Atom is a basic unit of matter, which consists of the atomic nucleus and the negatively charged electron cloud surrounding it. Atomic nucleus consists of positively charged protons and electrically neutral neutrons (except in the atomic nucleus Hydrogen-1, which has no neutrons). Electrons in an atom bound to the atomic nucleus by the electromagnetic force. As well as a collection of atoms can be bonded to each other, and form a molecule. Atom containing the number of protons and electrons are equal is neutral, while the number of protons and electrons are different positive or negative and is referred to as ion. Atoms are grouped based on the number of protons and neutrons contained in the nucleus. The number of protons in an atom determines the chemical element the atom, and the number of neutrons determines the isotope of the element.
The term comes from the Greek atom (ἄτομος / ATOMOS, α-τεμνω), which means it can not be cut or something that can not be divided again. The concept of the atom as a component that can not be divided again was first proposed by philosophers of India and Greece. In the 17th century and into the 18th, the chemists laid the foundations of this idea by showing that certain substances can not be divided further using chemical methods. During the late 19th century and early 20th century, the physicists managed to find the structure and subatomic components inside the atom, proving that the 'atom' is not can not be divided again. The principles of quantum mechanics used by physicists then successfully model the atom.
In everyday observation, relatively atom is considered a very small objects that have mass proportionally small anyway. Atoms can only be monitored with the use of special equipment such as an atomic force microscope. More than 99.9% of the mass of the atom is concentrated in the nucleus, with protons and neutrons are almost the same mass. Each element has at least one isotope with an unstable nucleus, which can undergo radioactive decay. This can result in transmutation, which change the number of protons and neutrons in the nucleus. Bound electrons in an atom contains a number of energy levels, or orbitals, which is stable and can undergo transitions between those levels by absorbing or emitting photons corresponding to the energy difference between levels. The electrons in an atom determines the chemical properties of an element, and affects the magnetic properties of the atom.
History.
The concept that matter is composed of separate units that can not be subdivided into smaller units has existed for millennia. However, these ideas were founded in abstract and philosophical, rather than based on empirical observations and experiments. Philosophically, the description of the properties of atoms varies depending on the culture and the philosophy flow, and often had spiritual elements in it. Nevertheless, the basic idea of the atom can be accepted by scientists thousands of years later, because he could elegantly explain new discoveries in the field of chemistry.
The referral to the concept of the atom can be traced back to ancient India in the year 800 BC, which is described in the text of philosophy as such and paramanu Jainism. Stream schools Nyaya and Vaisesika developed a theory that explains how atoms combine to form objects more complex. A century later appeared references to the atoms in the Western world by Leucippus, who later by his pupil Democritus that view systematized. Approximately 450 BCE, Democritus coined the term ATOMOS (Greek: ἄτομος), which means "can not cut" or "can not be divided again". Democritus theory of atoms is not an attempt to describe a physical phenomenon in detail, but rather a philosophy that tries to provide answers to the changes that occur in nature. Philosophy is also common in India, however, modern science decided to use the term "atomic" coined by Democritus.
Further progress in the understanding of the atom begins with the development of chemistry. In 1661, Robert Boyle published The Sceptical Chymist who argued that the materials in the world is composed of various combinations of "corpuscules", ie different atoms. This is in contrast with the classical view that argues that the material is composed of elements of air, earth, fire, and water. In 1789, the term element (element) is defined by a nobleman and a French researcher, Antoine Lavoisier, as a base material that can not be divided further by using chemical methods.
Various atoms and molecules described in the book of John Dalton, A New System of Chemical Philosophy (1808).
In 1803, John Dalton used the concept of atoms to explain why elements always react in comparison round and fixed, and why certain gases is more soluble in water than other gases. He proposed that each element contains a unique single atoms, and the atoms can then be joined to form chemical compounds.
Particle theory was later confirmed further in 1827, when botaniwan Robert Brown uses a microscope to observe the dust floating on the water and found that the dust is moving randomly. This phenomenon became known as "Brownian motion". In 1877, J. Desaulx propose that this phenomenon is caused by the thermal motion of water molecules, and in 1905 Albert Einstein made a mathematical analysis against this motion. French physicist Jean Perrin then use Einstein's work to determine the mass and atomic dimensions in experiments, which is then bound to be verification of Dalton's atomic theory.
