Group 14 (IVA)

Elements

The Carbon Group

• a periodic table group consisting of:– carbon (C), silicon (Si), germanium (Ge), tin (Sn), lead (Pb),

and ununquadium (Uuq)

• In modern IUPAC notation, it is called Group 14• In the old IUPAC and CAS systems, it was called Group IVB

and Group IVA, respectively • In the field of semiconductor physics, it is still universally

called Group IV• The group was once also known as the tetrels

– from Greek tetra, (four), stemming from the Roman numeral IV in the group names

– or from the fact that these elements have four valence electrons.

The Carbon Group• Appearance

– less apparent in group– Carbon has a dull black color (graphite); hard and transparent

(diamond)– Silicon and germanium are dull grey or black– Tin and lead have a shiny grey color

• General Reactivity– Carbon in the forms of graphite and diamond does not react

easily– Carbon oxidizes at high temperature (used as fuels)– Silicon, germanium, tin and lead are unreactive metals

• Occurrence and Extraction– carbon, tin and lead can all be found in the elemental form in

the Earth’s crust and are readily mined– silicon is found in mineral deposits and then purified

The Carbon Group• Physical Properties

– increasing metallic character (top to bottom), – structure from giant molecular lattices to giant metallic lattices– change in bonding from covalent to metallic causes a decrease

in:• melting point, boiling point, heat of atomization and

ionization energy– at the same time increasing metallic character causes a

general increase in density and conductivity– Diamond has a very high refractive index (reason for sparkle

and value as a jewel); at the same time the hardest natural substance known (important industrially)

– Silicon has a semi-conductor property (revolutionized the computer and microprocessor industries)

– Tin and lead are good conductors of electricity

The Carbon Group

• Chemical Properties– Chemical reactivity increases (from top to bottom)– carbon, is strikingly different from the others as it has the

unique ability to form stable compounds containing long chains and rings of carbon atoms

– Silicon is unreactive chemically because an oxide layer seals the surface from attack, and high temperatures are required for oxidation to occur

– Silicon does, however, react with fluorine at room temperature. It is not attacked by aqueous acids, but does react with concentrated alkalis

– Tin and lead are quite easily oxidised, tin usually to tin(IV) and lead to lead(II). Both tin and lead reduce the halogens.

The Carbon Group• Oxides

– There are many oxides formed for this group, common ones include CO (gas), CO2 (gas), SiO2 (solid), SnO2 (solid), PbO (solid)

• Carbon dioxide is essential to life as it is the source of carbon for plants

• During photosynthesis carbon is combined with water to form carbohydrates

• CO2 is acidic, as is CO under extreme conditions.

• SnO, SnO2, PbO and PbO2 are all amphoteric.

– Oxides with a lower oxidation number become more stable (from top to bottom)

• Halides– All the elements of Group 14 form tetrahalides – only tin and lead form dihalides– The tetrahalides are covalent tetrahedral molecules whereas the

dihalides are best regarded as ionic

The Carbon Group

• Hydrides– the hydrides of carbon are the hydrocarbons (organic

compounds) – silicon forms a series of hydrides called the silanes, with the

general formula SinH2n+2

• Oxidation States and Ionization Energies– exist in two oxidation states, +2 and +4 – there is a steady increase in the stability of the +2 oxidation

state (top to bottom)– The elements in this group have four electrons in their

outermost shell, two s electrons and two p electrons– The first four ionization energies rise in a fairly even manner,

and the fifth ionization energy is very large, reflecting the removal of an electron from a filled level nearer to the nucleus

The Carbon Group• Industrial Information

– The industrial importance of carbon in petrochemicals is immense. These hydrocarbons are used extensively in almost all areas of modern civilization.

• clothing, dyes, fertilizers, agrochemicals, fuels and new materials

– Silicon also contributes to new technology in the silicon chip, which has revolutionized the computer and high-tech industries.

– Germanium is, like silicon, a semi-conductor used in similar devices, but it is less widely used.

– Tin and lead have more traditional industrial uses. • Tin is used as a coating for other metals to prevent

corrosion, such as in tin cans, but it is in alloys that tin is used most extensively.

• Lead is used in great quantities in storage batteries. It is also used in cable covering, for roofing in buildings and for radiation shielding.

