[Chemistry Class Notes] on Silicon Pdf for Exam

Silicon was not characterized in its pure form until the year 1824 when Jons Jakob Berzelius first managed to do so. And it was because of the fact that silicon has a high chemical affinity to oxygen. Silicates, which contain silicon and oxygen, are formed by the oxides form of the silicon. The melting point is surpassed by only boron out of all the metalloids and nonmetals.

Silicon is a member of the carbon family and is a non-metallic chemical element, having atomic number 14, and belongs to group 14, period 3 in the p-block of the periodic table. Carbon is above it, while the elements like germanium, tin, lead, and flerovium are below it. Silicon is  metallic, one of the seven elements which have both the characteristics of non-metal and metal depending upon the other element to which it combines. Silicon used in electronics acts as metals, while the glass which is a silicon compound has non-metallic qualities. This element is denoted as ‘Si’. Electronic configuration of silicon is (Ne) 3s2 3p2. The state of silicon is solid at 20°C. It is used in moulding compounds.

Silicon is a hard yet breakable crystalline solid, and it has a bluish-grey metallic lustre, and also Silicon is tetravalent, that is to say, its valency is 4, it is also a semiconductor. Silicon is, for the most part, unreactive.

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Occurrence in Nature

Silicon is the second most abundant electropositive element which makes up 27.7% of the Earth’s crust by mass. It occurs in combined form in nature as silicon dioxide which is commonly known as silica. About 97% of Earth’s crust is made of rocks and comprises silicon and oxygen compounds. Silicon exists in nature in many dioxide forms, making compounds with oxygen, phosphorus, magnesium, and others. The minerals which contain silicon dioxide are known as silicates. 

Properties of Silicon

Being a metalloid, silicon also occurs in two allotropic forms. Allotropes are the element forms which have various chemical and physical properties.

 

Physical Properties of Silicon

1. One silicon’s allotrope is in the form of needle-like, shiny, greyish-black crystals or flat plates, while the other one has no crystal structure and it exists usually as a brown powder.

2. The atomic number of silicon is 14 and its relative atomic mass is 28.085 u.

3. The density of silicon is 2.3296 grams per cubic centimetre.

4. The silicon melting point is 1,410°C and the silicon boiling point is 3,265°C.

5. Silicon in its purest form is an intrinsic semiconductor Although adding impurities in small amounts helps in highly increasing the intensity of semiconductor.

 

Chemical Properties of Silicon

1. Silicon is purely electropositive in its chemical behaviour, has a metallic lustre, and is considered to be very brittle.

2. Silicon is very similar to metals in terms of chemical behaviour.

3. At room temperature, silicon is a relatively inactive element. Being solid, it does not combine with oxygen or other most related elements.

4. Silicon is very reactive at higher temperatures.

5. Silicon combines with oxygen, phosphorus, nitrogen, and other elements. It also forms alloys in the molten state.

Compounds/Polymers of Silicon (Silicon Materials)

• Silanes:- Silanes are very strong reducing agents and consist of homologous series of compounds such as silicon hydrides. When exposed to air, these polymers are very reactive and can easily catch fire. At room temperature, they are unstable.

• Silicides:- Silicides have similar structures to borides and carbides. Due to their similar structure, the heat of formation of these elements is similar. Silicon carbide is also known as Carborundum which is widely used as powdery material to polish or grind other material and has refractory properties.

• Silica:- Silica (Silicon dioxide)  mainly consists of granite and sandstone which is used in the manufacture of glass, abrasives, in water filtration, as a food additive, and many more.

• Halides:- Silicon compounds, mostly carbides, form silicon tetrahalides when they react with stable halogens. Unlike carbon tetrahalides, these readily hydrolyze in water.

• Silicic Acids:- Hydrated silica gels are formed as a result of increasing water concentration. Most silica gels are found to occur in an aqueous state.

 

Uses of Silicon

1. Silicon is used in the production of ceramics, bricks, and fire bricks.

2. Silicon is used to make many alloys such as aluminium–silicon and ferrosilicon known as iron–silicon which is widely used in the steel industry.

3. Silicon is used to make polymers of silicon-oxygen with the methyl group attached known as silicones and its oil is a lubricant added in hair conditioner and cosmetics.

4. Silicone rubber is used in waterproofing systems in bathrooms, roofs, and pipes.

5. Being a semiconductor, silicon is used in transistors and solid-state devices including microelectron
   ics and the computer industry.

6. The unprocessed form of silicon is used in the making of silica sand, clays, and stone. 

7. For Portland, which is the most common type of cement, silicates are used.

8. Silicon which is highly purified is also used in semiconductor electronics.

Fun Facts

1. In 1824, Silicon was discovered by Jons Jacob Berzelius.

2. The atomic structure of silicon has 14 electrons having 4 electrons in the outermost shell (having the highest energy level), 8 electrons in the second orbit, and 2 electrons in the first orbit.

 

Silicon Boiling Point

By heating silicon dioxide, silicon is prepared which is 96% to 98% pure. Various applications of silicon require it in a pure form which is known as hyper-pure silicon. It’s considered to be 99.7% pure.