Based on the results of his research on cathode rays, in 1897, JJ Thomson discovered the electron and the properties of subatomic. This undermines the concept of the atom as a unit that can not be divided again. Thomson believed that the electrons are distributed evenly throughout the atom, and charge-balanced by the presence ocean cargo positive charge (the plum pudding model).
But in 1909, researchers under the direction of Ernest Rutherford fired helium ions into thin sheets of gold, and found that a small fraction of the ions reflected by the reflection angle sharper than what is predicted by the theory of Thomson. Rutherford then proposed that the positive charge of an atom and most of its mass is concentrated in the nucleus, with electrons orbiting an atomic nucleus like planets around the sun. Positively charged helium ions that pass through this dense core must be reflected by the reflection angle sharper. In 1913, when experimenting with the results of the process of radioactive decay, Frederick Soddy discovered that there is more than one kind of atom at each position on the periodic table. The term isotope was coined by Margaret Todd as a suitable name for different atoms, but is the same element. J.J. Thomson subsequently discovered a technique for separating atom types through his work on ionized gas.
Bohr model of the hydrogen atom shows the electron jump between orbits of fixed and emits a photon energy with a certain frequency.
Meanwhile, in 1913 the physicist Niels Bohr's atomic model Rutherford reviewing and proposed that electrons located on the quantized orbits and can jump from one orbit to another orbit, nevertheless can not freely rotating spiral into and out in a state of transition. An electron must absorb or emit a certain amount of energy to be able to make the transition between the orbits of this fixed. If the light of the material is heated radiating through the prism, it produces a multicolored spectrum. The appearance of certain spectral lines is successfully explained by these orbital transitions theory.
The chemical bond between atoms and then in 1916 by Gilbert Newton Lewis described as the interaction between the electrons of the atom. Over their regularity properties of chemicals in the period table of chemical, American chemist Irving Langmuir in 1919 argued that this could be explained if the electrons in an atom interconnected or gathered in the particular forms. A group of electrons is expected to occupy a set of petals electrons around the nucleus.
Stern-Gerlach experiment in 1922 provide further evidence of the quantum properties of atoms. When a beam of silver atoms were fired through a magnetic field, the file is separated in accordance with the direction of the atomic angular momentum (spin). Therefore, the direction of spin is random, this file is expected to spread into one line. But in fact the file is divided into two parts, depending on whether the atomic spin oriented upwards or downwards.
In 1926, using the idea that Louis de Broglie particles behave like waves, Erwin Schrödinger developed a mathematical model of the atom that describes a three-dimensional electrons as waves rather than as points of particles. The consequences of using waveforms to explain this is that the electron is not possible to mathematically calculate the position and momentum of a particle simultaneously. This became known as the uncertainty principle, formulated by Werner Heisenberg in 1926. According to this concept, for each measurement position, one can only obtain a range of probable values for momentum, and vice versa. Although this model is hard to visualize, it may well explain the properties of atoms previously observed can not be explained by any theory. Therefore, a model that describes the atomic electrons orbit the atomic nucleus like planets around the sun aborted and replaced by a model of the atomic orbitals around the nucleus where electrons are most likely.
Developments in mass spectrometry permitted a precise measurement of the atomic mass. This spectrometer equipment using magnets to deflect the trajectory of the ion beam, and the amount of deflection is determined by the ratio of the atomic mass of the payload. Chemist Francis William Aston used this equipment to show that isotopes have different masses. The mass difference between isotopes is an integer, and he referred to as the rules of integers. Explanation of the isotope mass difference is solved after the discovery of the neutron, an electrically neutral particle with a mass similar to the proton, ie by James Chadwick in 1932. Isotopes later described as an element with the same number of protons but a different number of neutrons in atomic nucleus.
In the 1950s, the development of particle accelerators and particle detectors allowed scientists to study the impacts of atoms moving at high energies. Neutrons and protons then known as hadrons, namely composite tiny particles called quarks. Standard models of nuclear physics and then developed to explain the properties of atomic nuclei in terms of the interaction of these subatomic particles.
Around 1985, Steven Chu and colleagues at Bell Labs developed a technique to reduce the temperature of the atoms using lasers. In the same year, a group of scientists headed by William D. Phillips managed to trap the sodium atoms in a magnetic trap. Claude Cohen-Tannoudji then combine these two techniques to cool a small number of atoms up to several microkelvins. This allows scientists to study atoms with very high precision, which in turn brings scientists find Bose-Einstein condensation.
