Atom

This model was created to account for chemical phenomena such as bonding, rather than physical phenomena such as atomic spectra. Dictionary definitions from Wiktionary
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News stories from Wikinews. The cubes could share edges or faces to form chemical bonds. Bears, usually anthropomorphized, appear frequently as characters in popular culture; see List of fictional bears. Lewis in 1916, had cubical atoms with electrons statically held at the corners. A bear also features prominently in the legend of Saint Romedius, who is also said to have tamed one of these animals and had the same bear carry him from his hermitage in the mountains to the city of Trento. Another model of historical interest, proposed by Gilbert N. In the arms of the bishopric of Freising (illustration, right) the bear is the dangerous totem animal tamed by Saint Corbinian and made to carry his civilized baggage over the mountains: the allegory of the civilizing influence of Christianity is inescapable.

Further refinements of quantum theory such as the Dirac equation and quantum field theory made smaller impacts on the theory of atoms. Bears are a common symbol of heraldry. Even today, these theories are used in the Hartree-Fock quantum chemical method to determine the energy levels of atoms. The bear is also the name-emblem of Berlin. Together with Wolfgang Pauli's exclusion principle, this allowed study of atoms with great precision when digital computers became available. Numerous cities around the world have adopted the bear as a symbol, notably the Swiss capital Bern, which takes its name from the German for bear, bär. In 1925, Erwin Schroedinger developed a full theory of quantum mechanics, described by the Schroedinger equation. The theory of the bear taboo is taught to almost all beginning students of Indo-European and historical linguistics; the putative original PIE word for bear is itself descriptive, because a cognate word in Sanskrit is rakshas, meaning "harm, injury" [1].

However, the model was unable to explain multielectron atoms, predict transition rates or describe fine and hyperfine structure. In the Finnish countryside, the word for "bear" remains taboo to this day. The ad hoc Bohr-Sommerfeld model was extremely difficult to use, but it made impressive predictions in agreement with certain spectral properties. Thus four separate Indo-European language groups do not share the same PIE root. Bohr's model was extended by Arnold Sommerfeld in 1916 to include elliptical orbits, using a quantization of generalized momentum. Arthur), Sanskrit *ṛkṣa, Hittite hartagga) seems to have been subject to taboo deformation or replacement (as was the word for wolf, wlk^wos), resulting in the use of numerous unrelated words with meanings like "brown one" (English bruin) and "honey-eater" (Slavic medved). They were not allowed to spiral into the nucleus, because they could not lose energy in a continuous manner; they could only make quantum leaps between fixed energy levels. In addition, the Proto-Indo-European word for bear, *hr̥ktos (ancestral to the Greek arktos, Latin ursus, Welsh arth (c.f.

In 1913, Niels Bohr used this idea in his Bohr model of the atom, in which the electrons could only orbit the nucleus in particular circular orbits with fixed angular momentum and energy. There has been evidence about early bear worship in China and among the Ainu culture as well. Quantum theory revolutionized physics at the beginning of the 20^th century when Max Planck and Albert Einstein postulated that light energy is emitted or absorbed in fixed amounts known as quanta. This is why the bear was a greatly respected animal, with several euphemistic names. Secondly, the model did not explain why excited atoms emit light only in certain discrete spectra. The prehistoric Finns, along with most finno-ugric peoples, considered the bear as the spirit of one's forefathers. Firstly, a moving electric charge emits electromagnetic waves; according to classical electromagnetism, an orbiting charge would steadily lose energy and spiral towards the nucleus, colliding with it in a tiny fraction of a second. Anthropologists such as Joseph Campbell have regarded this as a common feature in most of the fishing and hunting-tribes.

