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# Topic: Atomic structure

###### In the News (Mon 20 May 13)

 Atomic Structure Calculate the relative atomic mass of a substance from mass spectrometric data. The average atomic mass of chlorine is 35.5. All of the elements in the periodic table have at least 2 isotopes, the atomic mass is therefore the average of the masses of the isotopes it is made up of. www.teachmetuition.co.uk /Chemistry/Atomic_Structure/atomic1.htm   (844 words)

 Atomic Structure and the Pascal Triangle The atomic mass number of an atom, A, is given by A = Z + N, where N is the number of neutrons in the nucleus. The atomic weight of an element is the weighted average of the atomic masses of the various naturally occurring isotopes of the element, and the atomic weight scale is based on a value of exactly 12, after the carbon isotope that has an atomic mass number of 12. The greatest nuclear binding energy is found in nuclei of medium atomic number (such as Fe) where N is approximately equal to Z. For nuclei of larger atomic number, such as uranium, N is about equal to 1.5 Z, and the binding energy per nucleon is less. milan.milanovic.org /math/english/atom/atom.html   (820 words)

 Atomic Structure Overview The mass of a neutral atom is measured in atomic mass units (amu), which are based on the mass of the carbon-12 atom. In general, the atomic mass for an element given in tables is an average atomic mass that is the average of the masses of the naturally occurring isotopes of the element. A sample of an element with amass in grams numerically equal to the atomic mass is a gram atomic mass. members.aol.com /chemman41/atomic_structure_overview.htm   (2080 words)

 Bohr on Electronic Structure of Periodic Table The common character of theories of atomic constitution has been the endeavour to find configurations and motions of the electrons which would seem to offer an interpretation of the variations of the chemical properties of the elements with the atomic number as they are so clearly exhibited in the well-known periodic law. The application of the quantum theory to atomic problems-which took its starting point from the interpretation of the simple spectrum of hydrogen, for which no a priori fixation of the stationary states of the atoms was needed-has in recent years been largely extended by the development of systematic methods-for fixing the stationary states motions. On the contrary, it seems necessary to seek the configurations of the electrons in the atoms among such configurations as may be formed by the successive binding of the electrons one by one, a process the last stages of which we may assume to witness in the emission of the series spectra of the elements. dbhs.wvusd.k12.ca.us /webdocs/Chem-History/Bohr-Nature-1921.html   (1296 words)

 Structure of the Atom (grades 6-8) Protons and neutrons are responsible for most of the atomic mass e.g in a 150 person 149 lbs, 15 oz are protons and neutrons while only 1 oz. It is the number of protons that determines the atomic number, e.g., H = 1. The modern arrangement of the elements is known as the Periodic Table of Elements and is arranged according to the atomic number of elements. www.nyu.edu /pages/mathmol/textbook/atom.html   (787 words)

 Unit 2 - Atomic Structure   (Site not responding. Last check: 2007-11-06) The atomic mass of an element given in the Reference Tables for Chemistry is the weighted average mass of the naturally occurring isotopes of that element. The gram atomic mass (the mass of one mole of atoms) of an element is the mass in grams of Avogadro's number of atoms of that element as it occurs naturally. The atomic mass of a single atom (isotope) such as neon-20 is 19.992 amu while the atomic mass of the element neon (which is the weighted average of all its natural isotopes) is 20.183 amu. dwb.unl.edu /Chemistry/LearningObjectives/NY02.html   (1978 words)

 Atomic Theory I After Eugen Goldstein’s 1886 discovery that atoms had positive charges, Thomson imagined that atoms looked like pieces of raisin bread, a structure in which clumps of small, negatively charged electrons (the "raisins") were scattered inside a smear of positive charges. Atoms of different elements are distinguished from each other by their number of protons (the number of protons is constant for all atoms of a single element; the number of neutrons and electrons can vary under some circumstances). To identify this important characteristic of atoms, the term atomic number (z) is used to describe the number of protons in an atom. www.visionlearning.com /library/module_viewer.php?mid=50   (868 words)

 Atomic Structure An atom's atomic number is the number of protons there are in the nucleus. The decimal number on the periodic table is the atomic mass, the mass of one atom measured in atomic mass units(amu). So the atomic mass is the mass in amus of one atom of an element, but you rarely use the mass of one atom. library.thinkquest.org /10429/low/atomic/atomic.htm   (1186 words)

 Atomic Structure Timeline   (Site not responding. Last check: 2007-11-06) Using alpha particles as atomic bullets, probed the atoms in a piece of thin (0.00006 cm) gold foil. He wrote"The atomic number of an element is equal to the number of protons in the nucleus". Developed an explanation of atomic structure that underlies regularities of the periodic table of elements. www.watertown.k12.wi.us /HS/Staff/Buescher/atomtime.asp   (824 words)

 Atom - Wikipedia, the free encyclopedia The number of protons (and neutrons) in the atomic nucleus may also change, via nuclear fusion, nuclear fission or radioactive decay, in which case the atom is no longer the same element it was. Atoms with the same atomic number Z share a wide variety of physical properties and exhibit almost identical chemical properties (for the closest instance to an exception to this principle, see deuterium and heavy water). 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. en.wikipedia.org /wiki/Atomic   (4221 words)

 Atomic Structure Relative Atomic Mass - The average mass of the naturally occurring isotopes of the element, relative to C-12. The relative quantities of the various isotopes are calculated, and then the average mass taken, weighting the various isotopes according to their relative frequencies. The half-life of an isotope is the time taken for the number of atoms of that isotope to fall to half its original value (this is constant for any isotope). www-jcsu.jesus.cam.ac.uk /~rpc25/notes/chemistry/atomicstructure/chem1_1.html   (1317 words)

