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Topic: Atomic number


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  Chem4Kids.com: Glossary: A
The atomic mass is the total mass of one atom of an element.
Atomic mass is not measured in pounds or grams, scientists used something called Daltons.
The atomic number is the number of an element on the periodic table.
www.chem4kids.com /glossary   (957 words)

  
  Method of imaging the atomic number of a sample - Patent 4571491
Atomic number imaging by a computerized axial tomographic scanner (hereinafter referred to as "CAT") is based on the fact that X-ray attenuation depends both on the density and the chemical composition of a material.
A plurality of calibration materials which have a plurality of different known atomic numbers and densities are scanned with a CAT at a first energy to determine the attenuation coefficients for the plurality of calibration materials at the first energy.
For a mixture containing several elements, the effective atomic number Z* is defined as: ##EQU1## where f.sub.i is the fraction of electrons on the i.sup.th element of atomic number Z.sub.i, relative to the total number of electrons in the mixture, that is, ##EQU2## where n.sub.i is the number of moles of element i.
www.freepatentsonline.com /4571491.html   (4226 words)

  
  Atomic Structure   (Site not responding. Last check: )
The number associated with a mole is Avogadro's number.
The decimal number on the periodic table is the atomic mass, the mass of one atom measured in atomic mass units(amu).
This number in grams is the mass of 1 mole of that element.
library.thinkquest.org /10429/low/atomic/atomic.htm   (1186 words)

  
  Atomic number - Wikipedia, the free encyclopedia
In chemistry and physics, the atomic number (Z) is the number of protons found in the nucleus of an atom.
It was later shown that the atomic number corresponds to the electric charge of the nucleus — in other words the number of protons.
The atomic number is closely related to the mass number (although they should not be confused) which is the number of protons and neutrons in the nucleus of an atom.
en.wikipedia.org /wiki/Atomic_number   (304 words)

  
 Glossary [A-Bomb to AWACS] | atomicarchive.com
The atomic number of an element, which indicates its place in the periodic table of elements, is the number of protons (positively charged particles) in the nucleus of one of its atoms.
Atomic number is often symbolized with the letter Z and is shown as a numerical subscript to the left of its chemical symbol.
For example, the letter C preceded by a superscript number 12 and a subscript number 6 indicates a carbon atom of atomic mass 12 and atomic number 6, the difference being equal to the number of neutrons present in the nucleus.
www.atomicarchive.com /Glossary/Glossary1.shtml   (1027 words)

  
 List of elements by atomic number - Wikipedia, the free encyclopedia
[209], indicates the mass number of the longest-lived isotope of the element or characteristic isotopic composition.
Atomic weights of elements with atomic numbers from 1-109 taken from this source.
Atomic weights of elements with atomic numbers 110-116 taken from this source.
en.wikipedia.org /wiki/List_of_elements_by_number   (369 words)

  
 Atomic Structure and the Pascal Triangle
The number of protons in the nucleus (the "atomic number", Z) characterizes a chemical element.
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.
milan.milanovic.org /math/english/atom/atom.html   (820 words)

  
 AS unit foundation atomic structure page
The numbers of protons, electrons and neutrons in a particular isotope of a particular atom are given in a periodic table by the mass number and atomic number.
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).
www.rjclarkson.demon.co.uk /found/found2.htm   (832 words)

  
 atomic number - Encyclopedia.com
atomic number often represented by the symbol Z, the number of protons in the nucleus of an atom, as well as the number of electrons in the neutral atom.
Atomic numbers were first assigned to the elements c.1913 by H. Moseley; he arranged the elements in an order based on certain characteristics of their X-ray spectra and then numbered them accordingly.
The elements are now arranged in the periodic table in the order of their atomic numbers.
www.encyclopedia.com /doc.aspx?id=1E1:atomicnu   (549 words)

  
 AllRefer.com - atomic number (Chemistry) - Encyclopedia
atomic number, often represented by the symbol Z, the number of protons in the nucleus of an atom, as well as the number of electrons in the neutral atom.
Atomic numbers were first assigned to the elements c.1913 by H. Moseley; he arranged the elements in an order based on certain characteristics of their X-ray spectra and then numbered them accordingly.
The elements are now arranged in the periodic table in the order of their atomic numbers.
reference.allrefer.com /encyclopedia/A/atomicnu.html   (199 words)

  
 How do I find the number of protons, electrons and neutrons that are in an atom of...?
The atomic number is the number of protons in an atom of an element.
The atomic weight is actually a weighted average of all of the naturally occurring isotopes of an element relative to the mass of carbon-12.
That is the number of neutrons in an atom of krypton.
education.jlab.org /qa/pen_number.html   (840 words)

