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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.
- Limits of atomic nuclei predicted: Scientists...on January 13, 2021 at 5:53 pm
Novel calculations have enabled the study of nearly 700 isotopes between helium and iron, showing which nuclei can exist and which cannot. In an article published in Physical Review Letters, scientists from TU Darmstadt, the University of Washington, the Canadian laboratory TRIUMF, and the University of Mainz report how they simulated for the first time using innovative theoretical methods a large region of the chart of nuclides based on the theory of the strong interaction.
- New cathode material for high-performing sodium...on January 13, 2021 at 2:04 pm
ANSTO contributed to a large international collaboration on advanced sodium ion batteries led by French researchers, which provides a direction for the design of high-performing sodium ion electrodes. Advanced sodium ion batteries could be used for large scale energy storage.
- Galaxy mergers could limit star formationon January 11, 2021 at 4:00 pm
Astronomers have looked nine billion years into the past to find evidence that galaxy mergers in the early universe could shut down star formation and affect galaxy growth.
- Nuclear fusion group calls for building a pilot...on January 6, 2021 at 9:00 pm
The main criticism about nuclear fusion has been that its vast potential as a commercial source of energy has always been just out of reach.
- The map of nuclear deformation takes the form of...on December 30, 2020 at 3:30 pm
Until recently, scientists believed that only very massive nuclei could have excited zero-spin states of increased stability with a significantly deformed shape. Meanwhile, an international team of researchers from Romania, France, Italy, the USA and Poland showed in their latest article that such states also exist in much lighter nickel nuclei. Positive verification of the theoretical model used in these experiments allows describing the properties of nuclei unavailable in Earth laboratories.