The planetary model of the atom still had shortcomings. There is some evidence for prehistoric bear worship, see Arctic, Arcturus, Great Bear, Berserker, Kalevala. The nucleus was later discovered to contain protons, and further experimentation by Rutherford found that the nuclear mass of most atoms surpassed that of the protons it possessed; this led him to postulate the existence of neutrons, whose existence would be proven in 1932 by James Chadwick. The discovery has shown that while all other Brown Bears share a Brown Bear as their closest relative, those of Alaska's ABC Islands differ and share their closest relation with the Polar Bear. This led to the planetary model of the atom in which pointlike electrons orbited in the space around a massive compact nucleus like planets orbiting the Sun. The researchers discovered that their DNA was unique compared to Brown Bears anywhere else in the world. About 1 in 8000 of the alpha particles, however, were heavily deflected (by more than 90 degrees). Researchers Gerald Shields and Sandra Talbot of the University of Alaska Fairbanks Institute of Arctic Biology studied the DNA of several samples of the species and found that their DNA is different from that of other Brown Bears.

Rutherford observed that most of the particles passed straight through the sheet with little deflection (striking a fluorescent screen on the other side). There is also evidence that, unlike their neighbors elsewhere, the Brown Bears of Alaska's ABC Islands are more closely related to Polar Bears than they are to other Brown Bears in the world. In the gold foil experiment, alpha particles (emitted by polonium) were shot through a sheet of gold. The many similarities between the two pandas are thought to represent convergent evolution for feeding primarily on bamboo. However, an experiment conducted in 1909 by colleagues of Ernest Rutherford demonstrated that atoms have a most of their mass and positive charge concentrated in a nucleus. Others place it with the racoons in Procyonidae or in its own family, the Ailuridae. At first, it was believed that the electrons were distributed more or less uniformly in a sea of positive charge (the plum pudding model). The status of the Red Panda remains uncertain, but many experts, including Wilson and Reeder, classify it as a member of the bear family.

Physicists later invented a new term for such indivisible units, "elementary particles", since the word atom had come into its common modern use. Although there has previously been much discussion as to whether the Giant Panda belongs to the bear family or the raccoon family, recent DNA analyses have shown that the Giant Panda is a member of the Family Ursidae and as such is more closely related to other bears. Since cathode rays are emitted from matter, this proved that atoms are made up of subatomic particles and are therefore divisible, and not the indivisible atomos postulated by Democritus. Extinct bear genera include Arctodus, Agriarctos, Agriotherium, Plionarctos and Indarctos. Thomson published his work proving that cathode rays are made of negatively charged particles (electrons). This genus radiated in Asia and ultimately gave rise to the first true bears (genus Ursus) in Europe, 5 million years ago. However, in 1897, J.J. Cephalogale gave rise to a lineage of early bears, the genus Ursavus.

For much of this time, atoms were thought to be the smallest possible division of matter. The origins of the bears can be traced back to the raccoon-sized, dog-like Cephalogale from the middle Oligocene and early Miocene (approximately 20-30 million years ago) of Europe. This theory was validated experimentally in 1911 by French physicist Jean Perrin. Although bears are often described as having evolved from a dog-like ancestor, their closest living relatives are the pinnipeds (walruses, seals, and sea lions). In 1905, Albert Einstein theorised that this Brownian motion was caused by the water molecules continuously knocking the grains about, and developed a mathematical theory around it. Other members of the Caniformia include wolves and other dog-like mammals (family Canidae), weasels, skunks, and badgers (family Mustelidae), raccoons (family Procyonidae), and walruses (family Odobenidae), seals (family Phocidae), and sea lions (family Otariidae). In 1827, biologist Robert Brown observed that pollen grains floating in water constantly jiggled about for no apparent reason. Bears are members of the order Carnivora, suborder Caniformia, and family Ursidae.

Atomic theory conflicted with the theory of infinite divisibility, which states that matter can always be divided into smaller parts. A number of hybrids have been bred between American Black, Brown and Polar Bears (see Ursinae hybrids). 4NO + 2O₂ → 4NO₂. The Asiatic Black Bear and the Polar Bear used to be placed in their own genera, Selenarctos and Thalarctos. 4NO + O₂ → 2N₂O₃. The genera Melursus and Helarctos are included in the genus Ursus. In one combination, these gases formed dinitrogen trioxide (N₂O₃), but when he repeated the combination with double the amount of oxygen (a ratio of 1:2), they instead formed nitrogen dioxide (NO₂). Sun Bears are the smallest, only a bit smaller than the average person.

