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Understanding Nanotechnology Scales


The smallest particle of a substance that retains the chemical and physical properties of the substance and is composed of two or more atoms; a group of like or different atoms held together by chemical forces.

The smallest particle into which an element or a compound can be divided without changing its chemical and physical properties; a group of atoms that is held together chemically.

The smallest particle of a substance that retains all the properties of the substance and is composed of one or more atoms

A molecule is the smallest particle of a pure chemical substance that still retains its chemical composition and properties. A molecule consists of multiple atoms joined by shared pairs of electrons in a covalent bond. It may consist of atoms of the same chemical element, as with oxygen gas (O2), or of different elements, as with water vapor (H2O).

Abstractly, a single atom may be considered a molecule, as it is when referred to collectively with molecules of multiple atoms, but in practice the use of the word molecule is usually confined to chemical compounds, of multiple atoms.

Smallest identifiable unit into which a pure substance can be divided and retain its composition and chemical properties.

Division into still smaller parts, eventually atoms, involves destroying the bonding that holds the molecule together.

For noble gases, the molecule is a single atom; all other substances have two (diatomic) or more (polyatomic) atoms in a molecule.

The atoms are the same in elements, such as hydrogen (H2), and different in compounds, such as glucose (C6H12O6).
Atoms always combine into molecules in fixed proportions. Molecules of different substances can have the same constituent atoms, either in different proportions, as in carbon monoxide (CO) and carbon dioxide (CO2), or bonded in different ways (see isomer).

The covalent bonds in molecules give them their shapes and most of their properties. (The concept of molecules has no significance in solids with ionic bonds.)


Greek nanos (with long "a"), nannos, little old man, dwarf, from nannas, meaning uncle.

A metric prefix meaning one billionth of a unit or 10-9.

A prefix meaning one billionth (1/1,000,000,000).

A prefix meaning one-billionth in the American numbering scheme, and one thousand millionth in the British system.


A nanometer is a unit of spatial measurement that is 10-9 meter, or one billionth of a meter.


One billionth of a second (10-9 seconds).

One thousandth of one millionth of a second.

Nanotechnology defined by NIST Physics laboratory:

"Nanotechnology is an emerging, interdisciplinary area of research with important commercial applications, and will, most assuredly, be a dominant technology in new-world economies.

As a general rule, nanotechnology addresses our ability to understand and manipulate the physical and technological characteristics that govern the behavior of a class of systems that possess at least one physical dimension that is (typically) on the order of 100 nm or less.

More importantly, perhaps, is that when this is the case, it is often observed that such systems may possess entirely new physical and chemical characteristics that result in properties that are neither well described by those of a single molecule of the substance, nor by those of the bulk material.

The new properties result from phenomena such as quantum confinement that occurs in the nanoscale dimensions, and in many instances the origins of the new properties are, at present, not fully understood.

Our ability to exploit these new properties for practical and useful gains lies in our ability to understand the underlying physics that governs them.

In addition, efforts are being made by the NIST to define a measurement system for nanotechnology. From the NIST website:

"Nanotechnology has tremendous potential to change the present paradigms in U.S. industry, including manufacturing, healthcare, materials, and electronics and communications, and it offers tremendous opportunities for enhancements to U.S. economic competitiveness.

Accordingly, NIST is focusing on the development of this technology's enabling infrastructure by developing critical measurement techniques and standards that are essential to the wide deployment of nanotechnology, including nanodevices, nanomagnetics, nanomanipulation and nanocharacterization.

As an example, in order to achieve high-volume production rates in the manufacture of nanoscale devices, it is essential that the physics governing self-assembly and self-replication be well understood.

Accurate and precise location of nanostructures and the measurement of the forces and kinetics that govern self-assembly are needed to permit efficacious implementation of any particular manufacturing strategy.

NIST is developing scanned-probe microscopy techniques that will permit detailed measurement of the physical, electronic, and magnetic properties of various classes of nanometer-scale structures, including quantum wires and dots.

Further, we are working on the method of autonomous atom assembly to fabricate atomically perfect nanostructures for scientific study."

