Terminology


Allotropes
Some elements exist in several different structural forms, these are called allotropes.


For more information on Murray Robertson’s image see Uses and properties facts below.

 

Fact box terminology


Group
Elements appear in columns or ‘groups’ in the periodic table. Members of a group typically have similar properties and electron configurations in their outer shell.


Period
Elements are laid out into rows or ‘periods’ so that similar chemical behaviour is observed in columns.


Block
Elements are organised into blocks by the orbital type in which the outer electrons are found. These blocks are named for the characteristic spectra they produce: sharp, principal, diffuse, and fundamental.


Atomic Number
The number of protons in the nucleus.


Atomic Radius/non -bonded (Å)
based on Van der Waals forces (where several isotopes exist, a value is presented for the most prevalent isotope). These values were calculated using a multitude of methods including crystallographic data, gas kinetic collision cross sections, critical densities, liquid state properties, for more details please refer to the CRC Handbook of Chemistry and Physics.


Electron Configuration
The arrangements of electrons above the last (closed shell) noble gas.


Isotopes
Elements are defined by the number of protons in its centre (nucleus), whilst the number of neutrons present can vary. The variations in the number of neutrons will create elements of different mass which are known as isotopes.


Melting Point (oC)
The temperature at which the solid-liquid phase change occurs.


Melting Point (K)
The temperature at which the solid-liquid phase change occurs.


Melting Point (oF)
The temperature at which the solid-liquid phase change occurs.


Boiling Point (oC)
The temperature at which the liquid-gas phase change occurs.


Boiling Point (K)
The temperature at which the liquid-gas phase change occurs.


Boiling Point (oF)
The temperature at which the liquid-gas phase change occurs.


Sublimation
Elements that do not possess a liquid phase at atmospheric pressure (1 atm) are described as going through a sublimation process.


Density (g cm-3)
Density is the mass of a substance that would fill 1 cm3 at room temperature.


Relative Atomic Mass
The mass of an atom relative to that of Carbon-12. This is approximately the sum of the number of protons and neutrons in the nucleus. Where more than one isotope exists the value given is the abundance weighted average.


Key Isotopes (% abundance)
An element must by definition have a fixed number of protons in its nucleus, and as such has a fixed atomic number, however variants of an element can exist with differing numbers of neutrons, and hence a different atomic masses (e.g. 12C has 6 protons and 6 neutrons and 13C has 6 protons and 7 neutrons).


CAS number
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 (where several isotopes exist, a value is presented for the most prevalent isotope).

Fact box

 
Group 13  Melting point 2077 oC, 3771 oF, 2350 K 
Period Boiling point 4000 oC, 7232 oF, 4273 K 
Block Density (g cm-3) 2.34 
Atomic number Relative atomic mass 10.81  
State at 20°C Solid  Key isotopes 11
Electron configuration [He] 2s22p1  CAS number 7440-42-8 
ChemSpider ID 4575371 ChemSpider is a free chemical structure database
 

Uses and properties terminology


Image Explanation

Murray Robertson is the artist behind the images which make up Visual Elements. This is where the artist explains his interpretation of the element and the science behind the picture.


Natural Abundance

Where this element is most commonly found in nature.


Biological Roles

The elements role within the body of humans, animals and plants. Also functionality in medical advancements both today and years ago.


Appearance

The description of the element in its natural form.

Uses and properties

 
Image explanation

An image reflecting the importance of boron as an essential mineral for plants. The tree and its strange metallic foliage ‘grow’ from a ‘pure’ dark powdered cone of the element.

Appearance

Pure boron is a dark amorphous powder.

Uses

Amorphous boron is used as a rocket fuel igniter and in pyrotechnic flares. It gives the flares a distinctive green colour.

The most important compounds of boron are boric (or boracic) acid, borax (sodium borate) and boric oxide. These can be found in eye drops, mild antiseptics, washing powders and tile glazes. Borax used to be used to make bleach and as a food preservative.

Boric oxide is also commonly used in the manufacture of borosilicate glass (Pyrex). It makes the glass tough and heat resistant. Fibreglass textiles and insulation are made from borosilcate glass.

Sodium octaborate is a flame retardant.

The isotope boron-10 is good at absorbing neutrons. This means it can be used to regulate nuclear reactors. It also has a role in instruments used to detect neutrons.

Biological role

Boron is essential for the cell walls of plants. It is not considered poisonous to animals, but in higher doses it can upset the body’s metabolism. We take in about 2 milligrams of boron each day from our food, and about 60 grams in a lifetime. Some boron compounds are being studied as a possible treatment for brain tumours.

Natural abundance

Boron occurs as an orthoboric acid in some volcanic spring waters, and as borates in the minerals borax and colemanite. Extensive borax deposits are found in Turkey. However, by far the most important source of boron is rasorite. This is found in the Mojave Desert in California, USA.