The experiment in question involved combining nitrous oxide (NO) with oxygen (O₂). Kodiak Bears are the largest type of bear (Polar Bears are the heaviest though), indeed one of the largest extant carnivores. He deduced this after the experimental discovery of the law of multiple proportions — that is, if two elements form more than one compound between them, then the ratios of the masses of the second element which combine with a fixed mass of the first element will be ratios of small whole numbers. The Brown Bear is Finland's national animal. In 1808, John Dalton proposed that an element is composed of atoms of a single, unique type, and that although their shape and structure was immutable, atoms of different elements could combine to form more complex structures (chemical compounds). Bears have an average life expectancy of 25–40 years. None of these ideas, however, were founded in scientific experimentation. Bears in captivity used to be trained to dance, box, or unicycle, but it is now controversial to use animals in this way.

Sometime between the 5th century BC and 1st century CE, Buddhist and Jaina philosophers in ancient India also began developing atomic theories (see Indian atomism). Laws have been passed in many areas of the world to protect bears from hunters or habitat destruction. For instance, the atoms of a liquid were thought to be smooth, allowing them to slide over each other. Higher body heat and being easily roused may be adaptations because female bears bear cubs during this winter sleep. (See atomism for more details.) The Greeks believed that atoms were all made of the same material but had different shapes and sizes, which determined the physical properties of the material. Recycling urine is quite a physiological feat. Democritus and Leucippus, Greek philosophers in the 5th century BC, presented the first theory of atoms. They do not wake normally during 'hibernation' therefore do not eat, drink, urinate or defecate the entire period.

The seeding of the interstellar medium by heavy elements eventually allowed the formation of terrestrial planets like the Earth. The body temperature of bears, on the other hand, drops only a few degrees from normal and heart rate slows slightly. These stars fused heavier elements through stellar nucleosynthesis during their lives and through supernova nucleosynthesis as they died. In true hibernators, body temperatures drop to near ambient and heart rate slows drastically, but they periodically rouse themselves to urinate or defecate and eat from stored food. After Big Bang nucleosynthesis, no heavier elements could be created until the formation of the first stars. While many bear species do go into a physiological state called hibernation or winter sleep, it is not true hibernation. These photons are still detectable today in the cosmic microwave background. Many bears of northern regions are assumed to hibernate in the winter.

This allows most of the photons in the universe to travel unimpeded for billions of years. Normally, bears are very solitary and will not remain close together for long periods of time. Once atoms become neutral, they only absorb photons of a discrete absorption spectrum. The cubs reach sexual maturity at seven years. This process is called recombination, during which the first neutral atoms took form. However, they will still remain nearby for three years. It was then cool enough to allow the nuclei to capture electrons. Then, they are weaned.

Big Bang chronology of the atom continues to approximately 379,000 years after the Big Bang when the cosmic temperature had dropped to just 3,000 K. They will be fed by milk at first and will start hunting with the mother in three months. However, although nuclei (fully-ionized atoms) were created, neutral atoms themselves could not form in the intense heat. The cubs, usually born in litters of 1–3, will stay with the mother for six months. Hydrogen makes up approximately 75% of the atoms in the universe; helium makes up 24%; and all other elements make up just 1%. Cubs come out toothless, blind, and bald. During this process, nuclei of hydrogen and helium formed abundantly, but almost no elements heavier than lithium. Bears reproduce seasonally, usually after a period of inactivity similar to hibernation.

In models of the Big Bang, Big Bang nucleosynthesis predicts that within one to three minutes of the Big Bang almost all atomic material in the universe was created. The bear's courtship period is very brief. This was produced at CERN in the ATHENA and ATRAP experiments using the Antiproton Decelerator. The only exceptions are polar bears and large adult brown bears, whose heavy weight makes it difficult to climb trees. Since antimatter is very difficult to produce and store, only a small amount antihydrogen has ever existed on Earth. Most bears are able to climb trees to chase prey or gain access to additional vegetation. Antimatter can also form atoms, composed of positrons, antiprotons, and antineutrons. They use their excellent memories to return to locations where food was plentiful in past years or seasons.