Historically, a single atom is very small to be used in scientific applications. But recently, a variety of devices using a single metal atom connected by organic ligands (single electron transistor) has been made. Various studies have been conducted to trap and slow the rate of cooling of atoms using lasers to gain a better understanding of the properties of atoms.
The components of the atom.
Subatomic particles.
Although initially the word atom means a particle that can not be cut again into smaller particles, in the terminology of modern science, the atom is composed of various subatomic particles. Subatomic particles are electrons, protons, and neutrons. However, hydrogen-1 has no neutrons. Similarly, the positive hydrogen ions H +.
From all these subatomic particles, electrons are the lightest, the electron mass of 9.11 × 10-31 kg and has a negative charge. Electron size is very small so universally no measurement techniques that can be used to measure its size. Protons have a positive charge and a mass 1,836 times heavier than electrons (1.6726 × 10-27 kg). Neutrons have no electrical charge and mass of 1,839 times the mass of the free electron or (1.6929 × 10-27 kg). In the standard model of physics, both protons and neutrons are composed of elementary particles called quarks. The quark belongs to the class of fermionic particles and is one of the two basic constituents of matter (the others are leptons). There are six types of quarks and each of these quarks have fractional electric charge of +2/3 or -1/3. Proton consists of two quarks up and one down quark, when neutrons are composed of quarks one up and two down quarks. This distinction affects the difference in mass and charge between the two particles. Quarks bound together by the strong nuclear force mediated by gluons. Gluon is a member of the gauge bosons which are intermediate forces of physics.
Atomic nucleus.
Binding energy needed by the nucleon to escape from the core to the various isotopes.
Atomic nucleus consists of protons and neutrons are bound together at the center of the atom. Collectively, protons and neutrons are referred to as nucleons (core constituent particles). The diameter of the nuclei ranged from 10-15 up to 10-14m. The radius of the nucleus is approximately equal to \ begin {smallmatrix} 1.07 \ sqrt opq2wl 3g [{A} \ end {smallmatrix} fm, where A is the number of nucleons. It is very small compared with the radius of the atom. Nucleons are bound together by the attractive force potential called the residual strong force. At distances smaller than 2.5 fm, this style is more powerful than the electrostatic force that causes the protons repel each other.
Atoms of the same element have the same number of protons, called the atomic number. An element can have varying numbers of neutrons. These variations are called isotopes. The number of protons and neutrons of an atom determines the atomic nuclide, while the number of neutrons relative to the number of protons determines the stability of the atomic nucleus, with certain isotopes will run radioactive decay.
Neutrons and protons are two different types of fermions. Pauli exclusion principle forbids the existence of identical fermions (such as multiple protons) occupy a same quantum physical state at the same time. Therefore, each proton in the nucleus should occupy different quantum states with energy levels respectively. The Pauli principle also applies to neutrons. This prohibition does not apply to protons and neutrons occupy the same quantum state.
For atoms with low atomic number, atomic nuclei that have more than the number of protons neutrons potentially fall into a lower energy state through a radioactive decay that causes the number of protons and neutrons balanced. Therefore, the atom the number of protons and neutrons are more stable balanced and tend not to decay. However, with increasing atomic number, repulsion between protons create neutrons atomic nuclei require a higher proportion again to maintain stability. At the core of most weight, the ratio of neutrons per proton is needed to maintain stability will increase to 1.5.
Overview of nuclear fusion process that produces a deuterium nucleus (consisting of one proton and one neutron). A positron (e +) in conjunction with electron neutrinos emitted.
The number of protons and neutrons in the atomic nucleus can be changed, although this requires a very high energy because of the attraction force is strong. Nuclear fusion occurs when many atomic particles combine to form a heavier nucleus. For example, at the core of the Sun, protons require approximately 3-10 keV energy to overcome the repulsion between each other and merge into a single core.
Nuclear fission is the opposite of the fusion process. In nuclear fission, the core was split into two smaller nuclei. This usually occurs through radioactive decay. Atomic nucleus can also be modified through shooting high-energy subatomic particles. If this change the number of protons in the nucleus, the atom will change the element.
If the mass of the nucleus after the fusion reaction is smaller than the sum of the mass of the initial particle constituent, then the difference is caused by the release of radiant energy (such as gamma rays), as found in the formula of Einstein's mass-energy equivalence, E = mc2, where m is the mass of the lost and c is the speed of light. This deficit is part of the new core binding energy.