  
 Atomic Number | World of Chemistry
Atomic number is defined as the number of protons in the nucleus of an atom.
He assigned atomic numbers to the elements in such a way as to reflect the regular, integral, linear relationship of their x-ray spectra.
It soon came to be understood that the atomic number of an atom is equal to the number of protons in the atom's nucleus.
www.bookrags.com /research/atomic-number-woc   (522 words)

  
 atomic number --  Encyclopædia Britannica   (Site not responding. Last check: )
Accordingly, the number of protons, which is always equal to the number of electrons in the neutral atom, is also the atomic number.
Thus the effective atomic number of the cobalt atom in the complex [Co(NH3)6]3+ is 36, the sum of the number of electrons in the...
The mass number is commonly cited in distinguishing among the isotopes of an element, all of which have the same atomic number (number of protons) and are represented by the same literal symbol; for example, the two best known isotopes of uranium (those with mass numbers...
www.britannica.com /eb/article-9010131   (886 words)

  
 Atomic Theory   (Site not responding. Last check: )
The Atomic Mass Number of an atom is the total number of protons and neutrons in the nucleus of the atom.
The Atomic Number of an element is the number of protons or positive charges which are present in the nucleus of the atoms of that element.
The atomic volume of an element is the relative atomic mass of the element divided by is density.
www.ucc.ie /ucc/depts/chem/dolchem/html/dict/atom.html   (1217 words)

  
 List of Elements of the Periodic Table - Sorted by Atomic Number
Atomic number: The number of protons in an atom.
Atomic mass: The mass of an atom is primarily determined by the number of protons and neutrons in its nucleus.
Isotope of an element is defined by the sum of the number of protons and neutrons in its nucleus.
www.science.co.il /PTelements.asp   (516 words)

  
 Atomic Number - Search Results - MSN Encarta   (Site not responding. Last check: )
Atomic Number, symbol Z, the number of protons present in the nucleus of an atom, and the position of the corresponding element in the periodic...
Mass Number, in physics, the combined number of protons and neutrons in the nucleus of an atom (Atom).
- number of protons in atom: the number of protons in the nucleus of an atom of an element and its isotopes, used to determine that element's position in the periodic table
uk.encarta.msn.com /Atomic_Number.html   (143 words)

  
 atomic concepts
MU #2 The average atomic mass of an element is the weighted average of the masses of its naturally occurring isotopes.
The average atomic mass of an element is close to the mass of the most abundant isotope.
The average atomic mass of H is 1.00794 amu and it is calculated from H-1, H-2, and H-3.
www.chemcool.com /regents/atomicconcepts/aim5.htm   (844 words)

  
 Lesson 3-3 Atomic Structure   (Site not responding. Last check: )
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 mass number, which is given the symbol A in elemental notation, consists of the total number of protons and neutrons in the nucleus of the atom.
www.fordhamprep.com /gcurran/sho/sho/lessons/lesson33.htm   (942 words)

  
 Atomic Nomenclature   (Site not responding. Last check: )
he atomic number of an atom is essentially the number of protons in its nucleus.
This is because an atom is defined by its number of protons, not it's number of neutrons.
The reason that the atomic masses are not whole numbers is because the atomic masses of the isotopes are averaged to get the overall atomic mass for the element.
library.thinkquest.org /17940/texts/atomic_nomenclature/atomic_nomenclature.html   (548 words)

  
 What Are Atomic Number and Atomic Weight?
The number of protons in the nucleus of the atom.
The number of protons in a nucleus is called the atomic number and always equals the number of electrons in orbit about that nucleus (in a nonionized atom).
Its chemical behavior is determined by the atomic number 2 (the number of protons), which equals the normal number of electrons; the stability of its nucleus (that is, its radioactivity) varies with its atomic weight (approximately equal to the number of protons and neutrons).
www.eh.doe.gov /ohre/roadmap/achre/intro_9_3.html   (1009 words)

  
 Atomic Shorthand
The atomic number is the number of protons in an atom (which equals the number of electrons).
Atomic number of an element = the number of protons (which equals the number of electrons) in each atom of the element.
Mass number = the number of protons + the number of neutrons in an atom.
www.crocodile-clips.com /absorb/AC4/sample/LR303.html   (761 words)

  
 Introductory Terms, Page 2
The Atomic Number is the number of protons that are located in the nucleus of a given atom.
By international agreement, the upper case letter Z is used to represent the atomic numbers of all the elements.
Atomic weight is the decimal number most commonly associated with each element's symbol on the Periodic Chart.
www.bcpl.net /~kdrews/introterms/intro2.html   (823 words)

  
 ELEMENT - Definition
They are roughly divided into two great classes, the metals, as sodium, calcium, etc., which form basic compounds, and the nonmetals or metalloids, as oxygen, sulphur, chlorine, which form acid compounds; but the distinction is only relative, and some, as arsenic, tin, aluminium, etc., form both acid and basic compounds.
When the elements are tabulated in the order of their ascending atomic weights, the arrangement constitutes the series of the Periodic law of Mendelejeff.
The number of elements known is about seventy-five, but the gaps in the Periodic law indicate the possibility of many more.
www.hyperdictionary.com /dictionary/element   (611 words)

  
 Chemistry: WebElements Periodic Table : Periodic properties : Atomic number: Definition
Select from the menu to the left to view pictures illustrating the Atomic number.
The atomic number corresponds to the number of protons in the nucleus of an atom of that element.
It also corresponds to the number of electrons in the neutral atom.
www.webelements.com /webelements/properties/text/definitions/atomic-number.html   (161 words)

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