3D (left and center) and 2D (right) representations of the terpenoid molecule atisane

A molecule ( /ˈmɒlɪkjuːl/) is an electrically neutral group of two or more atoms held together by covalent chemical bonds.^{[1][2][3][4][5][6]} Molecules are distinguished from ions by their lack of electrical charge. However, in quantum physics, organic chemistry, and biochemistry, the term molecule is often used less strictly, also being applied to polyatomic ions.

In the kinetic theory of gases, the term molecule is often used for any gaseous particle regardless of its composition. According to this definition noble gas atoms are considered molecules despite the fact that they are composed of a single non-bonded atom.^[7]

A molecule may consist of atoms of a single chemical element, as with oxygen (O₂), or of different elements, as with water (H₂O). Atoms and complexes connected by non-covalent bonds such as hydrogen bonds or ionic bonds are generally not considered single molecules.^[8]

Molecules as components of matter are common in organic substances (and therefore biochemistry). They also make up most of the oceans and atmosphere. However, the majority of familiar solid substances on Earth, including most of the minerals that make up the crust, mantle, and core of the Earth, contain many chemical bonds, but are not made of identifiable molecules. Also, no typical molecule can be defined for ionic crystals (salts) and covalent crystals (network solids), although these are often composed of repeating unit cells that extend either in a plane (such as in graphene) or three-dimensionally (such as in diamond, quartz, or sodium chloride). The theme of repeated unit-cellular-structure also holds for most condensed phases with metallic bonding, which means that solid metals are also not made of molecules. In glasses (solids that exist in a vitreous disordered state), atoms may also be held together by chemical bonds without presence of any definable molecule, but also without any of the regularity of repeating units that characterises crystals.

Molecular science[link]

The science of molecules is called molecular chemistry or molecular physics, depending on the focus. Molecular chemistry deals with the laws governing the interaction between molecules that results in the formation and breakage of chemical bonds, while molecular physics deals with the laws governing their structure and properties. In practice, however, this distinction is vague. In molecular sciences, a molecule consists of a stable system (bound state) comprising two or more atoms. Polyatomic ions may sometimes be usefully thought of as electrically charged molecules. The term unstable molecule is used for very reactive species, i.e., short-lived assemblies (resonances) of electrons and nuclei, such as radicals, molecular ions, Rydberg molecules, transition states, van der Waals complexes, or systems of colliding atoms as in Bose-Einstein condensate

History and etymology[link]

John Dalton

According to Merriam-Webster and the Online Etymology Dictionary, the word "molecule" derives from the Latin "moles" or small unit of mass.

• Molecule (1794) – "extremely minute particle," from Fr. molécule (1678), from Mod.L. molecula, dim. of L. moles "mass, barrier". A vague meaning at first; the vogue for the word (used until late 18th century only in Latin form) can be traced to the philosophy of Descartes.

Although the existence of molecules has been accepted by many chemists since the early 19th century as a result of Dalton's laws of Definite and Multiple Proportions (1803–1808) and Avogadro's law (1811), there was some resistance among positivists and physicists such as Mach, Boltzmann, Maxwell, and Gibbs, who saw molecules merely as convenient mathematical constructs. The work of Perrin on Brownian motion (1911) is considered to be the final proof of the existence of molecules.^{[citation needed]}

The definition of the molecule has evolved as knowledge of the structure of molecules has increased. Earlier definitions were less precise, defining molecules as the smallest particles of pure chemical substances that still retain their composition and chemical properties.^[9] This definition often breaks down since many substances in ordinary experience, such as rocks, salts, and metals, are composed of large networks of chemically bonded atoms or ions, but are not made of discrete molecules.

Molecular size[link]

Most molecules are far too small to be seen with the naked eye, but there are exceptions. DNA, a macromolecule, can reach macroscopic sizes, as can molecules of many polymers. The smallest molecule is the diatomic hydrogen (H₂), with a bond length of 0.74 Å.^[10] Molecules commonly used as building blocks for organic synthesis have a dimension of a few Å to several dozen Å. Single molecules cannot usually be observed by light (as noted above), but small molecules and even the outlines of individual atoms may be traced in some circumstances by use of an atomic force microscope. Some of the largest molecules are macromolecules or supermolecules.

Radius[link]

Effective molecular radius is the size a molecule displays in solution.^[11][12] The table of permselectivity for different substances contains examples.

Molecular formula[link]

A compound's empirical formula is the simplest integer ratio of the chemical elements that constitute it. For example, water is always composed of a 2:1 ratio of hydrogen to oxygen atoms, and ethyl alcohol or ethanol is always composed of carbon, hydrogen, and oxygen in a 2:6:1 ratio. However, this does not determine the kind of molecule uniquely – dimethyl ether has the same ratios as ethanol, for instance. Molecules with the same atoms in different arrangements are called isomers. Also carbohydrates, for example, have the same ratio (carbon:hydrogen:oxygen = 1:2:1) (and thus the same empirical formula) but different total numbers of atoms in the molecule.

