"that it is played on a sandy surface. Rules do not greatly differ from those found in regular five-a-side football. A variation with increased pitch size and number of players on a team. In this variation there are five outfield players and one goalkeeper on the pitch for each team at any one time. Rules do not greatly differ from those found in five-a-side football. This is another variation with increased pitch and team size; in this case with six outfield players and a goalkeeper on each side. The rules generally do not differ from those from five-a-side. This is"
"Atom An 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). Atoms are small enough that attempting to predict their behavior using classical physics – as if they were billiard balls, for example – gives noticeably incorrect predictions due to quantum effects. Through the development of physics, atomic models have incorporated quantum principles to better explain and predict this behavior."
"u, and so a mole of carbon-12 atoms weighs exactly 0.012 kg. Atoms lack a well-defined outer boundary, so their dimensions are usually described in terms of an atomic radius. This is a measure of the distance out to which the electron cloud extends from the nucleus. However, this assumes the atom to exhibit a spherical shape, which is only obeyed for atoms in vacuum or free space. Atomic radii may be derived from the distances between two nuclei when the two atoms are joined in a chemical bond. The radius varies with the location of an atom on the"
"Atomic nucleus The atomic nucleus is the small, dense region consisting of protons and neutrons at the center of an atom, discovered in 1911 by Ernest Rutherford based on the 1909 Geiger–Marsden gold foil experiment. After the discovery of the neutron in 1932, models for a nucleus composed of protons and neutrons were quickly developed by Dmitri Ivanenko and Werner Heisenberg. An atom is composed of a positively-charged nucleus, with a cloud of negatively-charged electrons surrounding it, bound together by electrostatic force. Almost all of the mass of an atom is located in the nucleus, with a very small contribution"
"from the electron cloud. Protons and neutrons are bound together to form a nucleus by the nuclear force. The diameter of the nucleus is in the range of () for hydrogen (the diameter of a single proton) to about for the heaviest atom uranium. These dimensions are much smaller than the diameter of the atom itself (nucleus + electron cloud), by a factor of about 26,634 (uranium atomic radius is about ()) to about 60,250 (hydrogen atomic radius is about ). The branch of physics concerned with the study and understanding of the atomic nucleus, including its composition and the"
"""small nut"") inside a watery type of fruit (like a peach). In 1844, Michael Faraday used the term to refer to the ""central point of an atom"". The modern atomic meaning was proposed by Ernest Rutherford in 1912. The adoption of the term ""nucleus"" to atomic theory, however, was not immediate. In 1916, for example, Gilbert N. Lewis stated, in his famous article ""The Atom and the Molecule"", that ""the atom is composed of the ""kernel"" and an outer atom or ""shell"""" The nucleus of an atom consists of neutrons and protons, which in turn are the manifestation of more"
"configurations: The stable nucleus has approximately a constant density and therefore the nuclear radius R can be approximated by the following formula, where ""A"" = Atomic mass number (the number of protons ""Z"", plus the number of neutrons ""N"") and ""r"" = 1.25 fm = 1.25 × 10 m. In this equation, the ""constant"" ""r"" varies by 0.2 fm, depending on the nucleus in question, but this is less than 20% change from a constant. In other words, packing protons and neutrons in the nucleus gives ""approximately"" the same total size result as packing hard spheres of a constant size"
"radii of isolated neutral atoms range between 30 and 300 pm (trillionths of a meter), or between 0.3 and 3 ångströms. Therefore, the radius of an atom is more than 10,000 times the radius of its nucleus (1–10 fm), and less than 1/1000 of the wavelength of visible light (400–700 nm). For many purposes, atoms can be modeled as spheres. This is only a crude approximation, but it can provide quantitative explanations and predictions for many phenomena, such as the density of liquids and solids, the diffusion of fluids through molecular sieves, the arrangement of atoms and ions in crystals,"
