Engineering
A new kind of solar panel, developed at the University of Michigan, has achieved 9% efficiency in converting water into hydrogen and oxygen—mimicking a crucial step in natural photosynthesis. Outdoors, it represents a major ...
Jan 4, 2023
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326
Electronics & Semiconductors
Over the past decades, engineers have created increasingly advanced and highly performing integrated circuits (ICs). The rising performance of these circuits in turn increased the speed and efficiency of the technology we ...
Robotics
If you want to build a fully functional nanosized robot, you need to incorporate a host of capabilities, from complicated electronic circuits and photovoltaics to sensors and antennas.
Mar 17, 2021
1
344
Robotics
Vector-borne diseases are illnesses that can be transmitted to humans by blood-feeding insects, such as mosquitoes, ticks and fleas. Mosquitoes are known to contribute to the spread of a number of vector-borne diseases, including ...
Engineering
MIT researchers have, for the first time, fabricated a diamond-based quantum sensor on a silicon chip. The advance could pave the way toward low-cost, scalable hardware for quantum computing, sensing, and communication.
Sep 25, 2019
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943
Energy & Green Tech
After years of making progress on an organic aqueous flow battery, Harvard University researchers ran into a problem: the organic anthraquinone molecules that powered their ground-breaking battery were slowly decomposing ...
May 29, 2019
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111
Computer Sciences
Computer scientists at University of California, Davis, Maynooth University in Ireland and the California Institute of Technology have created DNA molecules that can self-assemble into patterns essentially by running their ...
Mar 20, 2019
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1728
Engineering
Scientists have invented a new clock that keeps time more precisely than any that have come before.
Dec 1, 2018
1
271
Engineering
Researchers commonly study brain function by monitoring two types of electromagnetism—electric fields and light. However, most methods for measuring these phenomena in the brain are very invasive.
Oct 22, 2018
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133
Hardware
MIT researchers have developed the first molecular clock on a chip, which uses the constant, measurable rotation of molecules—when exposed to a certain frequency of electromagnetic radiation—to keep time. The chip could ...
Jul 16, 2018
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289
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.
This text uses material from Wikipedia, licensed under CC BY-SA
