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Topic: Atomic radius

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  Atomic radius - Wikipedia, the free encyclopedia
The atomic radius is the distance from the atomic nucleus to the outmost stable electron orbital in an atom that is at equilibrium.
Technically, the atomic radius is one half of the equilibrium internuclear distance between two adjacent atoms (which may either bonded covalently or present in a closely packed crystal lattice) of an element.
In simpler terms, it roughly means that the atomic radius is half the distance between the nuclei of two adjacent atoms.
en.wikipedia.org /wiki/Atomic_radius   (289 words)

 Atomic Radii
Atomic size (proportional to the distance over which there is appreciable electron density) increases as we go from He to Ne to Ar.
Nonetheless, atomic radii are tabulated and serve as a useful predictive concept in chemistry.
The atomic radii are often called the covalent radii (because the bonds between atoms are purely covalent).
www.chemistry.ohio-state.edu /~woodward/ch121/ch7_radius.htm   (1065 words)

 UNIT 4 - PERIODIC TABLE   (Site not responding. Last check: 2007-10-22)
The atomic radius is a periodic property of the elements.
The relation between atomic radius and atomic number can be interpreted in terms of the arrangement of electrons in the orbitals of atoms and in terms of nuclear charge.
The normal covalent radius is the effective distance from the center of the nucleus to the outer valence shell of that atom in a typical covalent or coordinate bond.
dwb.unl.edu /Chemistry/LearningObjectives/NY04.html   (2326 words)

 Atomic Size
The radius of the tire is different when measured to the top of the tire than when measured to the bottom of the tire resting on the ground.
So as you go across a period, the increase in the nuclear charge causes a decrease in the atomic size because the electrons in the valence energy level are pulled in closer and closer.
In a sense, it would be like using atomic radii for the metals and an average of covalent and van der Waals radii for the nonmetals.
dl.clackamas.cc.or.us /ch104-07/atomic_size.htm   (1292 words)

 Periodicity of Atomic Properties
The atomic radius is determined by the effective volume of the outermost electronic level, and not by the size of the nucleus.
The radius of anions is always larger than the covalent radius of the atoms from which they are derived, as shown in the figure on the right, which applies to the Group VII elements.
The van der Waals radius is the radius of the spherical space occupied by an atom when it is bonded to another atom by van der Waals forces.
www.physchem.co.za /Atomic/Periodicity.htm   (1122 words)

 Index   (Site not responding. Last check: 2007-10-22)
The metallic radius is half the distance between the centres of neighbouring atoms in a metal.
The covalent radius is the smaller of the two and this is expected as, in the molecule, the atoms are pulled together by their attraction for the electrons shared in the bond between them.
For example, the distance between the magnesium cation and the oxide anion in magnesium oxide is 0.211 nm, the radius of the Mg ion is calculated from 0.205 nm - 0.146 nm = 0.065 nm.
www.chemit.co.uk /java/rsc_periodicity/index.htm   (690 words)

 atomic and ionic radius
The radius of an atom can only be found by measuring the distance between the nuclei of two touching atoms, and then halving that distance.
This measure of atomic radius is called the van der Waals radius after the weak attractions present in this situation.
Trends in atomic radius in Periods 2 and 3
www.chemguide.co.uk /atoms/properties/atradius.html   (925 words)

 The first property to explore is atomic radius.
To get the atomic radius we assume the distance between the two nuclei is the sum of two chlorine atomic radii.
Therefore the atomic radius of chlorine is 0.994 Å.
Atomic radii determine this way are also called covalent radii.
intro.chem.okstate.edu /1215/Lecture/Chapter11/Mon112398.html   (1268 words)

 Ionization Energy   (Site not responding. Last check: 2007-10-22)
In specifying values for the radius of an atom, one must keep in mind the fact that atoms are not hard spheres, and the electron distribution in the outer part of the atom does not have a sharp cutoff radius.
As might be expected, the ionic radius of negative ions is slightly larger than the covalent radius since they have extra electronic charge, and that of positive ions is slightly smaller.
The atomic radius is one of the parameters used in quantifying chemical bonds.
hyperphysics.phy-astr.gsu.edu /hbase/chemical/atomrad.html   (184 words)