The fusion of two nuclei that produce larger nuclei with lower atomic numbers than iron and nickel (total number of nucleons equal to 60) is usually exothermic, which means that this process releases energy. Is the energy release process that makes nuclear fusion in stars can be maintained. For heavier nuclei, the binding energy per nucleon in the nucleus begins to decrease. This means that the fusion process will be endothermic.
Electron cloud.
Potential well which shows the minimum energy V (x) which is required to achieve each position x. A particle with energy E is limited to the range of positions between x1 and x2.
The electrons in an atom is pulled by protons in the nucleus through the electromagnetic force. This force binds the electrons in the electrostatic potential well around the core. This means that the external energy is required so that the electrons can escape from the atom. The closer an electron in the nucleus, the greater the force of its attractions, so that the electrons are located close to the center of the potential well require greater energy to escape.
Electrons, like other particles, have properties such as particle or as a wave (wave-particle duality). Electron cloud is a region in the potential well where each electron produce a kind of stationary waves (ie waves that do not move relative to the core) three-dimensional. This behavior is determined by atomic orbitals, which is a mathematical function that calculates the probability that an electron will appear at a particular location when its position is measured.
There will be only one set of specific orbital located around the nucleus, because the other wave patterns will rapidly decays into a more stable form.
The first wave function five atomic orbitals. Three 2p orbitals shows one node field.
Each atomic orbital corresponds to a particular electron energy levels. Electrons can change the situation to a higher energy level by absorbing a photon. Besides being able to ascend to a higher energy level, an electron can also be down to a lower energy state by emitting excess energy as photons.
The energy required to remove or add one electron (electron binding energy) is smaller than the binding energy of nucleons. For example, only 13.6 eV required to detach electrons from hydrogen atoms. Compare with an energy of 2.3 MeV are required to break a deuterium nucleus. Atoms are electrically neutral because the number of protons and electrons are equal. Atoms deficiency or excess of electrons called ions. Electrons are located at the outside of the core can be transferred or shared to other nearby atoms. In this way, the atoms can bond together to form molecules.
The properties.
Nuclear properties.
By definition, the two atoms with an identical number of protons in its nucleus belong to the same chemical element. Atoms with the same number of protons but with different numbers of neutrons are two different isotopes of the same element. For example, all hydrogen has one proton, but there is an isotope of hydrogen that has no neutrons (hydrogen-1), an isotope which has one neutron (deuterium), two neutrons (tritium), etc. Hydrogen-1 is the form of the most common isotope of hydrogen. Sometimes he called protium. All isotopes of elements atomic number greater than 82 are radioactive.
From about 339 nuclides are formed naturally on Earth, 269 of which have never been observed to decay. In the chemical elements, 80 of the elements that are known to have one or more stable isotopes. Elements 43, 63, and all elements higher than 83 do not have a stable isotope. Twenty-seven elements have only one stable isotope, when the number of stable isotopes of the most widely observed in the element tin with 10 stable isotopes.
Mass.
Because the majority of the mass of the atom is derived from protons and neutrons, the total number of particles in an atom is called the mass number. The mass of an atom at rest is often expressed using atomic mass units (u) which is also called the dalton (Da). This unit is defined as one-twelfth the mass of carbon-12 atoms neutral, which is approximately 1.66 × 10-27 kg. Hydrogen-1 which is the lightest isotope of hydrogen has an atomic weight of 1.007825 u. Atom has a mass that is approximately equal to its mass multiplied by the number of atomic mass units. Heaviest stable atom is lead-208, with a mass of 207.9766521 u.
The chemists usually use the unit for the stated number of moles of atoms. One mole is defined as the number of atoms contained in exactly 12 grams of carbon-12. This amount is approximately 6.022 × 1023, which is also known by the name of the Avogadro constant. Thus an element with an atomic mass of 1 u will have a mass of one mole of atoms of 0.001 kg. For example, Carbon has an atomic mass of 12 u, so that one mole of carbon atom has a mass of 0.012 kg.
Size.