Within the NIST Physics Laboratory, the principal scientific efforts in nanotechnology are being carried out within the Electron and Optical Physics Division and the Quantum Physics Division.

The work of these two groups is focused on developing a detailed understanding of the fundamental physical properties of nanometer-scale materials, and the technical challenges that must be overcome in order to synthesize useful quantities of nanomaterials and nanodevices for practical, industrial-scale applications.

Nanotechnology in the NIST Electron Physics Group: physics.nist.gov 1

Most of the research of the NIST Electron Physics Group is in Nanostructure Science or Nanotechnology.

Quantum Physics Division: physics.nist.gov 2


A unit of distance measure that equals 10-10 meters.

A unit of length equal to one ten-billionth of a meter

A unit of length equal to one hundred-millionth (10-8) of a centimeter, used especially to specify radiation wavelengths. Also called angstrom unit.

Micro - Prefix meaning one millionth.

Macro (macroscopic) - Large enough to be perceived or examined by the unaided eye.

However, macro meaning something seen by the naked eye is misleading. A view of earth taken by the Hubble Telescope is a "macro" view of earth, but certainly not one that can be seen by the human eye.

Macro, unlike micro, does not imply a specific unit of measurement. A micro is one millionth of something, whereas macro is a general term meaning anything larger than micro.


An element is a substance that is made entirely from one type of atom. For example, the element hydrogen is made from atoms containing a single proton and a single electron. If you change the number of protons an atom has, you change the type of element it is.

Some of the atoms in hydrogen have no neutrons, some of them have one neutron and a few of them have two neutrons. These different versions of hydrogen are called isotopes.

All isotopes of a particular element have the same number of protons, but have a different number of neutrons. If you change the number of neutrons an atom has, you make an isotope of that element.

There are 116 different elements. Some elements, like gold, silver, copper and carbon, have been known for centuries. Newer elements like meitnerium, darmstadtium and ununquadium are more recent.

All known elements are arranged on a chart called the Periodic Table of Elements.


The basic building block of all matter. The smallest particle of an element that has the same properties as the element. It consists of a central core called the nucleus that is made up of protons and neutrons. Electrons revolve in orbits in the region surrounding the nucleus.
A molecule is formed when two or more atoms join together chemically.

A compound is a molecule that contains at least two different elements.

All compounds are molecules but not all molecules are compounds.

An element is a substance that is made entirely from one type of atom. For example, the element hydrogen is made from atoms containing a single proton and a single electron. If you change the number of protons an atom has, you change the type of element it is.


Discovered by Ernest Rutherford in 1911, the nucleus is the central part of an atom. Composed of protons and neutrons, the nucleus contains most of an atom's mass.


Protons are positively charged particles found within atomic nuclei.

Ernest Rutherford discovered protons in experiments conducted between the years 1911 and 1919.

A stable, positively charged subatomic particle in the baryon family having a mass 1,836 times that of the electron.

A stable particle with positive charge equal to the negative charge of an electron.

Experiments done at the Stanford Linear Accelerator Center in the late 1960's and early 1970's showed that protons are made from other particles called quarks.
Protons are made from two 'up' quarks and one 'down' quark.


Neutrons are uncharged particles found within atomic nuclei. James Chadwick discovered neutrons in 1932.

Experiments done at the Stanford Linear Accelerator Center in the late 1960's and early 1970's showed that neutrons are made from other particles called quarks. Neutrons are made from one 'up' quark and two 'down' quarks.


Electrons are negatively charged particles that surround the atom's nucleus. J. J. Thomson discovered electrons in 1897.

The electron is the least massive electrically charged particle, therefore absolutely stable. It is the most common lepton with charge -1.

An electron is one of the fundamental particles in nature. Fundamental means that, as far as we know, an electron cannot be broken down into smaller particles (this concept is challenged by physicists looking for other particles).

Electrons are responsible for many of the phenomena that we observe in everyday life.

Mutual repulsion between electrons in the atoms of the floor and those within the shoes of a person's feet prevents the person from sinking and disappearing into the floor.

Electrons carry electrical current and successful manipulation of electrons allows electronic devices to function.