"drop of water contains about 2 sextillion () atoms of oxygen, and twice the number of hydrogen atoms. A single carat diamond with a mass of contains about 10 sextillion (10) atoms of carbon. If an apple were magnified to the size of the Earth, then the atoms in the apple would be approximately the size of the original apple. Every element has one or more isotopes that have unstable nuclei that are subject to radioactive decay, causing the nucleus to emit particles or electromagnetic radiation. Radioactivity can occur when the radius of a nucleus is large compared with the"
"is mediated by gluons. The protons and neutrons, in turn, are held to each other in the nucleus by the nuclear force, which is a residuum of the strong force that has somewhat different range-properties (see the article on the nuclear force for more). The gluon is a member of the family of gauge bosons, which are elementary particles that mediate physical forces. All the bound protons and neutrons in an atom make up a tiny atomic nucleus, and are collectively called nucleons. The radius of a nucleus is approximately equal to 1.07 fm, where ""A"" is the total number"
"0.2 fm from this value. The density of the nucleus is thus: Nuclear density Nuclear density is the density of the nucleus of an atom, averaging about 2.3×10 kg/m. The descriptive term ""nuclear density"" is also applied to situations where similarly high densities occur, such as within neutron stars. The nuclear density for a typical nucleus can be approximately calculated from the size of the nucleus, which itself can be approximated based on the number of protons and neutrons in it. The radius of a typical nucleus, in terms of number of nucleons, is formula_1 where formula_2 is the mass"
"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"
"made up of positively charged protons and uncharged neutrons (together called nucleons), while the electron cloud consists of negatively charged electrons which orbit the nucleus. In a neutral atom, the negatively charged electrons balance out the positive charge of the protons. The nucleus is dense; the mass of a nucleon is approximately 1,836 times that of an electron, yet the radius of an atom is about 10,000 times that of its nucleus. The atom is also the smallest entity that can be envisaged to retain the chemical properties of the element, such as electronegativity, ionization potential, preferred oxidation state(s), coordination"
"an explosion is termed a nova. Ordinarily, atoms are mostly electron clouds by volume, with very compact nuclei at the center (proportionally, if atoms were the size of a football stadium, their nuclei would be the size of dust mites). When a stellar core collapses, the pressure causes electrons and protons to fuse by electron capture. Without electrons, which keep nuclei apart, the neutrons collapse into a dense ball (in some ways like a giant atomic nucleus), with a thin overlying layer of degenerate matter (chiefly iron unless matter of different composition is added later). The neutrons resist further compression"
"Nuclear density Nuclear density is the density of the nucleus of an atom, averaging about 2.3×10 kg/m. The descriptive term ""nuclear density"" is also applied to situations where similarly high densities occur, such as within neutron stars. The nuclear density for a typical nucleus can be approximately calculated from the size of the nucleus, which itself can be approximated based on the number of protons and neutrons in it. The radius of a typical nucleus, in terms of number of nucleons, is formula_1 where formula_2 is the mass number and formula_3 is 1.25 fm, with typical deviations of up to"
"atoms have volume, and essentially ""touch"" each other, yet at the same time exhibit strange bulk properties, consistent with a Bose–Einstein condensation. The nucleons in atomic nuclei also exhibit a wave-like nature and lack standard fluid properties, such as friction. For nuclei made of hadrons which are fermions, Bose-Einstein condensation does not occur, yet nevertheless, many nuclear properties can only be explained similarly by a combination of properties of particles with volume, in addition to the frictionless motion characteristic of the wave-like behavior of objects trapped in Erwin Schrödinger's quantum orbitals. Atomic nucleus The atomic nucleus is the small, dense"
"rapidly decreases to insignificance at distances beyond about 2.5 fm. At distances less than 0.7 fm, the nuclear force becomes repulsive. This repulsive component is responsible for the physical size of nuclei, since the nucleons can come no closer than the force allows. By comparison, the size of an atom, measured in angstroms (Å, or 1.0 × 10 m), is five orders of magnitude larger. The nuclear force is not simple, however, since it depends on the nucleon spins, has a tensor component, and may depend on the relative momentum of the nucleons. The strong nuclear force is one of"
