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 the 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 broken down further using chemical methods. During the late nineteenth century and early twentieth century, physicists have managed to find the structure and subatomic components inside the atom, to prove that the 'atom' is not never be divided again.The principles of quantum mechanics used by physicists then successfully model the atom. In the day-to-day observations, the relative atomic considered a very small objects with proportionately tiny masses anyway. Atoms can only be monitored using special equipment such as atomic force microscopy. More than 99.9% of the mass of the atom is concentrated in the nucleus, [note 1] with protons and neutrons are nearly the same mass. Each element has at least one isotope with unstable nuclei that can undergo radioactive decay. This can result in transmutation, which changes the number of protons and neutrons in the nucleus. Electrons are bound to the atom contains a number of energy cedar, or orbital, which is stable and can undergo transitions between these cedar to absorb or emit photons corresponding to the difference between the energy levels. The electrons in the atom determines the chemical properties of an element, and affects the magnetic properties of the atom.The components of the atom1. Subatomic ParticlesThough the word atom originally meant a particle that can not be cut again into smaller particles, in modern scientific terminology, 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 +.Of all these subatomic particles, electrons are the lightest, with a mass of 9.11 × 10-31 electron kg and has a negative charge. Size of the electron is very small in such a way there is no measurement techniques that can be used to measure its size. Protons have a positive charge and a mass 1836 times heavier than the electron (1.6726 × 10-27 kg). Neutrons are not electrically charged and massless free or 1839 times the mass of the electron (1.6929 × 10-27 kg).In the standard model of physics, both protons and neutrons are composed of elementary particles called quarks. Quark belongs to the fermion group of particles and is one of the two basic building blocks of matter (the other is the lepton). There are six types of quarks and each quark has a fractional charge of electricity of +2 / 3 or -1 / 3. Proton consists of two up quarks and one down quark, when the neutron consists of one up quark and two down quarks. This difference affects the composition of the quark mass and charge differences between the two particles. Quarks bound together by the strong nuclear force mediated by gluons. Gluon is a member of the standards which are intermediaries boson forces of physics2. The nucleusnti atom consists of protons and neutrons bound together in the center of the atom. Collectively, protons and neutrons are called nucleons (particles making up the core). Nucleus diameter ranging between 10-15 and 10-14m. Estimated core radii equal to 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 force of attraction of potential called the residual strong force. At distances smaller than 2.5 fm, the force is stronger than the electrostatic force that causes protons repel each other.Atoms of the same chemical 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 nuclides, while the number of neutrons relative to the number of protons determines the stability of the nucleus, with certain isotopes of elements will carry radioactive decay.Neutrons and protons are two different types of fermions. Pauli exclusion principle prohibits the existence of identical fermions (such as multiple protons) occupying the same quantum physical state at the same time. Therefore, every proton in the nucleus of an atom should occupy different quantum states with energy cedar respectively. Pauli principle is also valid for the neutron. This prohibition does not apply to a proton and neutron occupying the same quantum state.For atoms with low atomic number, atomic nuclei that have more than the number of protons neutrons potentially falls into a lower energy state through a radioactive decay that causes the number of protons and neutrons balanced. Therefore, the atom with the number of protons and neutrons are more stable balanced and less likely to decay. However, with increasing atomic number, repulsion between protons makes the nucleus requires a higher proportion of neutrons to maintain the stability again. At the core of the most severe, the ratio of neutrons per proton required to maintain the stability will increase to 1.5.Overview of the process that produces nuclear fusion of deuterium nuclei (consisting of one proton and one neutron). A positron (e +) is emitted along with an electron neutrino.The number of protons and neutrons in the atomic nucleus can be modified, although this requires a very high energy due to the attraction of strong force. Nuclear fusion occurs when many particles of atoms combine to form a heavier nucleus. For example, at the core of the Sun protons require about 3-10 keV energy to overcome the repulsion between each other and merge into a single core. [41] Nuclear Fission is the opposite of the fusion process. In nuclear fission, the nucleus split into two smaller nuclei. This usually occurs through radioactive decay. The nucleus can also be modified through the shooting of high-energy subatomic particles. If this change the number of protons in the nucleus of an atom is changed elements.If the mass of the nucleus following a fusion reaction is less than the number of initial particle mass constituent, then the difference is caused by the release of radiant energy (such as gamma rays), as found in mass-energy equivalence formula of Einstein, E = mc2, where m is the mass of the lost and c is the speed of light. This deficit is part of the binding energy of the new nucleus.Fusion of two nuclei that produce larger nuclei with lower atomic numbers than iron and nickel (the total number of nucleons equal to 60) is usually exothermic, which means that this process releases energy. Is the process of energy release that makes nuclear fusion in stars can be maintained. For heavier nuclei, the binding energy per nucleon in the nucleus begins to decline. This means that the fusion process will be endothermic3. Electron cloudElectrons in an atom are drawn by the protons in the nucleus via the electromagnetic force. This force binds the electrons inside an electrostatic potential well around the core. This means that the external energy needed for an electron to escape from the atom. The closer an electron in the nucleus, the greater the attraction force, so that the electrons that are close to the center of the potential well require more energy to escape.Electrons, like other particles, have properties such as particle and as a wave (wave-particle duality). Electron cloud is a region inside the potential well where each electron produces a kind of silent waves (ie waves that do not move relative to the nucleus) in three dimensions. This behavior is determined by atomic orbitals, which is a mathematical function that calculates the probability of an electron will appear at a particular location when its position is measured. There will be only one particular set of orbitals that are around the nucleus, as another wave patterns will rapidly decay into a more stable form.Each atomic orbital corresponds to a particular electron energy cedars. Electrons can change the situation onto a higher energy by absorbing a photon. Besides being able to ride to the cedar higher energy, an electron can also go down to a lower energy state by emitting the excess energy as photons.The energy required to remove or add an electron (electron binding energies) is smaller than the binding energy of nucleons. For example, only 13.6 eV is required to remove an electron from the hydrogen atom. Compare this with the energy of 2.3 MeV are needed to break the deuterium nucleus. [49] Atoms are electrically neutral because the number of protons and electrons of the same. Atoms that lack or excess of electrons known as ions. Electrons are located outside of the core can be shared or transferred to other nearby atoms. In this way, the atoms can bond together to form molecules
The propertiesMassSince the majority of the mass of an atom comes from protons and neutrons, the total number of particles in an atom is called the mass number. The mass of the 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 atom neutral, which is about the size of 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 approximately equal to the mass number times the atomic mass unit. The heaviest stable atom is lead-208, [52] with a mass of 207.9766521 u.The chemists usually use the unit for the stated number of moles of atoms. A mole is defined as the number of atoms contained in exactly 12 grams of carbon-12. This number is approximately 6.022 × 1023, which is also known as the Avogadro constant. Thus an element with an atomic mass of 1 u will have a mass of one mole of atoms 0.001 kg. For example, Carbon has an atomic mass of 12 u, so one mole of carbon atoms has a mass of 0.012 kgSizeAtom does not have a clear outer boundary, so that the dimensions of atoms 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, bond types 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 group numbers (right to left).Therefore, the smallest atom is helium with a radius of 32 pm, when the largest is cesium at 225 pm radius. This dimension is thousands of times smaller than the wavelengths of light (400-700 nm), so that the atoms can not be seen using ordinary optical microscope. However, atoms can be monitored using atomic force microscopy.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 atoms of carbon. [Note 2] If an apple is enlarged to the size of the amount of the Earth, then the atoms in the apple would look at the size of apples beginning tersebu
Tidak ada komentar:
Posting Komentar