Medium = substitution is possible but there may be an economic and/or performance impact High = substitution not possible or very difficult. The availability of suitable substitutes for a given commodity. A higher recycling rate may reduce risk to supply.

The percentage of a commodity which is recycled. The number of atoms of the element per 1 million atoms of the Earth’s crust. This is calculated by combining the scores for crustal abundance, reserve distribution, production concentration, substitutability, recycling rate and political stability scores. The Chemical Abstracts Service registry number is a unique identifier of a particular chemical, designed to prevent confusion arising from different languages and naming systems.ĭata for this section been provided by the British Geological Survey.Īn integrated supply risk index from 1 (very low risk) to 10 (very high risk). Where more than one isotope exists, the value given is the abundance weighted average.Ītoms of the same element with different numbers of neutrons. This is approximately the sum of the number of protons and neutrons in the nucleus. The mass of an atom relative to that of carbon-12.

The transition of a substance directly from the solid to the gas phase without passing through a liquid phase.ĭensity is the mass of a substance that would fill 1 cm 3 at room temperature. The temperature at which the liquid–gas phase change occurs. The temperature at which the solid–liquid phase change occurs. The arrangements of electrons above the last (closed shell) noble gas. These blocks are named for the characteristic spectra they produce: sharp (s), principal (p), diffuse (d), and fundamental (f). The atomic number of each element increases by one, reading from left to right.Įlements are organised into blocks by the orbital type in which the outer electrons are found. Members of a group typically have similar properties and electron configurations in their outer shell.Ī horizontal row in the periodic table.

Hydrates zeolites are used as ion exchangers in softening of “hard” water.A vertical column in the periodic table.

Zeolites are complex aluminium silicates.

e.g., ZSM-5 (A type of zeolite) used to convert alcohols directly into gasoline.

Zeolites are widely used as a catalyst in petrochemical industries for cracking of hydrocarbons and isomerisation,.

Aluminosilicate are formed when few Si atoms are replaced by Al atoms in three-dimensional network of silicon dioxide.

Two important man-made silicates are glass and cement.

The basic structural unit of silicates is SiO -4 4. Some of the examples are feldspar, zeolites, mica and asbestos.

A large number of silicates minerals exist in nature.

It is used as lubricants (Vaseline), insulators etc.

It is chemically inert, water repellent, heat resistant.

They are manufactured from alkyl substituted chlorosilanes. The linear, cyclic or cross-linked polymeric compounds containing (R 2SIO) as a repeating unit, are known as silicones.

An amorphous form of silica, kieselghur is used in filtration plants.

Silica gel is used as adsorbent in chromatography.

Quartz is extensively used as a piezoelectric material.

At elevated temperature it does not reacts with halogens, dihydrogen and most of the acids and metals.

In normal form silica is very less reactive.

Each oxygen atom in turn covalently bonded to another silicon atoms as shown below: Each silicon atom is covalently bonded in a tetrahedral manner to four oxygen atoms. Silicon dioxide is a covalent three-dimensional network solid. Silicon dioxide, commonly known as silica, occurs in various crystallographic forms.įor example, Quartz, Cristobalite and thermite are some of the crystalline forms of silica.

But increase in combustion of fossil fuels and decomposition of limestone for cement manufacture increase of C0 2 in the atomosphere is one of the main reasons of green-house effect.

When C0 2 dissolves in water only some of the molecules react with water to form carbonic acid. It is prepared by complete combustion of carbon and carbon containing fuels in excess of air. CO is used in the extraction of many metals from their oxide ores.Ĭarbon Dioxide CO 2 Preparation of Carbon Dioxide:

It is colourless, odourless and almost water insoluble gas.

Compounds of silicon