Related topics: nanometers · crystals

Graphene: The more you bend it, the softer it gets

New research by engineers at the University of Illinois combines atomic-scale experimentation with computer modeling to determine how much energy it takes to bend multilayer graphene—a question that has eluded scientists ...

Determining the shapes of atomic clusters

Too large to be classed as molecules, but too small to be bulk solids, atomic clusters can range in size from a few dozen to several hundred atoms. The structures can be used for a diverse range of applications, which requires ...

Chains of atoms move at lightning speed inside metals

A phenomenon that has previously been seen when researchers simulate the properties of planet cores at extreme pressures has now also been observed in pure titanium at atmospheric pressure. Chains of atoms dash around at ...

Physics vs. asthma

A research team from the MIPT Center for Molecular Mechanisms of Aging and Age-Related Diseases has collaborated with colleagues from the U.S., Canada, France, and Germany to determine the spatial structure of the CysLT1 ...

Scientists discover new antibiotic in tropical forest

Scientists from Rutgers University and around the world have discovered an antibiotic produced by a soil bacterium from a Mexican tropical forest that may help lead to a "plant probiotic," more robust plants and other antibiotics.

Molecular nanocarbons with mechanical bonds

Carbon materials with nano-scale periodicity such as graphene and carbon nanotubes, called "nanocarbons," are expected to become light, highly functional next-generation materials. There have been demands for precise synthesis ...

Researchers reveal molecular basis of vision

Researchers have solved the three-dimensional structure of a protein complex involved in vertebrate vision at atomic resolution, a finding that has broad implications for our understanding of biological signaling processes ...

How molecular footballs burst in an X-ray laser beam

An international research team has observed in real time how football molecules made of carbon atoms burst in the beam of an X-ray laser. The study shows the temporal course of the bursting process, which takes less than ...

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Atom

The atom is a basic unit of matter consisting of a dense, central nucleus surrounded by a cloud of negatively charged electrons. The atomic nucleus contains a mix of positively charged protons and electrically neutral neutrons (except in the case of hydrogen-1, which is the only stable nuclide with no neutron). The electrons of an atom are bound to the nucleus by the electromagnetic force. Likewise, a group of atoms can remain bound to each other, forming a molecule. An atom containing an equal number of protons and electrons is electrically neutral, otherwise it has a positive or negative charge and is an ion. An atom is classified according to the number of protons and neutrons in its nucleus: the number of protons determines the chemical element, and the number of neutrons determine the isotope of the element.

The name atom comes from the Greek ἄτομος/átomos, α-τεμνω, which means uncuttable, something that cannot be divided further. The concept of an atom as an indivisible component of matter was first proposed by early Indian and Greek philosophers. In the 17th and 18th centuries, chemists provided a physical basis for this idea by showing that certain substances could not be further broken down by chemical methods. During the late 19th and early 20th centuries, physicists discovered subatomic components and structure inside the atom, thereby demonstrating that the 'atom' was divisible. The principles of quantum mechanics were used to successfully model the atom.

Relative to everyday experience, atoms are minuscule objects with proportionately tiny masses. Atoms can only be observed individually using special instruments such as the scanning tunneling microscope. Over 99.9% of an atom's mass is concentrated in the nucleus, with protons and neutrons having roughly equal mass. Each element has at least one isotope with unstable nuclei that can undergo radioactive decay. This can result in a transmutation that changes the number of protons or neutrons in a nucleus. Electrons that are bound to atoms possess a set of stable energy levels, or orbitals, and can undergo transitions between them by absorbing or emitting photons that match the energy differences between the levels. The electrons determine the chemical properties of an element, and strongly influence an atom's magnetic properties.

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