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CODATA Internationally recommended values of the Fundamental Physical Constants, Atomic and Nuclear (NIST Reference on Constants, Units and Uncertainty)
Radiation, Radioactivity & Radiobiology (Martindale’s Reference Desk)
atom : the smallest particle of an element that can exist either alone or in combination — Webster
Atom is the smallest constituent unit of ordinary matter that has the properties of a chemical element. Every solid, liquid, gas, and plasma is composed of neutral or ionized atoms. Atoms are extremely small; typical sizes are around 100 picometers (a ten-billionth of a meter, in the short scale).
Every atom is composed of a nucleus and one or more electrons bound to the nucleus. The nucleus is made of one or more protons and typically a similar number of neutrons. Protons and neutrons are called nucleons. More than 99.94% of an atom’s mass is in the nucleus. The protons have a positive electric charge, the electrons have a negative electric charge, and the neutrons have no electric charge. If the number of protons and electrons are equal, that atom is electrically neutral. If an atom has more or fewer electrons than protons, then it has an overall negative or positive charge, respectively, and it is called an ion.
The electrons of an atom are attracted to the protons in an atomic nucleus by this electromagnetic force. The protons and neutrons in the nucleus are attracted to each other by a different force, the nuclear force, which is usually stronger than the electromagnetic force repelling the positively charged protons from one another. Under certain circumstances, the repelling electromagnetic force becomes stronger than the nuclear force, and nucleons can be ejected from the nucleus, leaving behind a different element: nuclear decay resulting in nuclear transmutation.
The number of protons in the nucleus defines to what chemical element the atom belongs: for example, all copper atoms contain 29 protons. The number of neutrons defines the isotope of the element. The number of electrons influences the magnetic properties of an atom. Atoms can attach to one or more other atoms by chemical bonds to form chemical compounds such as molecules. The ability of atoms to associate and dissociate is responsible for most of the physical changes observed in nature and is the subject of the discipline of chemistry. — Wikipedia
Atomic Physics is the field of physics that studies atoms as an isolated system of electrons and an atomic nucleus. It is primarily concerned with the arrangement of electrons around the nucleus and the processes by which these arrangements change.
The term atomic physics can be associated with nuclear power and nuclear weapons, due to the synonymous use of atomic and nuclear in standard English. Physicists distinguish between atomic physics — which deals with the atom as a system consisting of a nucleus and electrons — and nuclear physics, which considers atomic nuclei alone. — Wikipedia
Nuclear physics is the field of physics that studies atomic nuclei and their constituents and interactions. Other forms of nuclear matter are also studied. Nuclear physics should not be confused with atomic physics, which studies the atom as a whole, including its electrons. — Wikipedia
Phys.org - latest science and technology news stories Phys.org internet news portal provides the latest news on science including: Physics, Nanotechnology, Life Sciences, Space Science, Earth Science, Environment, Health and Medicine.
- Researchers analyze circulating currents inside...on April 30, 2021 at 2:35 pm
According to classical electromagnetism, a charged particle moving in an external magnetic field experiences a force that makes the particle's path circular. This basic law of physics are exploited in designing cyclotrons that work as particle accelerators. When nanometer-size metal particles are placed in a magnetic field, the field induces a circulating electron current inside the particle. The circulating current in turn creates an internal magnetic field that opposes the external field. […]
- Creation without contact in the collisions of...on April 29, 2021 at 2:34 pm
When heavy ions, accelerated to the speed of light, collide with each other in the depths of European or American accelerators, quark-gluon plasma is formed for fractions of a second, or even its 'cocktail' seasoned with other particles. According to scientists from the IFJ PAN, experimental data show that there are underestimated actors on the scene: photons. Their collisions lead to the emission of seemingly excess particles, the presence of which could not be explained.
- Ion beams mean a quantum leap for color-center...on April 28, 2021 at 1:16 pm
Achieving the immense promise of quantum computing requires new developments at every level, including the computing hardware itself. A Lawrence Berkeley National Laboratory (Berkeley Lab)-led international team of researchers has discovered a way to use ion beams to create long strings of "color center" qubits in diamond. Their work is detailed in the journal Applied Physics Letters.
- Physicists net neutron star gold from measurement...on April 27, 2021 at 3:00 pm
Nuclear physicists have made a new, highly accurate measurement of the thickness of the neutron "skin" that encompasses the lead nucleus in experiments conducted at the U.S. Department of Energy's Thomas Jefferson National Accelerator Facility and just published in Physical Review Letters. The result, which revealed a neutron skin thickness of .28 millionths of a nanometer, has important implications for the structure and size of neutron stars.
- 'Colloidal gels,' ubiquitous in everyday...on April 27, 2021 at 1:31 pm
Researchers at MIT have developed a new method for determining the structure and behavior of a class of widely used soft materials known as weak colloidal gels, which are found in everything from cosmetics to building materials. The study characterizes the gels over their entire evolution, as they change from mineral solutions to elastic gels and then glassy solids.