imaginary line on the table from boron diagonally going down to astatine) whether above or below.

 

The Periodic Table of Elements--The location of the metalloids:

 

Below is some basic information on the metalloids. We have their symbol, atomic number, atmoic mass, a few properties, and a few uses for metalloids.


 

Physical Properties of Metalloids

 

What makes elements metalloids is some of them share properties of metals, while at the same time they share properties of non-metals.

 

Here is a table of the properties of metals and non-metals.


Properties of metals:

1)Shiny

2)high density

3)high melting point

4)ductile

5)sonorous

6)malleable

 

Properties of non-metals:

1)Dull

2)low density

3)low melting point

4)not ductile

5)not sonorous

6)brittle


 

As mentioned before, the metalloids share some physical properties of metals and non-metals.

 

1)For example, boron, like many other metalsis ductile. On the other hand, boron isn't very dense, sharing a common physical porperty with many non-metals.

 

2)Another example is silicon. It is very shiny, like many metals, but like a non-metal, it is brittle, not malleable.

 

3)Also, germanium share the same two physical properties mentioned in silicon above.


 

Chemical Properties of Metalloids

 

Since metalloids are part metal and part non-metal, many of the chemical properties they share are between the chemical propterties of metals and non-metals.

 

Metalloids are semiconuctors: The metalloids' ablility to conduct is between those of a metal and those of a non-metal. They conduct electricity better than non-metals (which don't conduct electricity at all), but they don't conduct as well as other metals.

 

Ionization: Ionization occurs when an atom loses an electron and is no longer neutral. Ionization energies for metalloids are between those of metals and those of non-metals.

 

Reactivity: The reactivity of a metalloid depends on the element they are reacting with. For example, boron acts as a nonmetal when reacting with sodium yet as a metal when reacting with fluorine.

 

Also...

Electronegativities between those of metals and nonmetals

Metalloids can conduct heat


 

 

Boron

__Symbol: __B

Atomic Number: 5

Atomic Weight: 11

Discovered by: Sir Humphry Davy and J.L Gay-Lussac

Discovered in: 1808

__Word Origin: __joining the two words borax and carbon together

Properties: Boron is a brown substance. The melting point of boron is 2003 °C and the boiling point of boron is 2550 °C . At a lower temperature boron is a poor conductor, but at a higher temperature boron is a good conductor. The density of boron is 2.3g/cm^3.

Metallic Properties: High melting point, can conduct electricity, conducts heat well, ductile, and shiny

Non Metallic Properties: Fairly low density

Uses: Boron filaments are used for advanced aerospace structures because they are strong yet light (that is what makes them a metalloid). A compound of of boron is borax (sodium tetraborate decahydrate Na2B4O7 • 10H2O); borax (formed by boron)is most commonly used as cosmetics or laundry products (ie. a household bleaching agent).

Sources: You can obtain boron from kernite. Boron is created when humans manufacture glass, combusting coal, etc. Plants, over a period of time, absorb boron.

 

Here is the atomic structure of boron:

The first shell holds two electrons and the second shell holds three.

 

A picture of boron:


 

Silicon

__Symbol: __Si

Atomic Number: 14

Atomic Weight: 28.0855

Discovered: Berzelius, 1824

Word Origin: Latin: silicis, silex: flint

Properties: The melting point of silicon is 1410°C and the boiling point is 2355°C. Silicon is fairly motionless, but is attacked by watered-down alkali and by halogens. The element transmits over 95% of all infrared wavelengths. It has a valence of 4.

Uses: Silicon is one of the most widely used elements. It is most important for plant and animal life. Silicon is used to produce transistors, solar cells, rectifiers, and other important electronic devices.

__Sources: __Silicon is the second most abundant resource of the world, and the first most abundant resource we have is oxygen. Silicon itself makes up 25.7% of the earth’s crust. Silicon is found in many places, such as the sun, starts, and meteorites. On earth, it is not found openly in nature, and is commonly included in sand, quartz, amethyst, agate, flint, jasper, opal, and citrine.

 

Here is the atomic structure for silicon:

 

A picture of silicon:


 

Germanium

__Symbol: __Ge

__Atomic Number: __32

Atomic Weight: 72.59

__Discovered: __1886

__Word Origin: __Latin Germania: Germany

__Properties: __Germanium has a melting point of 937.4°C, and a boiling point of 2830°C. It is crystalline and brittle, and keeps its gleam in air. The element and its oxide are transparent to infrared light. Germanium has the valences of 2 and 4.

__Uses: __The gas germanium produces, germanium oxide, is used almost, if not more, as much as the metalloid itself. Germanium and its oxide are used in highly sensitive infrared detectors and other optical devices. The element has a high index of refraction and distribution of germanium oxide, and that has led to its use in glasses in microscopes and camera lenses. Germanium may be toxic and can’t be used bacteria, but it can be used on most mammals.

__Sources: __Germanium can be separated from other metals by using fractional distillation. The dioxide is reduced with hydrogen to give the element. Zone refining techniques allow for the production of ultra-pure germanium. Germanium is found in argyrodite, germanite, coal, zinc ores, and in other minerals.

 

Electron configuration for germanium:

 


 

Tellurium

__Symbol: __Te

__Atomic No.: __52

__Atomic Mass: __127.6

__Melting Point: __449.8°C

__Boiling Point: __1390°C

__Word Origin:__Named from the Latin word ‘tellus’ that means earth.

__Properties:__Tellurium is the rarest out of all the oxygen grouped elements.

It has many metallic properties.

Tellurium is used for giving colors for vases; helping mix metal, helps making stainless steel.

 

Electron configuration for tellurium:

 

A picture of tellurium


 

Astatine

__Symbol: __At

Atomic No.: 85

Atomic Mass: 210

__Word Origin:__Named from Greek word astatos that means instability.

__Properties:__Astatine is rarely found in nature and most of it is artificially made.

Naturally found astatine has half-life less than a minute.

Its chemical properties are simila to that of Iodine, but have more of metallic property.

Currently no use in technology.

 

Electron configuration for astatine>

 

A pictured of Astatine:


 

Arsenic

Symbol: As

Atomic Number: 33

Mass Number: 75

__Word Origin:__Named from the Greek word arsenikos and the Latin word arsenicum.

__Properties:__Arsenic has a melting point of 817.0 °C and a boiling point of 613.0 °C. Gray arsenic is steel-gray in color, crystalline, very brittle, semimetallic, and tarnishes readily in air. When it is heated, arsenic rapidly oxidizes to arsenous oxide, which has an odor kind of like garlic. Arsenic and its compounds are poisonous.

__Uses:__It is used for poisons, it can conduct electricity and sometimes it is used as semiconductors.

Sources: Arsenic can be found in a mineral called mispickel.

 

Electron configuration for arsenic:

 

A picture of Arsenic:


 

Antimony

__Symbol:__Sb

Atomic Number: 51

Mass Number: 122

Word Origin: Greek anti plus monos, meaning a metal not found alone.

Properties: Antimony has a melting point 630.74°C, and a boiling point of 1950°C. Metallic antimony is extremely brittle. It is a bluish white metal with a flaky crystalline texture and metallic luster. It is not oxidized by air at room temperature. However, it will burn brilliantly when heated, releasing white fumes. It is a poor heat or electrical conductor.

__Uses:__Antimony is widely used in alloying to increase hardness and mechanical strength.

Sources: Antimony is found in over 100 minerals.

 

Electron configuration for antimony:

 

A pictuer of antimony

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