Electron Accelerator

Electrons carry electrical charge and successful manipulation of electrons allows electronic devices to function.

The picture and text on the video terminal in front of you is caused by electrons being accelerated and focused onto the inside of the screen, where a phosphor absorbs the electrons and light is produced.

A television screen is a simple, low-energy example of an electron accelerator.

A typical medical electron accelerator used in medical radiation therapy is about 1000 times more powerful than a color television set, while the electron accelerator is about 2,000,000 times more powerful than a color TV.


Quarks are believed to be one of the basic building blocks of matter.

Quarks were first discovered in experiments done at the Stanford Linear Accelerator Center in the late 1960's and early 1970's.

Three families of quarks are known to exist. Each family contains two quarks.
The first family consists of Up and Down quarks, the quarks that join together to form protons and neutrons.

The second family consists of Strange and Charm quarks and only exists at high energies.

The third family consists of Top and Bottom quarks and only exists at very high energies. The Top quark was finally discovered in 1995 at the Fermi National Accelerator Laboratory.

For more on quarks:

Stanford Linear Accelerator Center: www2.slac.stanford.edu

Sub-Atomic Particle

Any of various units of matter below the size of an atom, including the elementary particles and hadrons.

A particle that is less complex than an atom; regarded as constituents of all matter [syn: elementary particle, fundamental particle]

Elementary Particle

A knoblike body that appears on the luminal surfaces of mitochondrial cristae and is believed to be involved with the electron transport system.

Any of the subatomic particles that compose matter and energy, especially one hypothesized or regarded as an irreducible constituent of matter. Also called fundamental particle.


Any of a class of subatomic particles that are composed of quarks and take part in the strong interaction.

Any particle made of quarks and gluons, i.e. a meson or a baryon. All such particles have no strong charge (i.e are strong charge neutral objects) but participate in residual strong interactions due to the strong charges of their constituents.

Hadrons are colourless objects that consist of three quarks of different colour (baryons), or of a quark-antiquark pair (mesons).


The carrier particle of the strong interaction. There are 8 different gluons with colour charge 2, i.e. the gluons are by themselves strongly interacting particles. Gluons bind quarks inside proton and other hadrons.


A hadron with the basic structure of one quark and one antiquark.

Mesons are color-neutral particles with a basic structure of one quark and one antiquark. There are no stable mesons. Mesons have integer (or zero) units of spin, and hence are bosons, which means that they do not obey Pauli exclusion principle rules.
For more on mesons, see:
Stanford Linear Accelerator Center: www2.slac.stanford.edu


A hadron made from a basic structure of three quarks. The proton and the neutron are both baryon. The antiproton and the antineutron are antibaryons.

The proton is the only baryon that is stable in isolation. Its basic structure is two up quarks and one down quark.

Neutrons are also baryons. Although neutrons are not stable in isolation, they can be stable inside certain nuclei. A neutron's basic structure is two down quarks and one up quarks.

Strong Interaction

The interaction responsible for binding quarks and gluons to make hadrons. Residual strong interactions provide the nuclear binding force. In nuclear physics the term strong interaction is also used for this residual effect. (As a parallel, the force between electrically charged particles is an electromagnetic interaction, the force between neutral atoms that leads to the formation of molecules is a residual electromagnetic effect.)


A process in which a particle decays or it responds to a force due to the presence of another particle (as in a collision).

Atomic particle, atom, or chemical radical bearing an electrical charge, either negative or positive.

The process by which a neutral atom or molecule acquires a positive or negative charge.

Any process in which a particle disappears and in its place two or more different particles appear.

Forces and Interactions
All forces between objects are due to interactions. All particle decays are due to interactions. The four types fundamental interaction processes responsible for all observed processes are:

Strong interactions, responsible for forces between quarks and gluons and nuclear binding.

Electromagnetic interactions, responsible for electric and magnetic forces.
Weak interactions, responsible for the instability of all but the least massive fundamental particles in any class.

Gravitational interactions, responsible for forces between any two objects due to their energy (which, of course, includes their mass).

