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Magnetism
Published in Daniel H. Nichols, Physics for Technology, 2019
Materials are magnetic because of the way the electrons in materials interact with one another. Atoms have nuclei made of protons and neutrons and “orbiting” the nuclei are electrons. Electrons themselves act like little magnets because of a property called spin. Two electrons with spins oriented the same way will be magnetic and spins oriented in the opposite direction will cancel each other and therefore will be nonmagnetic. Most atoms are nonmagnetic because they have an equal number of electrons with spin up and spin down in an orbit, Figure 14.2. A magnetic atom, however, does not have an equal number of electrons with spin up and spin down. Iron is an example of a magnetic material. Each magnetic atom in a bar magnet contributes to the overall magnetism of the bar.
Electronics and Emerging Paradigms
Published in Sergey Edward Lyshevski, Molecular Electronics, Circuits, and Processing Platforms, 2018
De Broglie’s postulate provides the foundation of the Schrödinger equation, which describes the behavior of microscopic particles within the microscopic structure of matter made of atoms. Atoms are composed of nuclei and electrons, and a nucleus consists of neutrons and protons. The proton is a positively charged particle, the neutron is neutral, and the electron has a negative charge. In an uncharged atom, there is an equal number of protons and electrons. Atoms may gain or lose electrons and become ions. Atoms that lose electrons become cations (positively charged) or become anions when they gain electrons (negatively charged). Considering protons, neutrons, and electrons, it should be emphasized that there exist smaller microscopic particles (quarks, antiquarks, and others) within protons and neutrons.
Chapter 6 Radioisotopes and Nuclear Medicine
Published in B H Brown, R H Smallwood, D C Barber, P V Lawford, D R Hose, Medical Physics and Biomedical Engineering, 2017
In order to understand what a radioisotope is we need to remind ourselves briefly about the structure of the atom. All atoms consist of a nucleus of protons and neutrons, with electrons in orbit around the nucleus. The difference between elements is the numbers of the fundamental particles, i.e. the protons, neutrons and electrons, which the atoms contain. Each atom consists of a nucleus surrounded by a cloud of electrons. Each nucleus is made up of a mixture of two types of nuclear particle, protons and neutrons. The conventional symbols for atoms use a superscript for the atomic mass (neutrons + protons), and a subscript for the number of protons. An example is N714, which describes an atom of nitrogen, atomic mass number 14, with seven protons. The subscript is often omitted.
Sign use and cognition in automated scientific discovery: are computers only special kinds of signs?
Published in International Journal of General Systems, 2018
Until the mid-1930s, the picture of the building blocs from which all matter was made had been clear and simple. Atoms consisted of a nucleus and electrons orbiting around it. The nucleus, in turn, was built from protons and neutrons. But with the advent of particle accelerators producing high energies and the development of cosmic rays research, the hitherto “elementary” particles began to exhibit internal structure. When in the 1950s the number of known particles exceeded 100, physicists began to look for some ordered pattern in this perplexing plethora of “elementary” particles. By 1963, particles had been grouped into so called families according to their properties (called quantum numbers). In 1964, Gell-Mann and Ne’eman found the correct representations for all known families on purely theoretical ground. They introduced into theory entirely new particles of fractional charge, called quarks. They postulated that some particles consisted of three quarks and others of a quark anti-quark pair. Now physicists believe that there are still three more quarks so that the total number of quarks equals six.
Radioactivity investigation of water and aerosols in Sharjah, United Arab Emirates
Published in Energy Sources, Part A: Recovery, Utilization, and Environmental Effects, 2019
Muhammad Zubair, Amrou Ismail, Hamad Mohammed, Sayed Azam, Ahmed Ishag
Atoms are made of a nucleus and electrons. An atom with excess energy (excited) is referred to as “Radionuclide” (Charles 2000). In order for a Radionuclide to become stable, it releases energy in the form of radiation. This process is known as “Radioactivity”. The representation of activity at time t with respect to initial activity is governed by: