Silicon and its Characteristics

Silicon is a chemical element with chemical symbol Si and atomic number.It is a hard, brittle crystalline solid with a blue-gray metallic luster and is a tetravalent metalloid and semiconductor.It is a member of group 14 on the periodic table: carbon is above it; germanium, tin, lead, and praseodymium are below it.It is relatively inactive.Due to its high chemical affinity for oxygen, it was not until 1823 that Jöns Jakob Berzelius was first able to prepare it and characterize it in pure form.Its oxides form a family of anions called silicates. Its melting point and boiling point are 1414°C and 3265°C respectively, ranking second among all metalloids and nonmetals, second only to boron.Silicon is the eighth most common element in the universe by mass, but rarely occurs as a pure element in the Earth's crust.It is widely distributed in space in cosmic dust, asteroids and planets in various forms of silica (silicon dioxide) or silicates. More than 90% of the Earth's crust is composed of silicate minerals, making silicon the second most abundant element in the Earth's crust (approximately 28% by mass), after oxygen.

Most silicon is used commercially without isolation, often with minimal processing of the natural mineral.Such uses include industrial construction using clay, silica sand and stone.Silicates are used in Portland cement for mortars and stuccoes, and mixed with silica sand and gravel to make concrete for sidewalks, foundations, and roads.They are also used in white ceramics such as porcelain, as well as traditional silicate-based soda lime glass and many other specialty glasses.Silicon compounds such as silicon carbide are used as abrasives and components of high-strength ceramics.Silicon is the basis of the widely used synthetic polymer silicone.

The end of the 20th century to the beginning of the 21st century is known as the Silicon Age (also known as the Digital Age or Information Age) due to the enormous impact of the element silicon on the modern world economy.The small fraction of very high-purity elemental silicon (<10%[citation needed]) used in semiconductor electronics is critical to the transistors and integrated circuit chips used in most modern technologies such as smartphones and other computers.In 2019, 32.4% of the semiconductor market was used in networking and communication equipment, and the semiconductor industry is expected to reach $726.73 billion by 2027.Silicon is an essential element in biology.Most animals only need traces, but some sea sponges and microbes, such as diatoms and radiolarians, secrete skeletal structures made of silica. Silica is deposited in many plant tissues.

Characteristics

Physical and atomic:

A silicon atom has fourteen electrons. In the ground state, they are arranged in the electronic configuration [Ne]3s23p2.Of these, four are valence electrons, occupying the 3s orbital and two 3p orbitals.Like other members of its group, the lighter carbon and the heavier germanium, tin and lead, it has the same number of valence electrons as the valence orbitals: thus, it can complete its octet and achieve stable inertness by The gas argon configuration forms sp3 hybrid orbitals, forming tetrahedral SiX.4 derivatives in which the central silicon atom shares an electron pair with each of the four atoms to which it is bonded.The first four ionization energies of silicon are 786.3, 1576.5, 3228.3 and 4354.4 kJ/mol; these numbers are high enough to rule out the possibility of simple cationic chemistry of the element.Following the periodic trend, its single-bond covalent radius is 117.6 pm, which is between that of carbon (77.2 pm) and germanium (122.3 pm).

Electrical

At standard temperature and pressure, silicon is a shiny semiconductor with a blue-gray metallic luster; as a typical semiconductor, its resistivity decreases with increasing temperature.This occurs because silicon has a small energy gap (bandgap) between its highest occupied energy level (valence band) and lowest unoccupied energy level (conduction band).The Fermi level is roughly halfway between the valence and conduction bands and is the energy at which a state is likely to be occupied by electrons.Therefore, pure silicon is effectively an insulator at room temperature.However, doping silicon with photoactive elements such as phosphorus, arsenic, or antimony introduces an extra electron per dopant, which may then be excited thermally or photolytically into the conduction band, forming n-type semiconductor. Likewise, doping silicon with group 13 elements such as boron, aluminum, or gallium leads to the introduction of acceptor levels that trap electrons that might be excited from the filled valence band, forming a p-type semiconductor.Connecting n-type silicon to p-type silicon creates a p-n junction with a common Fermi level; electrons flow from n to p, while holes flow from p to n, creating a voltage drop. So this p-n junction acts like a diode and rectifies the alternating current, making it easier for the current to flow one way rather than the other.The transistor is an n-p-n junction with a thin layer of weak p-type silicon between two n-type regions.Biasing the emitter by a small forward voltage and the collector by a large reverse voltage allows the transistor to act as a triode amplifier.

Crystal structure

Under standard conditions, silicon crystallizes in giant covalent structures, especially in the diamond cubic lattice (space group 227). Therefore, it has a high melting point of 1414 °C because a lot of energy is required to break the strong covalent bonds and melt the solid.After melting silicon, the network of long-range tetrahedral bonds is broken and the voids in the network are filled, similar to water ice when hydrogen bonds are broken during melting.It does not have any thermodynamically stable allotrope at standard pressure, but several other crystal structures are known at higher pressures.The general trend is that the coordination number increases with pressure, eventually forming a hexagonal close-packed allotrope of about 40 GPa, called Si-VII (the standard variant is Si-I).The allotrope known as BC8 (or bc8) has a body-centered cubic lattice with eight atoms per original unit cell (space group 206), can be produced at high pressure and remain metastable at low pressure.Its properties have been studied in detail.

Silicon boils at 3265 °C: although high, it is still lower than the temperature at which its lighter congener carbon sublimes (3642 °C), and the heat of vaporization of silicon is also lower than that of carbon, which is related to the ratio of Si– Si bonds to C.The C bond is weak.Graphene-like layers of silicene can also be built.

Isotopes

Naturally occurring silicon consists of three stable isotopes, 28Si (92.23%), 29Si (4.67%) and 30Si (3.10%).Of these, only 29Si can be used for NMR and EPR spectroscopy,because it is the only substance with a nuclear spin (I = 1/2).All three are produced by the oxygen combustion process in Type Ia supernovae [49][50], where 28Si is produced as part of the alpha process and is therefore the most abundant.28Si fuses with alpha particles in stars via photodecay rearrangement, a process known as silicon burning; this is the final stage of nucleosynthesis before the star rapidly collapses and explodes violently in a Type II supernova.

Twenty radioisotopes have been characterized, the two most stable being 32Si with a half-life of about 150 years and 31Si with a half-life of 2.62 hours.All remaining radioisotopes have half-lives of less than seven seconds, and most have half-lives of less than one-tenth of a second.Silicon has one known nuclear isomer, 34mSi, with a half-life of less than 210 ns.32Si undergoes low energy beta decay to 32P and then stabilizes to 32S. 31Si can be produced by neutron activation of natural silicon and thus can be used for quantitative analysis; it can be easily detected by its stable 31P characteristic beta decay, where the emitted electrons carry energies up to 1.48 MeV.

Known isotopes of silicon have masses ranging from 22 to 44.The most common decay mode for isotopes with masses lower than the three stable isotopes is reverse beta decay, with the predominant formation of the aluminum isotope (13 protons) as the decay product.The most common mode of decay for heavier unstable isotopes is beta decay, with the predominant formation of the phosphorus isotope (15 protons) as the decay product.Silicon can enter the ocean through groundwater and river transport.The bulk groundwater input has a different isotopic composition than the fluvial silicon input.Isotope changes in groundwater and river transport lead to changes in 30Si values in the oceans.At present, there are large differences in deep-water isotope values in various ocean basins in the world.Between the Atlantic Ocean and the Pacific Ocean, there is a deep-water 30Si gradient greater than 0.3‰.30Si is most often associated with productivity.