Atoms do not have a clear outer limits, so that the dimensions of the atom is usually described as the distance between the two nuclei when the two atoms joined together in a chemical bond. The radius varies depending on the type of atom, the type of bond that is involved, the number of atoms in the vicinity, and the atomic spin. In the periodic table of elements, atomic radius will tend to increase with increasing period (top to bottom). Instead atomic radius will tend to increase with decreasing number of groups (right to left). Therefore, the smallest atom is helium with a radius of 32 pm, when the largest is cesium with radius 225 pm.
These dimensions thousands of times smaller than light waves (400-700 nm), so that the atoms can not be seen using ordinary optical microscope. However, the atoms can be monitored using an atomic force microscope.
Atomic size is very small, so small width of a strand of hair can hold about 1 million carbon atoms. One drop of water also contains about 2 × 1021 atoms of oxygen. One carat diamond with a mass of 2 × 10-4 kg contains about 1022 carbon atoms. If an apple is enlarged to the size of the size of the Earth, the atoms in the apple will look at the size of the initial apple.
Radioactive decay.
This diagram shows the half-life (T½) multiple isotopes with proton number Z and the number of protons N (in seconds).
Each element has one or more unstable isotopes core will undergo radioactive decay, causing the core to release particles or electromagnetic radiation. Radioactivity can occur when the radius of the nucleus is very large compared to the radius of the strong force (only works at a distance of about 1 fm).
Forms of radioactive decay is the most common:
Alpha decay, occurs when a nucleus emits alpha particles (helium nucleus consisting of two protons and two neutrons). The result of this decay is a new element with atomic number smaller.
Beta decay is governed by the weak force, and is produced by the transformation of a neutron into a proton, or a proton into a neutron. Transformation of a neutron into a proton will be followed by the emission of an electron and an antineutrino, when the transformation of a proton into a neutron followed by the emission of a positron and a neutrino. Emission electron or positron emissions are called beta particles. Beta decay can increase or decrease the number of atoms of a single core.
Gamma decay, produced by changes in the core energy level to a lower state, causing the emission of electromagnetic radiation. This can happen after the emission of an alpha or beta particles from radioactive decay.
Types of radioactive decay of other, less commonly include the release of neutrons and protons from the nucleus, the emission of more than one beta particle, or decay which resulted in the production of high-speed electrons that are not beta rays, and the production of high-energy photons that are not gamma rays
Each radioactive isotope has a characteristic decay time period (half-life) which is the length of time required by half the amount of sample to decay exhausted. The process of decay is exponential, so after two half-lives, the remaining 25% will only isotope.
Magnetic moment.
Each elementary particles have intrinsic properties of quantum mechanics known as spin. Analogous to the spin angular momentum of an object rotating on its center of mass, although not rigid particles behave like this. Spin is measured in units of reduced Planck constant (ħ), with electrons, protons, and neutrons all have spin ½ ħ, or "spin-½". In an atom, electrons move around the nucleus of an atom in addition to having a spin also have orbital angular momentum, when the nuclei have also angular momentum because of its own nuclear spin.
The magnetic field generated by an atom (called the magnetic moment) is determined by a combination of various kinds of this angular momentum. However, it remains the largest contribution comes from the spin. Therefore, the electrons obey the Pauli exclusion principle, ie no two electrons can be found in the same quantum state, the electron pairs that are bound to each other have opposite spins, with one spin ride, and the other one spin down. Both opposite spins this will neutralize each other, so that the total magnetic dipole moment becomes zero at some electrons even numbered atoms.
On the odd electron atoms like iron, the existence of unpaired electrons cause the atoms to be ferromagnetic. Atomic orbitals of the atoms around the overlap and decrease energy state is achieved when the spin of unpaired electrons arranged one lined. This process is referred to as the exchange interaction. When the magnetic moments of ferromagnetic atoms arranged in rows, materials composed of atoms can produce macroscopic field which can be detected. The materials are paramagnetic atoms with magnetic moments are arranged randomly, so there is no magnetic field is generated. However, the magnetic moment of each individual atom will be arranged in a row when given magnetic field.
Atomic nucleus can also have spin. Usually the core spins aligned in random directions because of thermal equilibrium. However, for certain elements (such as xenon-129), it is possible to polarize the nuclear spin state significantly so that the spins are aligned in the same direction. Condition called hyperpolarization. This phenomenon has important applications in magnetic resonance imaging.
Aras-energy level.