Carbon

• Allotropes– the three relatively well-known allotropes of carbon are

amorphous carbon, graphite, and diamond– Once considered exotic, fullerenes are nowadays

commonly synthesized and used in research• they include buckyballs (fullerenes),carbon

nanotubes, carbon nanobuds and nanofibers. • Several other exotic allotropes have also been

discovered, such as lonsdaleite, glassy carbon, carbon nanofoam and linear acetylenic carbon.

• Carbon is the fourth most abundant chemical element in the universe– Carbon is abundant in the sun, stars, comets, and in the

atmospheres of most planets.

Carbon

• Isotopes of carbon are atomic nuclei that contain six protons plus a number of neutrons (varying from 2 to 16).

• Carbon has two stable, naturally occurring isotopes– The isotope carbon-12 (12C) forms 98.93% of the carbon

on Earth – Carbon-13 (13C) forms the remaining 1.07%.

• Carbon has two stable, naturally occurring isotopes• the isotope carbon-12 serves as the basis for atomic

weights according to IUPAC• Identification of carbon in NMR experiments is done with

the isotope 13C • The English name carbon comes from the Latin carbo for

coal and charcoal, and from hence also comes the French charbon, meaning charcoal.

Silicon• the most common metalloid• silicon makes up 25.7% of the Earth's crust and is the

second most abundant element in the crust • silicon is vital to the construction industry as a principal

constituent of natural stone, glass, concrete and cement• Silicon's greatest impact on the modern world's economy

and lifestyle has resulted from silicon wafers used as substrates in the manufacture of discrete electronic devices such as transistors, and in the development of integrated circuits such as computer chips

• Silicon is used to make alloys which have applications in automotive industries

• Silicon was first identified by Antoine Lavoisier in 1787 and was later mistaken by Humphry Davy in 1800 for a compound.

• In 1824, Berzelius, generally given credit for discovering the element silicon

Germanium• In 1869, Dmitri Mendeleev predicted its existence and some

of its properties based on its position on his periodic table and called the element eka-silicon

• Germanium is an important semiconductor material used in transistors and various other electronic devices.

• Germanium is an important semiconductor material used in transistors and various other electronic devices.

• It is finding a new use in nanowires. • Because germanium and gallium arsenide have very similar

lattice constants, germanium substrates can be used to make gallium arsenide solar cells

• Due to the similarity between silica (SiO2) and germanium dioxide (GeO2), the silica stationary phase in some gas chromatography columns can be replaced by GeO2.

• In recent years germanium has seen increasing use in precious metal alloys.

Tin• The Latin name stannum originally meant an alloy of silver and

lead, and came to mean 'tin' in the 4th century • Tin is the 49th most abundant element in the Earth's crust,

representing 2 ppm• This silvery, malleable poor metal is not easily oxidized in air and

is used to coat other metals to prevent corrosion• The first alloy used in large scale since 3000 BC was bronze, an

alloy of tin and copper• Tin is used by itself, or in combination with other elements for a

wide variety of useful alloys. – Tin has long been used as a solder in the form of an alloy with

lead, tin accounting for 5 to 70% w/w.

Lead• Lead is a soft, malleable poor metal• It is also counted as one of the heavy metals• Lead is used in building construction, lead-acid batteries,

bullets and shots, weights, as part of solders, pewters, fusible alloys and as a radiation shield

• Lead is a poisonous substance to animals. It damages the nervous system and causes brain disorders

• Lead's symbol Pb is an abbreviation of its Latin name plumbum for soft metals

• Metallic lead does occur in nature, but it is rare. Lead is usually found in ore with zinc, silver and (most abundantly) copper, and is extracted together with these metals.

• Lead compounds are used as a coloring element in ceramic glazes, notably in the colors red and yellow

• Lead is frequently used in polyvinyl chloride (PVC) plastic, which coats electrical cords

Ununquadium• is the temporary name of a radioactive chemical element

with the temporary symbol Uuq and atomic number 114• the nuclei of ununquadium is synthesized by cold fusion

reactions; artificially produced• The longest-lived isotope currently known is 289Uuq with a

half-life of ~2.6 s, although there is evidence for an isomer, 289bUuq, with a half-life of ~66 s, that would be one of the longest-lived nuclei in the superheavy element region

• Initial chemical studies have strongly indicated that ununquadium possesses non-'eka'-lead properties and appears to behave as the first superheavy element that portrays noble-gas-like properties due to relativistic effects

• However, more recent experiments using a different set-up have indicated that ununquadium might actually have metallic properties