High-purity boron is prepared by reducing boron trichloride or tribromide with hydrogen, on electrically heated filaments. Impure, or amorphous, boron can be prepared by heating the trioxide with magnesium powder.

 
Atomic data terminology

Atomic radius/non -bonded (Å)
Based on Van der Waals forces (where several isotopes exist, a value is presented for the most prevalent isotope). These values were calculated using a multitude of methods including crystallographic data, gas kinetic collision cross sections, critical densities, liquid state properties,for more details please refer to the CRC Handbook of Chemistry and Physics.


Electron affinity (kJ mol-1)
The energy released when an additional electron is attached to the neutral atom and a negative ion is formed (where several isotopes exist, a value is presented for the most prevalent isotope). *


Electronegativity (Pauling scale)
The degree to which an atom attracts electrons towards itself, expressed on a relative scale as a function bond dissociation energies, Ed in eV. χA - χB =(eV)-1/2sqrt(Ed(AB)-[Ed(AA)+Ed(BB)]/2), with χH set as 2.2 (where several isotopes exist, a value is presented for the most prevalent isotope).


1st Ionisation energy (kJ mol-1)
The minimum energy required to remove an electron from a neutral atom in its ground state (where several isotopes exist, a value is presented for the most prevalent isotope).


Covalent radius (Å)
The size of the atom within a covalent bond, given for typical oxidation number and coordination (where several isotopes exist, a value is presented for the most prevalent isotope). ***

Atomic data

 
Atomic radius, non-bonded (Å) 1.92 Covalent radius (Å) 0.84
Electron affinity (kJ mol-1) 26.989 Electronegativity
(Pauling scale)
2.04
Ionisation energies
(kJ mol-1)
 
1st
800.637
2nd
2427.069
3rd
3659.751
4th
25025.905
5th
32826.802
6th
-
7th
-
8th
-
 

Mining/Sourcing Information

Data for this section of the data page has been provided by the British Geological Survey. To review the full report please click here or please look at their website here.


Key for numbers generated


Governance indicators

1 (low) = 0 to 2

2 (medium-low) = 3 to 4

3 (medium) = 5 to 6

4 (medium-high) = 7 to 8

5 (high) = 9


Reserve distribution (%)

1 (low) = 0 to 30 %

2 (medium-low) = 30 to 45 %

3 (medium) = 45 to 60 %

4 (medium-high) = 60 to 75 %

5 (high) = 75 %

(Where data are unavailable an arbitrary score of 2 was allocated. For example, Be, As, Na, S, In, Cl, Ca and Ge are allocated a score of 2 since reserve base information is unavailable. Reserve base data are also unavailable for coal; however, reserve data for 2008 are available from the Energy Information Administration (EIA).)


Production Concentration

1 (low) = 0 to 30 %

2 (medium-low) = 30 to 45 %

3 (medium) = 45 to 60 %

4 (medium-high) = 60 to 75 %

5 (high) = 75 %


Crustal Abundance

1 (low) = 100 to 1000 ppm

2 (medium-low) =10 to 100 ppm

3 (medium) = 1 to 10 ppm

4 (medium-high) = 0.1 to 1 ppm

5 (high) = 0.1 ppm

(Where data are unavailable an arbitrary score of 2 was allocated. For example, He is allocated a score of 2 since crustal abundance data is unavailable.)


Explanations for terminology


Crustal Abundance (ppm)

The abundance of an element in the Earth's crust in parts-per-million (ppm) i.e. The number of atoms of this element per 1 million atoms of crust.


Sourced

The country with the largest reserve base.


Reserve distribution (%)

This is a measure of the spread of future supplies, recording the percentage of a known resource likely to be available in the intermediate future (reserve base) located in the top three countries.


Production Concentrations

This reports the percentage of an element produced in the top three countries. The higher the value, the larger risk there is to supply.


Political stability of top producer

The World Bank produces a global percentile rank of political stability. The scoring system is given below, and the values for all three production countries were summed.


Relative Supply Risk Index

The Crustal Abundance, Reserve distribution (%), Production Concentration and Governance Factor scores are summed and then divided by 2, to provide an overall Relative Supply Risk Index.

Supply risk

 
Relative supply risk 4.5
Crustal abundance (ppm) 11
Recycling rate (%) Unknown
Substitutability Unknown
Production concentration (%) 33.6
Reserve distribution (%) Unknown
Top 3 producers
  • 1) Turkey
  • 2) USA
  • 3) Chile
Top 3 reserve holders
  • 1) Turkey
  • 2) Russia
  • 3) USA
Political stability of top producer 11.8
Political stability of top reserve holder 11.8
 

Oxidation states and isotopes


Key for Isotopes


Half Life
  y years
  d days
  h hours
  m minutes
  s seconds
Mode of decay
  α alpha particle emission
  β negative beta (electron) emission
  β+ positron emission
  EC orbital electron capture
  sf spontaneous fission
  ββ double beta emission
  ECEC double orbital electron capture

Terminology


Common Oxidation states
The oxidation state of an atom is a measure of the degree of oxidation of an atom. It is defined as being the charge that an atom would have if all bonds were ionic. Free atoms have an oxidation state of 0, and the sum of oxidation numbers within a substance must equal the overall charge.