"Atomic number The atomic number or proton number (symbol ""Z"") of a chemical element is the number of protons found in the nucleus of an atom. It is identical to the charge number of the nucleus. The atomic number uniquely identifies a chemical element. In an uncharged atom, the atomic number is also equal to the number of electrons. The sum of the atomic number ""Z"" and the number of neutrons, ""N"", gives the mass number ""A"" of an atom. Since protons and neutrons have approximately the same mass (and the mass of the electrons is negligible for many purposes)"
"physics that occurred in the first half of the 20th century, leading ultimately to the atomic bomb in 1945. In the 1911 Rutherford model, the atom consisted of a small positively charged massive nucleus surrounded by a much larger cloud of negatively charged electrons. In 1920, Rutherford suggested that the nucleus consisted of positive protons and neutrally-charged particles, suggested to be a proton and an electron bound in some way. Electrons were assumed to reside within the nucleus because it was known that beta radiation consisted of electrons emitted from the nucleus. Rutherford called these uncharged particles ""neutrons"", by the"
"Atomic mass The atomic mass (""m"") is the mass of an atom. Its unit is the unified atomic mass units (symbol: u, or Da) where 1 unified atomic mass unit is defined as of the mass of a single carbon-12 atom, at rest. For atoms, the protons and neutrons of the nucleus account for almost all of the mass, and the atomic mass measured in u has nearly the same value as the mass number. When divided by unified atomic mass units or daltons to form a pure numeric ratio, the atomic mass of an atom becomes a dimensionless value"
"its atomic weight. This would make the nuclear charge nearly equal to atomic number in smaller atoms, with some deviation from this rule for the largest atoms, such as gold. For example, Rutherford found the charge on gold to be about 100 units and thought perhaps that it might be exactly 98 (which would be close to half its atomic weight). But gold's place in the periodic table (and thus its atomic number) was known to be 79. Thus Rutherford did not make the proposal that the number of charges in the nucleus of an atom might be ""exactly"" equal"
"for a small fraction of incident particles. Rutherford realized that, because some of the alpha particles were deflected or reflected, the atom had a concentrated centre of positive charge and of relatively large mass - Rutherford later termed this positive center the ""atomic nucleus"". The alpha particles had either hit the positive centre directly or passed by it close enough to be affected by its positive charge. Since many other particles passed through the gold foil, the positive centre would have to be a relatively small size compared to the rest of the atom - meaning that the atom is"
"period). However, atomic radii tend to increase diagonally, since the number of electrons has a larger effect than the sizeable nucleus. For example, lithium (145 picometer) has a smaller atomic radius than magnesium (150 picometer). The atomic radius can be further specified as: The ionization potential is the minimum amount of energy required to remove one electron from each atom in a mole of atoms in the gaseous state. The ""first ionization energy"" is the energy required to remove the first electron, and generally the ""nth ionization energy"" is the energy required to remove the atom's ""n""th electron, after the"
"of a central charge (this is the modern atomic nucleus, though Rutherford did not use the term ""nucleus"" in his paper) surrounded by a cloud of (presumably) orbiting electrons. In this May 1911 paper, Rutherford only committed himself to a small central region of very high positive or negative charge in the atom. For concreteness, consider the passage of a high speed α particle through an atom having a positive central charge ""N"" ""e"", and surrounded by a compensating charge of ""N"" electrons. From purely energetic considerations of how far particles of known speed would be able to penetrate toward"
"approximately 0.16 nucleons per fm. If nuclei were hard-spheres, their radius would be approximately 1.1 fm, leading to a density of only 0.13 nucleons per fm, assuming ideal close-packing. Nuclear matter is dense, and the close proximity of nucleons may allow quarks in different nucleons to interact directly, leading to nucleon modification. Mean-field models predict that all nucleons experience some degree of structure modification, and they are consistent with the observation that the EMC effect increases with nuclear size, scales with local density, and saturates for very large nuclei. Furthermore, mean-field models also predict a large ""polarized EMC effect,<nowiki>""</nowiki> a"