When an electron bound to an atom, it has potential energy is inversely proportional to the distance of the electron to the nucleus. It is measured by the amount of energy required to remove electrons from atoms and are usually expressed with units electronvolts (eV). In the model of quantum mechanics, electrons can occupy bound only one set of circumstances that is centered on the core, and each state corresponds to a specific energy level. The lowest energy state of a bound electron is called the ground state, when the higher energy state called excited states.
In order for an electron to jump from one state to another, it must absorb or emit photons at energies corresponding to the potential energy difference between the two levels. Energy emitted photon is proportional to its frequency. Each element has a characteristic spectrum of each. It relies on nuclear charge, subshells are filled with electrons, the electromagnetic interactions between electrons, and other factors.
When a continuous energy spectrum emitted by a gas or plasma, some photons are absorbed by atoms, causing electrons to change their energy level. Excited electron will spontaneously emit this energy as a photon and falls back to a lower energy level. Therefore, the atoms behave like a filter that will form a series of absorption bands. Spectroscopic measurements of the strength and width of the spectrum allows the determination of the composition and physical properties of a substance.
Closely monitoring the spectral lines showed that some showed a smooth separation. This happens because the spin-orbit coupling is an interaction between the spin with the motion of the outer electrons. When an atom is in an external magnetic field, spectral lines separated into three or more components. It is called the Zeeman effect. Zeeman effect is caused by the interaction of the magnetic field with the magnetic moments of atoms and electrons.
Some atoms can have many configurations of electrons with the same energy level, so it will appear as a line spectrum. Interaction with the magnetic field shifts the atomic electron configurations towards a slightly different energy levels, resulting in multiple spectral lines. The existence of an external electric field can cause splitting and shift of spectral lines by changing the electron energy levels. This phenomenon is referred to as the Stark effect.
Valence and bonding behavior.
Petals or outermost electron shell of an atom in a state that is not combined referred to as the electrons in the valence shell and the petals are called valence electrons. The number of valence electrons determine the behavior of the atoms bond with other atoms. Atoms tend to react with each other through the charging (or discharging) the outer valence electrons of atoms. Chemical bonds can be seen as a transfer of electrons from one atom to another, as observed in the sodium chloride and other ionic salts. However, there are many elements that show multiple valence behavior, or the tendency to divide the electrons with different amounts on different compounds. Thus, the chemical bond between these elements tend to be sharing electrons rather than electron transfer. Examples include the element carbon in organic compounds.
Chemical elements are often shown in the periodic table that displays the chemical properties of an element are patterned. The elements with the same number of valence electrons are grouped into particles (called groups). Elements on the outer petals rightmost table is fully charged, causing these elements tend inert (noble gases).
Circumstances.
Picture of the formation of a Bose-Einstein condensate.
A number of atoms found in a state of matter that varies depending on the physical conditions, ie temperature and pressure. By changing these conditions, the material can change into a solid, liquid, gas, and plasma. In each of these circumstances can also have various phases of matter. For example, the solid carbon, it can be either graphite or diamond.
At temperatures close to absolute zero, the atoms can form a Bose-Einstein condensate, in which quantum mechanical effects are usually only observed at the atomic scale observed macroscopically. Set passed chill atoms behave like a super atom.
Identification.
Scanning tunneling microscope image showing the individual atoms on a gold surface (100).
Scanning tunneling microscope (scanning tunneling microscope) is a microscope that is used to look at the surface of an object at the atomic level. This tool uses quantum tunneling phenomena which allow particles to penetrate the barrier that usually can not be bypassed.
An atom can be ionized by removing one electron. Existing cargo causes a curved trajectory atom when it passes through a magnetic field. The radius of the ion trajectory is determined by atomic mass. The mass spectrometer uses this principle to calculate the mass-to-charge ratio of ions. If a sample contains multiple isotopes, the mass spectrometer can determine the proportion of each isotope by measuring the intensity of the ion beam is different. Techniques to vaporize atoms include atomic emission spectroscopy inductively coupled plasma (inductively coupled plasma atomic emission spectroscopy) and inductively coupled plasma mass spectrometry (inductively coupled plasma mass spectrometry), both using a plasma to vaporize the sample analysis.
The other method is more selective release of energy electron spectroscopy (electron energy loss spectroscopy), which measures the energy loss of the electron beam in a transmission electron microscope when it interacts with the sample. Atom-probe tomograph has sub-nanometer resolution in 3-D and can chemically identify individual atoms using time-of-mass spectrometry.