 Detailed Atomic Structure in the Aether Physics Model This atomic model is consistent within the frame work of the Aether Physics Model and is consistent with empirically observed binding energy values. As in all accepted atomic structure theories, the nucleus is composed of protons and neutrons. The structure of each of these three particles is that of a primary momentum that looks like a band with a constant spin. www.16pi2.com /detailed_atomic_structure.htm   (2981 words)

 Structure   (Site not responding. Last check: 2007-11-06) The structure of a material may be divided into four levels: atomic structure, atomic arrangement, microstructure, and macrostructure. Although the main thrust of [the materials engineer] is to understand and control the microstructure and macro-structure of various materials, [she] must first understand the atomic and crystal structures. Atomic structure influences how the atoms are bonded together, which in turn helps one to categorize materials as metals, ceramics, and polymers and permits us to draw some general conclusions concerning the mechanical properties and physical behavior of these three classes of materials. www.engr.sjsu.edu /WofMatE/Structure.htm   (1909 words)

 AS unit foundation atomic structure page N.B.: As the atomic number increases the number of protons in the nucleus increase, which increases the attraction of the electrons to the nucleus; however, this increase in positive charge is overridden by the increased distance of the negative electrons from the nucleus. At beryllium (atomic number 4) the 2s orbital is full and therefore the energy needed to remove an electron is higher than that for lithium (atomic number 3). At boron (atomic number 5) the 2p orbital has only one electron in it and this means the energy dips down a little. www.rjclarkson.demon.co.uk /found/found2.htm   (832 words)

 Lesson 3-3 Atomic Structure The number of protons in the nucleus of an atom is called its atomic number. The atomic number, which is given the symbol Z, is what determines the identity of an element. The atomic masses shown on the periodic table represent a weighted average based on the relative abundance of each isotope of a particular atom. www.fordhamprep.com /gcurran/sho/sho/lessons/lesson33.htm   (942 words)

 Atomic Structure The atomic numbers, atomic weight and atomic mass of elements in a period generally increase from left to right of the chart. Atomic number - the number of protons in the nucleus and the number of electrons in the shells. Atomic mass - the number of protons plus neutrons found in the nucleus of the atom. www.aisp.net /vster/atomstuc2.htm   (986 words)

 Atomic Structure When modern scientists began to develop atomic theory, they continued to believe the Greek idea that atoms could not be divided into anything smaller. The plum pudding theory of the structure of the atom. The atomic number of an atom is how many protons it has and hence also how many electrons it has. www.patana.ac.th /parents/curriculum/Physics_K4/units/DJFPh105.html   (1298 words)

 Atomic Structure Unit Plan ABOUT ME Three laws support the existence of atoms: the law of definite proportions, the law of conservation of mass, and the law of multiple proportions.The best explanations for these laws is that substances are made of molecules, with each molecule consisting of atoms bound together. The masses of atoms are expressed in atomic mass units (amu). The mass of an atom of the carbon-12 isotope is defined as exactly 12 atomic mass units. www.msu.edu /~giangaco/Unit_Plans/AtomicStructure.htm   (522 words)

 Modern View of Atomic Structure   (Site not responding. Last check: 2007-11-06) For convenience, the charge of atomic and sub-atomic particles are usually described as a multiple of this value (also known as the electronic charge). The units of mass used to describe atomic particles is the atomic mass unit (or amu). This is called the atomic number, and since it is always 6 for carbon, it is somewhat redundant and usually omitted. wine1.sb.fsu.edu /chm1045/notes/Atoms/AtomStr2/Atoms03.htm   (813 words)

 Atomic Structure This law states that "the properties of the elements are periodic functions of atomic number." The periodic table is a chart which categorizes elements by "groups" and "periods." All elements are ordered by their atomic number. Atomic mass is measured in Atomic Mass Units where 1amu = (1/12)mass of carbon measured in grams. Atomic orbitals are known as s, p, d, and f orbitals. www.shodor.org /unchem/basic/atom   (1742 words)

 (Q-2)   The Atomic Structure of Matter Viewing the atoms of a gas as colliding spheres, in particular, explained very well the theory of heat and the classical gas laws--even the uneven distribution of molecular (or atomic) velocities in a hot gas (calculated by Maxwell, his "Maxwellian distribution") and sophisticated ideas like the second law of thermodynamics. In later years, in electric discharges in rarefied gases, physicists managed to separate tiny negatively charged electrons, as well as positive ions, the atomic or molecular fragments left behind when electrons were detached. Of all the atomic spectra, the simplest is that of hydrogen--not surprising, since hydrogen is the smallest of atoms, and presumably the simplest. www-istp.gsfc.nasa.gov /stargaze/Q2.htm   (1331 words)

 Atomic Structure   (Site not responding. Last check: 2007-11-06) Atomic Theories Timeline of the Evolution of the Atomic Model: March 11, 2002. Structure of the Atom (grades 6-8) The modern arrangement of the elements is known as the Periodic Table …; more info Periodic Table of Elements: Vanadium - V … Atomic structure, chemical and physical properties, and table of nuclides. www.atomicstructure.info   (358 words)

 Hydrogen energies and spectrum The basic hydrogen energy level structure is in agreement with the Bohr model. Common pictures are those of a shell structure with each main shell associated with a value of the principal quantum number n. If the radial probabilities for the states are used to make sure you understand the distributions of the probability, then the Bohr picture can be superimposed on that as a kind of conceptual skeleton. hyperphysics.phy-astr.gsu.edu /hbase/hyde.html   (396 words)

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