When electrons deep inside large atoms are knocked out (for example by beta radiation), replacement atoms fall deep into the electric potential of the nucleus, producing high-energy x-rays. Bears travel over large territories in search of food, remembering the details of the landscape they cover. For example, the hyperfine transitions (including the important 21 cm line) produce low-energy radio waves. Male young usually leave their mothers to live in other areas, but females often live in an area that overlaps that of their mother. Not all parts of the atomic spectrum are in visible light part of the electromagnetic spectrum. A male and female may live in an overlapping home range, each defending their range from other bears of the same sex. Due to the distinctive spectral lines that each element produces, they are able to tell the chemical composition of distant planets, stars and nebulae. Other bears may live alone but exist in a social network.

In spectroscopic analysis, scientists can use a spectrometer to study the atoms in stars and other distant objects. Giant pandas may also form small social groups, based on recent evidence, perhaps because bamboo is more concentrated than the patchy food resources of other bear species. The resulting pattern of gaps is called the absorption spectrum. Alaskan brown bears group in the same area to feed on salmon during the annual salmon runs, when the fish swim upriver to reach their spawning grounds. If a set of atoms is illuminated by a continuous spectrum, it will only absorb specific wavelengths (energies) of photon that correspond to the differences in its energy levels. Bears form temporary groups only when food is plentiful in a small area. When these atoms fall back toward the ground state, they will produce an emission spectrum. Bears mostly live alone, except for mothers and their cubs, or males and females during mating season.

If a set of atoms is heated (such as in an arc lamp), their electrons will move into excited states. They will, however, defend their cubs ferociously. Since each element has a unique set of energy levels, each creates its own light pattern unique to itself: its own spectral signature. For the most part, bears are shy and are easily frightened of humans. An electron in a higher-energy orbital may drop to a lower-energy orbital by emitting a photon. Some of the large species, such as the polar bear and the grizzly bear, are dangerous to humans, especially in areas where they have become used to people. An electron may move from a lower-energy orbital to a higher-energy orbital by absorbing a photon with energy equal to the difference between the energies of the two levels. Hunting times are usually in the dusk or the dawn except when humans are nearby.

Normally, an atom is found in its lowest-energy ground state; states with higher energy are called excited states. Bears will commonly travel far for food. Since each element in the periodic table consists of an atom in a unique configuration with different numbers of protons and electrons, each element can also be uniquely described by the energies of its atomic orbitals and the number of electrons within them. They can also go to a river or other body of water to capture fish. Many other types of bonds exist, including:. They eat lichens, roots, nuts, and berries. The formation of a bond causes a strong attraction between two atoms, creating molecules or ionic compounds. They are mainly omnivorous, although some have a more specialised diet, such as polar bears.

This can be achieved one of two ways: an atom can either share electrons with other atoms (a covalent bond), or it can remove electrons from (or donate electrons to) other atoms (an ionic bond). Bears live in a variety of habitats from the tropics to the Arctic and from forests to snowfields. Atoms may fill their valence shells by chemical bonding. Bears living in the wild tend to die younger than their zoo-counterparts. Fluorine is the most reactive of all elements. A bear's life span seems to last about 25 to 40 years. Also, atoms that need only few electrons (such as the halogens) to fill their valence shells are reactive. Large male polar bears may weigh twice as much as females, while smaller male and female bears are much more similar in weight.

Alkali metals are therefore very reactive, with caesium, rubidium, and francium being the most reactive of all metals. In all bear species, males are larger than females, but the difference between sexes varies and is greatest in the largest species. Conversely, atoms with few electrons in their valence shell are more reactive it is. Several species, such as the sun bear and spectacled bear have a light-colored chest with facial markings. This means that atoms with full valence shells (the noble gases) are very unreactive. For example, American black bears may be black, brown, reddish-brown, or bluish-black. Every atom is most stable with a full valence shell. Colors of a bear's fur can also vary within species.

Alkali metals contain one electron on their outer shell; alkaline earth metals, two electrons; halogens, seven electrons; and various others. Fur color varies among species, ranging from white, blonde or cream, to black, and white to all black or all brown. Therefore, elements with the same number of valence electrons are grouped together in the columns of the periodic table of the elements. A bear's fur is long and shaggy. The number of electrons in an atom's outermost shell (the valence shell) governs its bonding behavior. They are also stronger than most carnivores and their limbs are more flexible and agile. Atoms that have either lost or gained electrons are called atomic ions (with either positive(+) or negative charge(−), respectively). Although slower than most carnivores, a running bear can reach speeds of up to 50 km/h (30 mph).