The molecular formula reflects the exact number of atoms that compose the molecule and so characterizes different molecules. However different isomers can have the same atomic composition while being different molecules.

The empirical formula is often the same as the molecular formula but not always. For example, the molecule acetylene has molecular formula C₂H₂, but the simplest integer ratio of elements is CH.

The molecular mass can be calculated from the chemical formula and is expressed in conventional atomic mass units equal to 1/12 of the mass of a neutral carbon-12 (¹²C isotope) atom. For network solids, the term formula unit is used in stoichiometric calculations.

Molecular geometry[link]

Molecules have fixed equilibrium geometries—bond lengths and angles— about which they continuously oscillate through vibrational and rotational motions. A pure substance is composed of molecules with the same average geometrical structure. The chemical formula and the structure of a molecule are the two important factors that determine its properties, particularly its reactivity. Isomers share a chemical formula but normally have very different properties because of their different structures. Stereoisomers, a particular type of isomers, may have very similar physico-chemical properties and at the same time different biochemical activities.

Molecular spectroscopy[link]

Molecular spectroscopy deals with the response (spectrum) of molecules interacting with probing signals of known energy (or frequency, according to Planck's formula). Molecules have quantized energy levels that can be analyzed by detecting the molecule's energy exchange through absorbance or emission.^[13] Spectroscopy does not generally refer to diffraction studies where particles such as neutrons, electrons, or high energy X-rays interact with a regular arrangement of molecules (as in a crystal).

Theoretical aspects[link]

The study of molecules by molecular physics and theoretical chemistry is largely based on quantum mechanics and is essential for the understanding of the chemical bond. The simplest of molecules is the hydrogen molecule-ion, H₂⁺, and the simplest of all the chemical bonds is the one-electron bond. H₂⁺ is composed of two positively charged protons and one negatively charged electron, which means that the Schrödinger equation for the system can be solved more easily due to the lack of electron–electron repulsion. With the development of fast digital computers, approximate solutions for more complicated molecules became possible and are one of the main aspects of computational chemistry.

When trying to define rigorously whether an arrangement of atoms is "sufficiently stable" to be considered a molecule, IUPAC suggests that it "must correspond to a depression on the potential energy surface that is deep enough to confine at least one vibrational state".^[1] This definition does not depend on the nature of the interaction between the atoms, but only on the strength of the interaction. In fact, it includes weakly bound species that would not traditionally be considered molecules, such as the helium dimer, He₂, which has one vibrational bound state^[14] and is so loosely bound that it is only likely to be observed at very low temperatures.

See also[link]

Wikimedia Commons has media related to: Molecules

References[link]

External links[link]

• Molecule of the Month – School of Chemistry, University of Bristol

Martina Topley-Bird
Performing at Fri-Son, Fribourg, Switzerland (photo 6 November 2008)
Background information
Birth name	Martina Gillian Topley
Born	(1975-05-07) 7 May 1975 (age 37) St. Pancras, London, England
Genres	Pop, trip hop
Instruments	Vocals, keyboards, guitar, ukulele
Years active	1993–present
Labels	Independiente Honest Jon's
Associated acts	Tricky Massive Attack
Website	Official website

Performing at Rough Trade East, Brick Lane, London
(photo July 2010)

Martina Topley-Bird (born 7 May 1975, St. Pancras, London) is an English vocalist and songwriter who first gained fame as the featured female vocalist on trip hop pioneer Tricky's debut album, Maxinquaye (a printing error credited her as "Martine"). She worked with him on his follow-up albums and, in 2003, released her own solo album, Quixotic.

Biography[link]

The daughter of a well known advertising executive, Drayton Bird,Topley-Bird was educated at Clifton College where she sang in the choir.^[1] It was while she was a teenager at the school that she met trip hop pioneer Tricky, with whom she worked on his first album Maxinquaye.^[2] She continued her collaboration with Tricky on his follow-up albums Nearly God, Pre-Millennium Tension and Angels with Dirty Faces.

Following a falling-out of their professional and personal relationship in 1998, she began pursuing a solo career. It was not until 2003 that she released her debut album, Quixotic (Independiente Records), mainly produced by Topley-Bird and production team AMP9 (Alex McGowan, Steve Crittall, Nick Bird) at Space Eko Recording Studios London. Upon its release, it received positive reviews from critics and was a finalist for the 2003 Mercury Music Prize. The song "Sandpaper Kisses" from the album was featured in the video game, Fahrenheit (released in North America as Indigo Prophecy).