The spectrum of excited states can be used to analyze the atomic composition of distant stars. Specific wavelengths of light emitted by the star can be separated and matched to the quantized transitions in free gas atoms. Color star can then be replicated using a gas discharge lamp containing the same element. Helium in the Sun found using this method 23 years before he was discovered on Earth.
The origin and current conditions.
Atoms occupy about 4% of the total energy density in the observable universe, with an average density of about 0.25 atoms / m3. In the Milky Way, the atom has a higher concentration, the density of matter in the interstellar medium ranged from 105 up to 109 atoms / m3. The sun itself is believed to be in the Local Bubble, which is an area that contains a lot of gas ions, so that the density around it is about 103 atoms / m3. Star forming dense clouds in the interstellar medium and star evolutionary process will lead to an increase in the content of elements heavier than hydrogen and helium in the interstellar medium. Up to 95% atom is concentrated in the Milky Way stars, and the total mass of atoms forms about 10% of the mass of the galaxy. Rest mass is dark matter that is not clearly known.
Nucleosynthesis.
Stable protons and electrons appeared one second after the Big Bang. During the following three minutes, Big Bang nucleosynthesis produced most of the helium, lithium and deuterium, and perhaps also some beryllium and boron. The first atom (with electrons bound to him) theoretically created 380,000 years after the Big Bang, when the universe expands cool enough to allow the electrons bound to the nucleus. Since then, the nuclei begin to join the stars through the process of nuclear fusion and generate more elements up to iron.
Such as lithium-6 isotope produced in space by cosmic ray spallation. This occurs when a high-energy proton strikes an atomic nucleus, causing a large number of nucleons to be ejected. Elements heavier than iron were produced in supernovae through the r-process and in AGB stars through the s-process. Both involve the capture of neutrons by nuclei. Elements such as lead formed largely through the radioactive decay of other elements heavier.
Earth.
Most atoms that make up the Earth and includes all beings life ever been in its present form in the nebula of molecular clouds collapse and form the Solar System. The rest is the result of radioactive decay and proportion can be used to determine the age of the Earth through radiometric dating. Most helium in the Earth's crust is a product of alpha decay.
There is a bit of atoms in the Earth early in its formation does not exist and is also not a result of radioactive decay. Carbon-14 continuously generated by cosmic rays in the atmosphere. Some of the atoms in the Earth artificially produced by reactors or nuclear weapons. Of all the transuranium elements atomic number greater than 92, only plutonium and neptunium alone contained in the Earth naturally. Transuranium elements has a radioactive half-life shorter than the age of the Earth, so that these elements have long decayed. The exception contained in the possibility of plutonium-244 stored in the cosmic dust. Plutonium and neptunium natural ingredient produced from neutron capture in uranium ore.
Earth contains approximately 1.33 × 1050 atoms. In the atmosphere of the planet, there are a small number of atoms of noble gases such as argon and neon. Remaining 99% of the atoms in the Earth's atmosphere in the form of bound molecules, such as carbon dioxide, diatomic oxygen, and nitrogen diatomic. At the Earth's surface, the atoms bond together to form a wide variety of compounds, including water, salts, silicates and oxides. Atoms can also combine to form materials that are not made up of molecules, crystals and metals for example solid or liquid.
The theoretical shape and form rare.
3-Dimensional Imaging existence of "island of stability" in the far right
When isotopes with atomic numbers higher than lead (62) are radioactive, there is an "island of stability" posed for some elements with atomic numbers above 103. The super-heavy elements are likely to have a relatively stable core of the radioactive decay . Stable superheavy atoms is most likely is Unbihexium, with 126 protons 184 neutrons.
Each particle of matter has a corresponding antimatter particles with opposite electrical charge. Thus, the positron is antielectron positively charged protons and antiprotons are negatively charged, when matter and antimatter meet, they annihilate each other.
There is an imbalance between the number of particles of matter and antimatter. This imbalance is still not completely understood, although there is a theory that gives Baryogenesis possible explanation. Antimatter is never found naturally. However, in 1996, antihydrogen successfully synthesized at the CERN laboratory in Geneva.
There are also other rare atoms are made to replace the protons, neutrons, or electrons with other particles are charged the same. For example, an electron can be replaced with a heavier muon, muon atomic form. These types of atoms can be used to test the predictions of physics.
Thank you for reading this article. Written and posted by Bambang Sunarno.
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DatePublished: January 14, 2015 at 11:36
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