 Elements, Atomic Radii and the Periodic Radii
Atomic radii represent the sizes of isolated, electrically-neutral atoms, unaffected by bonding topologies.
The general trend is that atomic sizes increase as one moves downwards in the Periodic Table of the Elements, as electrons fill outer electron shells.
The covalent radius of an atom can be determined by measuring bond lengths between pairs of covalently-bonded atoms: if the two atoms are of the same kind, then the covalent radius is simply one half of the bond length.
www.crystalmaker.co.uk /support/tutorials/crystalmaker/AtomicRadii.html   (1068 words)

 Atomic Radius   (Site not responding. Last check: 2007-10-22)
Atomic radius is taken as the covalent radius for non-metallic elements and as the metallic radius for metals.
Covalent radius is one-half the distance between the nuclei of two identical atoms that are singly bonded to one another.
Atomic radii were taken from the 15th edition of LANGE'S HANDBOOK OF CHEMISTRY, J.A. Dean, Ed., McGraw-Hill, 1999.
genchem.chem.wisc.edu /lab/PTL/PTL/Properties/Atomrad.html   (123 words)

 Periodic Trends
Therefore, the atomic radius increases as the group and energy levels increase.
In this case, the radius of the cation is much smaller than its respective atom.
Since the square of the distance is inversely proportional to the force of attraction, lattice energy decreases as the atomic radius increases.
library.thinkquest.org /C006669/data/Chem/atomic/trends.html   (833 words)

 Atomic Radii
Basically, the atomic radii of noble gases are estimated using a variety of methods.
Argon's atomic radius can be estimated by freezing argon into a solid, which can be done easily using a fairly low-tech vacuum pump and liquid nitrogen (I've taught this experiment myself to students in a college physical chemistry lab).
For example, there are scattering experiments where you bang atomic beams together at various angles and use the scattering pattern to backtrack and estimate the size of the atom and the strength of the atomic forces.
www.newton.dep.anl.gov /askasci/chem00/chem00622.htm   (594 words)

 Re: what causes nitrogen to be different than oxygen/carbon (atomic radius)?
Atomic radius tends to go with first ionization energy; the higher the IE, the smaller the radius.
In atomic nitrogen, there are five valence electrons: two in the s orbital, and one in each of the three p orbitals.
In atomic oxygen, there are six valence electrons: two in the s orbital, one in each of three p orbitals, and one more which is jammed into one of the p orbitals with another electron.
www.madsci.org /posts/archives/Feb2003/1046354777.Ch.r.html   (526 words)

 Media Portfolio
Figure 5.1 A graph of atomic radius in picometers (pm) versus atomic number shows a rise-and-fall pattern of periodicity.
The atomic radius of an atom is taken to be one-half the distance between the nuclei of two of the same atoms bound to one another.
Atomic radii for individual atoms can then be used to predict the bond length between two different atoms.
wps.prenhall.com /wps/media/objects/602/616516/Chapter_05.html   (1497 words)

 The first property to explore is atomic radius.
We might be able to use that argument to explain the trend within a group, but when we look at the atomic radius trend going across a period the radius decreases.
Another way to explain the trend in atomic radius across a period is in terms of the effective nuclear charge experienced by the valence electrons.
Fluorine (atomic number 9) has a very negative electron affinity, energy is released when is gains an electron.
intro.chem.okstate.edu /1314F00/Lecture/Chapter7/Lec111300.html   (2187 words)

 SparkNotes: Atomic Structure: Periodic Trends
Now we are ready to discuss the periodic trends of atomic size, ionization energy, electron affinity, and electronnegativity.
The atomic size of an atom, also called the atomic radius, refers to the distance between an atom's nucleus and its valence electrons.
The nucleus of the atom gains protons moving from left to right, increasing the positive charge of the nucleus and increasing the attractive force of the nucleus upon the electrons.
sparknotes.com /chemistry/fundamentals/atomicstructure/section3.rhtml   (1341 words)