"strong force must be present if it could deflect the massive and fast moving alpha particles. He realized that the plum pudding model could not be accurate and that the deflections of the alpha particles could only be explained if the positive and negative charges were separated from each other and that the mass of the atom was a concentrated point of positive charge. This justified the idea of a nuclear atom with a dense center of positive charge and mass. The term nucleus is from the Latin word ""nucleus"", a diminutive of ""nux"" (""nut""), meaning the kernel (i.e., the"
"""nuclide"") of the element, expressed in atomic mass units (symbol: u). In general, the mass number of a given nuclide differs in value slightly from its atomic mass, since the mass of each proton and neutron is not exactly 1 u; since the electrons contribute a lesser share to the atomic mass as neutron number exceeds proton number; and (finally) because of the nuclear binding energy. For example, the atomic mass of chlorine-35 to five significant digits is 34.969 u and that of chlorine-37 is 36.966 u. However, the atomic mass in u of each isotope is quite close to"
"number of charges) in the center, with a radius of about 1.2 × 10 meters × [atomic mass number]. Electrons were found to be even smaller. Later, scientists found the expected number of electrons (the same as the atomic number) in an atom by using X-rays. When an X-ray passes through an atom, some of it is scattered, while the rest passes through the atom. Since the X-ray loses its intensity primarily due to scattering at electrons, by noting the rate of decrease in X-ray intensity, the number of electrons contained in an atom can be accurately estimated. See also"
"many years the size of atoms has been approximated by physical models (CPK) in which the volumes of plastic balls describe where much of the electron density is to be found (often sized to van der Waals radii). That is, the surface of these models is meant to represent a specific ""level of density"" of the electron cloud, not any putative physical surface of the atom. Since the atomic radii (e.g. in Fig. 4) are only slightly less than the distance between bonded atoms, the iconic spheres intersect, and in the CPK models, this was achieved by planar truncations along"
"1967. The values are in picometres (pm). Atomic radius The atomic radius of a chemical element is a measure of the size of its atoms, usually the mean or typical distance from the center of the nucleus to the boundary of the surrounding cloud of electrons. Since the boundary is not a well-defined physical entity, there are various non-equivalent definitions of atomic radius. Three widely used definitions of atomic radius are: Van der Waals radius, ionic radius, and covalent radius. Depending on the definition, the term may apply only to isolated atoms, or also to atoms in condensed matter, covalently"
"an atomic nucleus is less than the total mass of the protons and neutrons that make it up, but this is only true after this energy from binding has been removed in the form of a gamma ray (which in this system, carries away the mass of the energy of binding). This mass decrease is also equivalent to the energy required to break up the nucleus into individual protons and neutrons (in this case, work and mass would need to be supplied). Similarly, the mass of the solar system is slightly less than the sum of the individual masses of"
"Halo nucleus In nuclear physics, an atomic nucleus is called a halo nucleus or is said to have a nuclear halo when it has a core nucleus surrounded by a ""halo"" of orbiting protons or neutrons, which makes the radius of the nucleus appreciably larger than that predicted by the liquid drop model. Halo nuclei form at the extreme edges of the table of nuclides — the neutron drip line and proton drip line — and have short half-lives, measured in milliseconds. These nuclei are studied shortly after their formation in an ion beam. Typically, an atomic nucleus is a"
"Charge radius The rms charge radius is a measure of the size of an atomic nucleus, particularly of a proton or a deuteron. It can be measured by the scattering of electrons by the nucleus and also inferred from the effects of finite nuclear size on electron energy levels as measured in atomic spectra. The problem of defining a radius for the atomic nucleus is similar to the problem of atomic radius, in that neither atoms nor their nuclei have definite boundaries. However, the nucleus can be modeled as a sphere of positive charge for the interpretation of electron scattering"