Important Oxidation states
The most common oxidation states of an element in its compounds.


Isotopes
Elements are defined by the number of protons in its centre (nucleus), whilst the number of neutrons present can vary. The variations in the number of neutrons will create elements of different mass which are known as isotopes.

Oxidation states and isotopes

 
Common oxidation states 3
Isotopes Isotope Atomic mass Natural abundance (%) Half life Mode of decay
  10B 10.013 19.9
  11B 11.009 80.1
 

Pressure and temperature - advanced terminology


Specific heat capacity (J kg-1 K-1)

Specific heat capacity is the amount of energy needed to change the temperature of a kilogram of a substance by 1 K.


Young's modulus (GPa)

Young's modulus is a measure of the stiffness of a substance, that is, it provides a measure of how difficult it is to extend a material, with a value given by the ratio of tensile strength to tensile strain.


Shear modulus (GPa)

The shear modulus of a material is a measure of how difficult it is to deform a material, and is given by the ratio of the shear stress to the shear strain.


Bulk modulus (GPa)

The bulk modulus is a measure of how difficult to compress a substance. Given by the ratio of the pressure on a body to the fractional decrease in volume.


Vapour Pressure (Pa)

Vapour pressure is the measure of the propensity of a substance to evaporate. It is defined as the equilibrium pressure exerted by the gas produced above a substance in a closed system.

Pressure and temperature data – advanced

 
Specific heat capacity
(J kg-1 K-1)
1026 Young's modulus (GPa) Unknown
Shear modulus (GPa) Unknown Bulk modulus (GPa) Unknown
Vapour pressure  
Temperature (K)
400 600 800 1000 1200 1400 1600 1800 2000 2200 2400
Pressure (Pa)
- - - - - - - - - - -
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History

For centuries the only source of borax, Na2B2O5(OH)4, was the crystallized deposits of Lake Yamdok Cho, in Tibet. It was used as a flux used by goldsmiths.


In 1808, Louis-Josef Gay-Lussac and Louis-Jacques Thénard working in Paris, and Sir Humphry Davy in London, independently extracted boron by heating borax  with potassium metal. In fact, neither had produced the pure element which is almost impossible to obtain. A purer type of boron was isolated in 1892 by Henri Moissan. Eventually, E. Weintraub in the USA produced totally pure boron by sparking a mixture of boron chloride, BCl3 vapour, and hydrogen. The material so obtained boron was found to have very different properties to those previously reported.

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Podcasts

Listen to Boron Podcast
Transcript :

Chemistry in Its Element - Boron


  (Promo)

 

You're listening to Chemistry in its element brought to you by Chemistry World, the magazine of the Royal Society of Chemistry

(End promo)

 

Meera Senthilingam

 

This week we see the true nature of an element wrongly accused of being boring.   I'm Meera Senthilingam from the Naked Scientists.com, and to see how a supposed dreary element can indulge in swinging antics and numerous adventures here's Pat Bailey with the brighter side of Boron.

 

Pat Bailey

 

If I had to choose a person to represent gold, then I guess it might be an ambitious young stockbroker, a bit flashy, and not great at forming relationships.   For helium - an airy-fairy blonde with a bit of a squeaky voice, but with aspirations to join the nobility.

 

And for boron?   Well at first glance, during the working week at any rate, a boring, middle-aged accountant, maybe wearing brown corduroys and a tweed jacket . but with an unexpected side-to him in his spare time - skydiving, motorbiking, and a member of a highly dubious society that indulges in swapping partners.

 

Let's start with the boring bit.   Boron is usually isolated as a brown, amorphous solid.   I don't know anyone who thinks the element boron has anything interesting about it.   But its unexpected side starts to emerge when you look at some simple compounds of boron.   Consider the nitride, for example - just the 2 elements at numbers 5 and 7 in the periodic table, but able to join forces to provide hard diamond or soft graphite-like structures, very similar to those of the 6th element, carbon.   Then there is the trifluoride - remember that acids were first classified as substances that could provide protons, but BF3 is the archetypal Lewis acid, which doesn't have a proton in sight, yet is able to coordinate with lone pairs, allowing it to catalyse an array of reactions.   It can achieve this chemistry because boron really does have two sides to it - it is set up to form 3 bonds with adjacent atoms, but even in this state, readily forms an extra bond in order to complete the 2nd main shell of 8 electrons . but when it does this, it acquires a negative charge, and it can only regain neutrality by losing one of its bonds - it really does have a split personality.