 Periodic Table
atomic radii increase with atomic number because the number of energy level increases.
atomic radii decrease when atomic number increases because the nuclear charges increase attracting electrons closer to the nucleus.
Using principles of atomic structure, explain why the Na ion is much smaller than the K ion.
www.chemcool.com /regents/periodictable/aim3.htm   (1136 words)

 Atomic radius   (Site not responding. Last check: 2007-10-22)
Atomic radius is the distance from the atomic nucleus to the outmost stable electron orbital in a atom that is at equilibrium and is measured in picometers or Angstroms.
Atomic radii are called covalent radii when referring to non-metallic elements and metallic radii when referring to metals.
See also: atomic number, atomic weight, covalent bonding
www.icyclopedia.com /encyclopedia/a/at/atomic_radius.html   (164 words)

 Atomic radii of the elements (data page) - Wikipedia, the free encyclopedia
Note: All measurements given are in picometres (pm).
The radius of an atom is not a uniquely defined property and depends on the definition.
Data derived from other sources with different assumptions cannot be compared.
en.wikipedia.org /wiki/Atomic_radii_of_the_elements_(data_page)   (175 words)

 Creative Chemistry - Trend in atomic radius of Group 2 elements
so the electrons in the outer energy levels are further from the nucleus and the atomic radius increases.
As the number of protons in the nucleus increases going down Group 2, you might expect the atomic radius to decrease because the nuclear charge increases.
This does not happen,  because although the electrons in the inner energy levels become closer to the nucleus, the factors described above have a greater influence on the atomic radius overall.
www.creative-chemistry.org.uk /alevel/module1/trends1.htm   (137 words)

 Periodic Trends   (Site not responding. Last check: 2007-10-22)
The atomic radius helps us predict may other characteristics about an element including how it will react with other elements.
Turn the page to Figure D. Figure D plots atomic radii vs. atomic number for the first half of the periodic table.
In general, what happens to atomic radius size as you proceed through a period from the alkali metals to the noble gases (left to right across the table)?
www.stillwater.k12.mn.us /~SwansonL/u6wsperi.htm   (518 words)

 [No title]   (Site not responding. Last check: 2007-10-22)
The atomic number and the element symbol are two alternate ways to label an element.
In nuclide symbols, the atomic number is a leading subscript; for example, in 126C, the "6" is the atomic numberatomic radiusmetallic radius; covalent radius; atomic radii.
The radius of atoms obtained from covalent bond lengths is called the covalent radius; the radius from interatomic distances in metallic crystals is called the metallic radius.atomic theoryAn explanation of chemical properties and processes that assumes that tiny particles called atoms are the ultimate building blocks of matter.Aufbau principleaufbau construction; building-up principle.
www.cdlilly.com /Vocabulary/VocabularyUnit2-AtomicStructure.doc   (1537 words)

 The Variation of Atomic Properties
These distances can be used to devise a table of atomic radii, which give fairly good approximations of the relative size of the atoms.
Plot atomic radius against atomic number as a line graph from the given table.
Would you expect the atomic radius to be larger or smaller for element 37 than for element 36?
educ.queensu.ca /~science/main/concept/chem/c07/c07las11.html   (497 words)

 Inert gases and atomic radius
Question: The atomic radius decreases from left to right on the periodic table except for the inert gases which are much larger than the halogens.
One way to see whether the guess is a good one is to try and use the guessed-at H radius and Cl radius to predict the bond length of HCl.
Now the reason why the radius decreases as you move across a period is the effective nuclear charge increases.
www.newton.dep.anl.gov /askasci/chem99/chem99004.htm   (400 words)

 Media Portfolio
As we move down a group in the periodic table the effective nuclear charge is essentially unchanged while the principal quantum number increases, resulting in an increase in the atomic radius.
Ionization energy is the energy required to remove an electron from the ground state of a gaseous atom or ion.
The first ionization energies of the elements generally increase from right to left across a row as a result of the increasing nuclear charge and decreasing atomic radius.
cwx.prenhall.com /petrucci/medialib/media_portfolio/10.html   (894 words)

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