Australian scientists have discovered an enzyme that converts air into energy. The finding, published today in the journal Nature, reveals that this enzyme uses the low amounts of the hydrogen in the atmosphere to create ...
Biochemistry
Mar 8, 2023
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41992
A University of Portsmouth physicist has explored whether a new law of physics could support the much-debated theory that we are simply characters in an advanced virtual world.
General Physics
Oct 9, 2023
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3489
For years, if you asked the people working to create new pharmaceutical drugs what they wished for, at the top of their lists would be a way to easily replace a carbon atom with a nitrogen atom in a molecule.
Analytical Chemistry
Nov 1, 2023
1
1419
It could be raining diamonds on planets throughout the universe, scientists suggested Friday, after using common plastic to recreate the strange precipitation believed to form deep inside Uranus and Neptune.
Materials Science
Sep 4, 2022
0
153
Physicists at EPFL, within a large European collaboration, have revised one of the fundamental laws that has been foundational to plasma and fusion research for over three decades, even governing the design of megaprojects ...
Condensed Matter
May 17, 2022
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3174
A team of scientists from Ohio University, Argonne National Laboratory, the University of Illinois-Chicago, and others, led by Ohio University Professor of Physics, and Argonne National Laboratory scientist, Saw Wai Hla, ...
General Physics
May 31, 2023
2
7011
Scientists have advanced in discovering how to use ripples in space-time known as gravitational waves to peer back to the beginning of everything we know. The researchers say they can better understand the state of the cosmos ...
General Physics
Jan 20, 2023
51
5296
Researchers led by Chang Liu of PPPL have unveiled a promising approach to mitigating damaging runaway electrons created by disruptions in tokamak fusion devices. Key to the approach was harnessing a unique type of plasma ...
Plasma Physics
Sep 28, 2023
0
580
Scientists are increasingly studying quantum entanglement, which occurs when two or more systems are created or interact in such a manner that the quantum states of some cannot be described independently of the quantum states ...
Optics & Photonics
Jan 3, 2023
0
545
On September 12, 1962, then US president John F Kennedy informed the public of his plan to put a man on the Moon by the end of the decade.
Space Exploration
Sep 10, 2022
23
143
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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