These ultra-heavy elements are generally highly unstable and decay quickly. They walk with their weight on the soles of their hindfeet, with the heel touching the ground, while the toes of the forefeet are used more for balance. Elements not normally found in nature have been artificially created by nuclear bombardment; as of 2006, elements have been created through atomic number 116 (given the temporary name ununhexium). While most carnivores tend to walk on their toes in a way that is adapted for speed, bears have a plantigrade stance. Several elements that do not occur on Earth have been found to be present in stars. These claws can be used to climb trees, rip open termite nests and beehives, dig up roots, or catch prey, depending on the species. Most of the elements lighter than uranium (Z=92) have stable-enough isotopes to occur naturally on Earth (with the notable exception of technetium Z=43). Each paw has five long, sharp claws that are unretractible, unlike cats.

Virtually all elements heavier than hydrogen and helium were created through stellar nucleosynthesis and supernova nucleosynthesis. Bears have four limbs that end in paws. The elements with atomic number 84 (polonium) and heavier have no stable isotopes and are all radioactive. Bears' molar teeth are broad, flat and are used to shred and grind plant food into small digestable pieces. Almost all isotopes of each element are radioactive; only a few are stable. Normal canine teeth in a carnivore are generally large and pointed used for killing prey, while bears' canine teeth are relatively small and typically used in defense or as tools. Tritium is an unstable isotope which decays through a process called radioactivity. Bear teeth are not specialized for killing their prey like those of cats.

The hydrogen isotope which also contains one neutron so is called deuterium or hydrogen-2; the hydrogen isotope with two neutrons is called tritium or hydrogen-3. Depending on the species, bears can have 32 to 42 teeth. The simplest atom is the hydrogen isotope protium, which has atomic number 1 and atomic mass number 1; it consists of one proton and one electron. Black bears, and likely other bears, have color vision to help them identify fruits and nuts. The atomic mass listed for each element in the periodic table is an average of the isotope masses found in nature, weighted by their abundance. A bear's eyesight is probably similar in acuity (sharpness) to the human eye. For example, carbon-14 contains 6 protons and 8 neutrons in each atom, for a total mass number of 14. Their claws are used for ripping, digging, and catching.

When writing the name of an isotope, the element name is followed by the mass number. Their teeth are used for defense and tools and depend on the diet of the bear. These are called the isotopes of an element. They have broad paws, long snouts, and round ears. Each has the same atomic number but a different mass number. They are capable of standing up on their hind legs. Each element can have numerous kinds of atoms with the same number of protons and electrons but varying numbers of neutrons. Bears have a large body with powerful limbs.

The number of neutrons A−Z in an atom has no effect on which element it is. Common characteristics of bears include a short tail, excellent senses of smell and hearing, five un-retractable claws, and long, dense, shaggy fur. The atomic mass A, atomic mass number, or nucleon number of an element is the total number of protons and neutrons in an atom of that element, so-called because each proton and neutron has a mass of about 1 amu. . The elements may be sorted according to the periodic table in order of increasing atomic number. The adjective, ursine, is used to describe things of bearlike nature. All atoms with the same atomic number share a wide variety of physical properties and exhibit the same chemical properties. A bear is a large mammal of the order Carnivora, family Ursidae.

For example, carbon atoms are atoms containing six protons. The Bear by William Faulkner. The atomic number determines which chemical element the atom is. Bears of the World, Terry Domico, Photographs by Terry Domico and Mark Newman, Facts on File, Inc, 1988, hardcover, ISBN 0816015368. Atoms are generally classified by their atomic number Z, which corresponds to the number of protons in the atom. The harder you try, the better the bear you are!. At room temperature, atoms making up gases in the air move at a speed of 500 m/s (about 1100 mph or 1800 km/h). To try like a bear means to try your hardest to catch the attention of a certain lady.