The album finally saw a limited release in the United States in July 2004 when the Palm Pictures label released a re-designed and re-sequenced version with a new title (Anything), a trimmed-down tracklisting and all-new cover art.

The following year she appeared on the Starbucks compilation album, Sweetheart 2005: Love Songs, which features contemporary musicians covering classic love songs. She sang "I Only Have Eyes for You", a song originally by composer Harry Warren and lyricist Al Dubin.

Her second solo album, The Blue God, was released in May 2008. The track "Carnies" was released as the first single on 3 March 2008^[3] and reached No.20 on the UK Indie Charts.^[4] "Poison" was released as the second single^[5] and reached No.9 on the Indie Charts.^[4]

In 2010, Topley-Bird appeared on the album Heligoland by Massive Attack, lending her voice on the tracks "Psyche" and "Babel". She also toured with Massive Attack as their support act and providing guest vocals. Topley-Bird's third album, Some Place Simple, was released in July 2010. It contained stripped-down versions of songs from her first two releases, along with four new songs.

Topley-Bird performed Maxinquaye live at the Sundance Festival, London, in April 2012.^[6]

Discography[link]

Albums[link]

• Quixotic (2003, Independiente) - UK #70,^[7] FR #58
• Anything (2004, Palm Pictures)
• The Blue God (2008, Independiente) - UK #88, FR #149
• Some Place Simple (2010, Honest Jon's) - SWI #60

Singles[link]

• 2003 "Need One"
• 2003 "Anything"
• 2003 "I Still Feel"
• 2004 "Soul Food"
• 2008 "Carnies"
• 2008 "Poison"
• 2008 "Baby Blue"

Collaborations[link]

• Topley-Bird is credited as a vocalist on "Conversing Among Misfits", a song from 1998 debut (self-titled) album by Earthlings?. Her performance is hard to hear in the final mix however.
• In 1999, she contributed vocals to "Dirty Drowning Man" and "Coattails of a Dead Man" on Primus's album Antipop.
• In 2000, Topley-Bird appeared on David Holmes's album Bow Down to the Exit Sign.
• In 2004, Topley-Bird appeared on "Into the Sun", a track from Diplo's album Florida.
• In 2004, Topley-Bird contributed vocals to "Spoiled", on the Blues Explosion's album Damage.
• In 2005, she made a guest appearance (alongside Roots Manuva) on the Gorillaz track "All Alone", on the album Demon Days. She also was featured in the unreleased Gorillaz song, "Snakes and Ladders", also with Roots Manuva.
• In 2005/2006,^[which?] Topley-Bird sang vocals for "Can't Be Serious" from A Mountain of One's debut 12" EP, later included on the group's 2007 Collected Works compilation.
• In 2006, Topley-Bird appeared on the song "Devil Take My Soul" on the Son of Dave record 02.
• Topley-Bird appears on the songs "Why Should I?" and "Deflect" on Leila's 2008 album, Blood, Looms and Blooms. "Deflect" was also the lead track on the pre-album EP Deflect.
• She contributes vocals on the Saturnalia album by The Gutter Twins ("The Body") (2008)
• In 2008, on her single "Poison", she collaborates again with Roots Manuva and Gorillaz on the B-side track "Soldier Boy".
• She makes an appearance on rapper Common's album Universal Mind Control, on a song entitled "Everywhere".
• In 2009, she sang and co-wrote "Psyche" and "Babel" by Massive Attack, for their 2010 album Heligoland
• In 2012, Topley-Bird appeared on "Open" and "Secret", two tracks from Clark's Iradelphic album.

Song appearances[link]

• "Need One" appears on the CSI: Miami episode "Blood Brothers" in 2003.
• "Need One" was used in a television advertisement for Toyota's Corolla Verso in 2004.
• "Sandpaper Kisses" appears on the soundtrack of the 2005 videogame Fahrenheit.
• In 2007, her song "Da Da Da Da" was used in the film Virgin Territory.
• "Need One" was featured in an advertisement for H&M on Swedish and Dutch television during autumn of 2008.
• "Ilya" was used in "Lap Dance", an episode from The L Word's second season.
• "Soul Food" was used in 2009 in the film Obsessed.
• "Sandpaper Kisses" was sampled by The Weeknd in The Birds Part 2, which is included in his second mixtape "Thursday"

References[link]

External links[link]

Wikimedia Commons has media related to: Martina Topley-Bird

• Official website
• Moon Palace (German fansite)
• "Girl interrupted" from The Observer Magazine, 25 May 2003
• Space Eko Recording Studio on Myspace
• Anything @ Palm Pictures