The Standard Model

The Standard Model is the name given to the current theory of fundamental particles and how they interact. This theory includes:

Strong interactions due to the color charges of quarks and gluons.

A combined theory of weak and electromagnetic interaction, known as electroweak theory, that introduces W and Z bosons as the carrier particles of weak processes, and photons as mediators to electromagnetic interactions.

The theory does not include the effects of gravitational interactions. These effects are tiny under high-energy Physics situations, and can be neglected in describing the experiments.

A theory that also includes a correct quantum version of gravitational interactions has not yet been achieved.

The Standard Model is a well-established theory applicable over a wide range of conditions.


A fundamental particle with neutral charge and near-zero mass supposedly produced in massive numbers by the nuclear reactions in stars; they are very hard to detect since the vast majority of them pass completely through the Earth without interacting.

A lepton with no electric charge. Neutrinos participate only in weak and gravitational interactions and are therefore very difficult to detect. There are three known types of neutrinos (electron-, muon- and tau-neutrino), one for each family of elementary particles,all of which are very light but could have a non-zero mass as indicated e.g. by the solar neutrino deficit.


A fundamental matter particle that does not participate in strong interactions. The charge leptons are the electron, the muon, the tau and their antiparticles. Neutral leptons are called neutrinos.


The carrier particle of the electromagnetic interaction.

Depending on its frequency (and therefore its energy) photons can have different names such as visible light, X rays and gamma rays.
We describe light in several ways. When we talk about "photons" we generally think of uncharged particles with out mass that carry energy (there are other similar kinds of particles).

Photons of light are known by other names such as gamma rays and x-rays.

Low-energy forms are called ultraviolet rays, infrared rays, and radio waves.

A photon is one of the fundamental particle in nature and it plays an important role involving electron interactions.

Photons are the most familiar particles in everyday existence. Light, radiant heat and microwaves make use of photons of different energies. An x-ray is a name given to the most energetic of these particles.

Cell (in biology)

The smallest structural unit of living organisms that is able to grow and reproduce independently.

Basic unit of any living organism. It is a small, watery compartment filled with chemicals and a complete copy of the organism's genome.

The human body is composed of trillions of cells; bacteria are a single cell.

Smallest unit of life (single cell organism or bacteria) or unit of higher organisms, i.e., multicellular organisms.

Cells are surrounded by a cell membrane (and cell wall in bacteria and plants = a membrane plus some chemically more stable structures, often mixtures of proteins and polysaccharides) and contain all necessary elements to sustain life; proteins, nucleic acids, lipids, minerals, and a diverse class of metabolites.

Cells of higher organisms (known as eukaryotes) are subdivided into subcellular compartments called organelles such as the mitochondrion, the cell nucleus, the endoplasmatic reticulum, the Golgi apparatus and many smaller organelles with highly specialized functions.

While all these organelles are found in animal cells, plant cells in addition contain a central vacuole that controls pressure to stabilize the cell and chloroplasts, the site of photosynthesis or light depended biosynthesis of sugars (carbohydrates).


The international standard unit of length, approximately equivalent to 39.37 inches. It was redefined in 1983 as the distance traveled by light in a vacuum in 1/299,792,458 of a second.

Yoctometer - 10 to the -24th power
Nanometer - 10 to the 9th power
Kilometer - 1000 meters
Yottameter - 10 to the 24th power meter

The everyday metric system

1000 millimeters = 1 meter
100 centimeters = 1 meter
1000 meters = 1 kilometer

Mass (or weight):
1000 milligrams = 1 gram
1000 grams = 1 kilogram
1000 kilograms = 1 metric ton

1000 milliliters = l liter
1000 liters = 1 cubic meter

10 000 square meters = 1 hectare
100 hectares = 1 square kilometer
Micro means 1/1 000 000
Milli- means 1/1000
Centi- means 1/100
Kilo- means 1000
Mega- means 1 000 000

m for meter
mm for millimeter
cm for centimeter
km for kilometer
g for gram
mg for milligram
kg for kilogram
L for liter
mL for milliliter
m2 for square meter
m3 for cubic meter
km2 for square kilometer
t for metric ton
ha for hectare

Some special relationships:
1 milliliter = 1 cubic centimeter
1 milliliter of water has a mass of approximately 1 gram
1 liter of water has a mass of approximately 1 kilogram
1 cubic meter of water has a mass of approximately 1 metric ton

Legal/official (exact) definitions of inch-pound units as set by U.S. law:
1 inch = 25.4 millimeters
1 pound = 453.59237 grams
1 gallon = 3.785411784 liters

Note: In Canada the inch and the pound are defined identically, but 1 Canadian gallon = 4.54609 liters.