 

But the real interest, the 'skydiving', starts when we look at the trihydride of boron.   We'll return to this later on, as BH3 has structural subtleties that will really take us into sexy territory.   But at this stage we'll simply see how boron's schizophrenic side can be used to good effect - add BH3 to an alkene, then throw in some alkaline hydrogen peroxide, and the oxygen first attaches to the boron, and then gets shuttled onto the adjacent carbon, all driven by this balance between 3- and 4-valent boron.   This rather complicated reaction (mechanistically) is very reliable, and has been used for decades now as a simple way of turning alkenes into alcohols.   Building on this idea, lots of clever variants allow one to introduce the alcohol very selectively, including my favourite of the reagent made by reacting borane with cycloocta-1,5-diene; the resulting dialkylborane is incredibly selective at attacking only the least substituted carbon of an alkene, and its often abbreviated schematically to a BH unit hanging down from two arcs, leading to its nickname as the parachute molecule.

 

So much for skydiving - what about motorbikes.   Well this bit is rather like seeing what appears to be a 50cc moped, only to find that it goes from 0-to-60 in 3.5 seconds.   Let me explain - the name boron comes from the mineral borax, which is a salt of the a really uninspiring acid called boracic acid.   You can buy it from any pharmacist, and it's a mildly acidic antiseptic, and it essentially comprises a boron atom attached to three OH groups.   And here's the surprise - you can fairly easily swap one OH for an aryl group, and you generate an aryl boronic acid capable of coupling to a whole range of aryl halides using palladium catalysis.   This was a long sought-after process that many had thought impossible in high yield, until a chemist called Suzuki (hence the motorbike connection) found that boron could solve the trick.

 

And lastly to the sexy bit.   I said that boron trihydride had a structural subtlety, and that is the fact that it was an 'impossible' molecule back in 1945, in that there was no known bonding that could account for its dimeric structure, or that of some related boron hydrides.   And then in one of those 'Just William' sort of stories when a youngster gets the better of his elders, Christopher Longuet-Higgins, then an undergraduate at Cambridge, came up with the solution during a tutorial, publishing the landmark paper with his tutor whilst still only 20.   Their explanation also predicted several new boron hydrides, which were duly discovered, as well as the fascinating field of boron cluster chemistry, in which the tri/tetra-valent schizophrenia of boron allows partner swaps and multiple bonding . but I won't elaborate further - you'll have to find out for yourself.   But remember, don't just judge elements by their first appearance - they may have hidden secrets and unexpected talents.

 

Meera Senthilingam

 

So, split personalities, parachute molecules, and swapping partners - I certainly won't be judging this element on its first appearance.   That was Keele University's Pat Bailey revealing the truth about Boron.   Now, next time we meet an element that also believes in humility.

 

Brian Clegg

 

When it comes to use lanthanum best resembles a successful movie bit part player. Someone who never gets the lead role, but appears in film after film, solidly portraying different characters. Not a particularly expensive material to produce, lanthanum's many roles remain of a supporting kind, playing an essential part but avoiding the limelight.

 

Meera Senthilingam

 

Join Brian Clegg to find out how the humble lanthanum spreads itself around town in next week's Chemistry in its Element.   Until then, thank you for listening, I'm Meera Senthilingam from the Naked Scientists.com.

 

   (Promo)

 

Chemistry in its element is brought to you by the Royal Society of Chemistry and produced by thenakedscientists dot com. There's more information and other episodes of Chemistry in its element on our website at chemistryworld dot org forward slash elements. 

 

(End promo)

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Resources

Description :
A series of short screencasts to introduce the Chemistry of selected Elements These come from this website: http://www.chemistryvignettes.net/
Description :
This experiment illustrates the displacement of copper from copper(II) sulfate solution using aluminium foil.
Description :
We discover how to extract lead from lead(II) oxide. We mix lead(II) oxide with charcoal powder and then heat the mixture using a Bunsen burner. It glows bright red as a reaction occurs and after a fe...
Learn Chemistry: Your single route to hundreds of free-to-access chemistry teaching resources.
 

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References

 
Images:  Visual Elements © Murray Robertson 2011
Mining and Sourcing data:  British Geological Survey – natural environment research council.
Text:  John Emsley Nature’s Building Blocks: An A-Z Guide to the Elements, Oxford University Press, 2nd Edition, 2011.
Additional information for platinum, gold, neodymium and dysprosium obtained from Material Value Consultancy Ltd www.matvalue.com
Data: CRC Handbook of Chemistry and Physics, CRC Press, 92nd Edition, 2011.
G. W. C. Kaye and T. H. Laby Tables of Physical and Chemical Constants, Longman, 16th Edition, 1995.
Members of the RSC can access these books through our library.