Supercomputer simulations of super-diamond suggest a path to its creation
Diamond is the strongest material known. However, another form of carbon has been predicted to be even tougher than diamond. The challenge is how to create it on Earth.
Diamond is the strongest material known. However, another form of carbon has been predicted to be even tougher than diamond. The challenge is how to create it on Earth.
Analytical Chemistry
17 hours ago
0
169
Absorption of light initiates many natural and artificial chemical processes, for example, photosynthesis in plants, human vision, or even 3D printing. Until now, it seemed impossible to control a light-driven chemical reaction ...
By design, synthetic molecules typically have specific jobs to prevent or accelerate reactions between other molecules. To help control more complicated reactions, researchers may harness spare space in one molecule to synthesize ...
Nanomaterials
Mar 15, 2024
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7
Physicists at the University of Regensburg have choreographed the shift of a quantized electronic energy level with atomic oscillations faster than a trillionth of a second.
Optics & Photonics
Mar 14, 2024
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2802
The origin of heavy elements in our universe is theorized to be the result of neutron star collisions, which produce conditions hot and dense enough for free neutrons to merge with atomic nuclei and form new elements in a ...
General Physics
Mar 13, 2024
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49
Our world may seem fragile, but Earth has been around for a very long time. If we ventured far back into the past, would we reach a time when it looked fundamentally different?
Earth Sciences
Mar 12, 2024
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89
Sometimes, seeing clearly requires complete black. For astronomy and precision optics, coating devices in black paint can cut down on stray light, enhancing images and boosting performance. For the most advanced telescopes ...
Nanophysics
Mar 12, 2024
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92
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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