Approximate conversion factors between inch-pound units and the International System of Units (SI):

Multiply inches by 2.54 to get centimeters (this conversion factor is exact)

Multiply feet by 0.305 to get meters
Multiply miles by 1.6 to get kilometers

Divide pounds by 2.2 to get kilograms

Multiply ounces by 28 to get grams

Multiply fluid ounces by 30 to get milliliters

Multiply gallons by 3.8 to get liters

Quantities and Units, General

A quantity in the general sense:is a property ascribed to phenomena, bodies, or substances that can be quantified for, or assigned to, a particular phenomenon, body, or substance. Examples are mass and electric charge.

A quantity in the particular sense:
is a quantifiable or assignable property ascribed to a particular phenomenon, body, or substance. Examples are the mass of the moon and the electric charge of the proton.

A physical quantity:
is a quantity that can be used in the mathematical equations of science and technology.

A unit:is a particular physical quantity, defined and adopted by convention, with which other particular quantities of the same kind are compared to express their value.

The value of a physical quantity:
is the quantitative expression of a particular physical quantity as the product of a number and a unit, the number being its numerical value. Thus, the numerical value of a particular physical quantity depends on the unit in which it is expressed.

SI base units

Definitions of the 7 SI base units (symbol in parenthesis)

Unit of length: Meter (m)
The meter is the length of the path traveled by light in vacuum during a time interval of 1/299 792 458 of a second.

Unit of mass: Kilogram (kg)
The kilogram is the unit of mass; it is equal to the mass of the international prototype of the kilogram.

Unit of time: Second (s)
The second is the duration of 9 192 631 770 periods of the radiation corresponding to the transition between the two hyperfine levels of the ground state of the cesium 133 atom.
Unit of electric current: Ampere (A)
The ampere is that constant current which, if maintained in two straight parallel conductors of infinite length, of negligible circular cross-section, and placed 1 meter apart in vacuum, would produce between these conductors a force equal to 2 x 10-7 newton per meter of length.

Unit of thermodynamic temperature:
Kelvin (K)
The kelvin, unit of thermodynamic temperature, is the fraction 1/273.16 of the thermodynamic temperature of the triple point of water.

Unit of amount of substance: Mole (mol)
1. The mole is the amount of substance of a system that contains as many elementary entities as there are atoms in 0.012 kilogram of carbon 12; its symbol is "mol."

2. When the mole is used, the elementary entities must be specified and may be atoms, molecules, ions, electrons, other particles, or specified groups of such particles.

Unit of luminous intensity: Candela (cd)
The candela is the luminous intensity, in a given direction, of a source that emits monochromatic radiation of frequency 540 x 1012 hertz and that has a radiant intensity in that direction of 1/683 watt per steradian.

For a detailed discussion and view of measurements see the following: National Institute of Standards and Technology (NIST) - Physics Laboratory: physics.nist.gov 3

NIST - Technology Services - Weights and Measures: physics.nist.gov 4

A Dictionary of Units www.ex.ac.uk

Size Comparisons:


Contains a flash animation comparing the size of an ordinary pin magnified 10, 100, 1000, 10,000, 100,000 and 1,000,000 times. www.cellsalive.com/howbig.htm

Molecular Expressions

Contains a flash animation starting with the Milky Way at 10 million light years from earth, moving exponentially through sub-atomic particles to the smallest particle known, the quark. micro.magnet.fsu.edu

Department of Energy (DOE) - Office of Basic Energy Sciences - The Scale of Things

Provides graphics illustrating the size of things ranging from an ant to nanotubes. www.science.doe.gov

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