As the temperature of the system is increased, the kinetic energy of the particles in the system is increased, and their speed of motion increases. Stephen Colbert frequently attacks bears as "godless killing machines" mobilized against humanity on The Colbert Report. The temperature of a collection of atoms is a measure of the average energy of motion of those atoms; at 0 kelvin (absolute zero) atoms would have no motion. Microsoft Bear is an unofficial mascot hidden in Windows 3.1 and Windows 95. This contracts the size of the electron shells, so that more electrons fit in the only a slightly greater volume. In homosexual slang, the term "Bear" refers to male individuals who possess physical attributes much like a bear, such as a heavy build, abundant body hair, and commonly facial hair. The reason for this is that heavy elements have large positive charge on their nuclei, which strongly attract the electrons to the center of the atom. In CB slang, "bear" (or "smokey", in reference to Smokey Bear) is a nickname for highway patrol.

Their sizes are roughly the same to within a factor of 2. The bear is a common national symbol for Russia (and the Soviet Union), as used in the Ronald Reagan political ad "Bear in the woods.". Atoms of different elements do vary in size, but the sizes do not scale linearly with the mass of the atom. The constellations Ursa Major and Ursa Minor represent bears. Nearly all the mass of an atom is in its nucleus, yet almost all the space in an atom is filled by its electrons. for sports teams; and a bear cub was mascot of the 1980 Summer Olympics. If an atom were the size of a stadium, the nucleus would be the size of a marble. The bear, the bruin, or specific types of bears are popular nicknames or mascots, e.g.

So the ratio of the size of the hydrogen atom to its nucleus is about 100,000:1. Indeed the farming of bears in China has led to a huge increase in consumption of bear bile since the 1980's with many people prepared to pay very high prices for the 'superior' bile of a wild bear. Compare this to the size of the proton (the only particle in the nucleus of the hydrogen atom), which is approximately 10⁻¹⁵ m. There is no evidence to suggest that farming bears has reduced pressures on wild bear populations. As an example, the size of a hydrogen atom is estimated to be approximately 1.0586×10⁻¹⁰ m (twice the Bohr radius). They are kept in appalling conditions and usually have bile drained from their gall bladders using catheters inserted into their abdomen or with hypodermic needles. For any atom, one might use the radius at which the electrons of the valence shell are most likely to be found. Thousands of bears are farmed for their bile in China, Vietnam and Korea.

For atoms that can form solid crystal lattices, the distance between the centers of adjacent atoms can be easily determined by x-ray diffraction, giving an estimate of the atoms' size. This has had a major impact on populations of bears around the world. Since the electron cloud does not have a sharp cutoff, the size of an atom is not easily defined. The peoples of China, Japan and Korea use bears' body parts and secretions (notably their gall bladders and bile) as part of traditional Chinese medicine. These include: electron microscopes (such as in scanning tunneling microscopy (STM)), atomic force microscopy (AFM), nuclear magnetic resonance (NMR) and x-ray microscopy. Many cultures regard bears as possessing healing powers. However, there are ways of detecting the positions of atoms on the surface of a solid or a thin film so as to obtain images. Its opposite is a bull market, and bullish sentiment from bulls.

Atoms are much smaller than the wavelengths of light that human vision can detect, so atoms cannot be seen in any kind of optical microscope. Pessimistic forecasting or negative activity is said to be bearish (due to the stereotypical posture of bears looking downwards), and one who expresses bearish sentiment is a bear. In nuclear fission, a single large nucleus is divided into two or more smaller nuclei. In the stock market, a bear market is a period of declining prices. In nuclear fusion, two light nuclei come together and merge into a single heavier nucleus. That bear became the prototype for the Teddy bear, which is a stuffed animal toy. Nuclear transformations also take place in nuclear reactions. president Theodore "Teddy" Roosevelt refused to shoot in Mississippi.

When an excited nucleus emits a photon to return to the ground state, the photon has very high energy and is called a gamma ray. Some bears have been famous in their own right, like the bear that U.S. However, these transitions typically require thousands of times more energy than electron excitations. Subspecies Borneo Sun Bear (Helarctos (Ursus) malayanus euryspilus). In addition, like the electrons of the atom, the nucleons of nuclei may be pushed into excited states of higher energy. Sun Bear, Helarctos malayanus