what trend is observed amont the atomic radii of main group elements across a period?
99942
Yes, atomic radii decrease as one goes across a period.  This is because as you go across a period, the atomic number increases.  As the number increases, the number of protons increase.  When the number of protons increase, the amount of pull that the nucleus exerts on the surrounding electrons goes up as well.  When the pull that the nucleus exerts (called "effective nuclear force") goes up, the electrons are pulled tightly closer to the nucleus.  For example, sodium has a bigger radius than chlorine because they are in the same period and chlorine has more protons, which means it pulls the electrons closer in, thus reducing the atom's radius.
747425
I suppose mass is a fairly easily measured value. Compared to finding the number of atoms, it's easier to just stick a sample on a scale/balance and weigh it.\n\nAnd the masses provided on the periodic table are weighted averages of the different isotopes found in nature.
30888
I'm not really sure what you mean, but here's a good site to look at the periodic table.\n\nhttp://en.wikipedia.org/wiki/Periodic_table
727822
It is 63 x 0.66 + 65 x 0.34.  Do you see why?  The actual atomic weight found in the periodic table will differ from this by a tad because of nuclear binding energy.
855090
S\n  * Group in periodic table: 16\n    * Group name: Chalcogen\n    * Period in periodic table: 3\n    * Block in periodic table: p-block\nFind the rest here --> http://www.webelements.com/webelements/scholar/
46678
The most popular atomic geometries are Linear, Trigonal Planar, Octahedral and Tetrahedra.\n\nI've added a link to a visualization program, though I couldn't get the plug-in to work.
714340
look up the periodic table...duh
476156
The Periodic Table of the Elements, as developed by Mendeleev.
622407
atomic radii inc. down the gr. n dec. from left to right.So Mg comes before Fe that's y Mg has bigger radius
923272
There are various trends/properties observable in the periodic table of elements:\n1. The elements in a column have same number of electrons in the outermost orbit of the atom. And this number is same as the column number. e.g. column no. 7 has elements (Fluorine, chlorine, bromine, iodine, astatine) that have exactly 7 electrons in their outermost orbit.\n2. The last column (8) are all inert gases.\n3. First three columns are metalic (conductors), last four are insulators, the middle (4th) is semiconductor (with Carbon and Silicon).\n4. The number assigned to an element is same as no.of protons in the nucleus of the atom.\n5. As the atomic number increases, weight of element increases. Thus Hydrogen is the lightest of all. Also first few are gases, then liquids, then light metals, then heavy metals.\n6. First two columns are rare earths and earths.\n7. After and including Uranium (92), all elements are radioactive.\n\nYou can find more info online.
745499
Go to Google scearch you will find lot of papers on this.\nCopy with changes from all the papers.\nIncluding whatever Mathamatical figures you find
93031
Check this out...\n\nhttp://home.inter.net/eds/paper/inchmetric.html
885270
Atomic number\n 8\n \nAtomic mass\n 15.999 g.mol -1\n \nElectronegativity according to Pauling\n 3.5\n \nDensity\n 1.429 kg/m3 at 20°C\n \nMelting point\n -219 °C\n \nBoiling point\n -183 °C\n \nVanderwaals radius \n 0.074 nm\n \nIonic radius\n 0.14 nm (-2)\n \nIsotopes\n 4\n \nElectronic shell \n [ He ] 2s 2 2p 4\n \nEnergy of first ionisation\n 1314 kJ.mol -1\n \nEnergy of second ionisation\n 3388 kJ.mol -1\n \nEnergy of third ionisation\n 5300 kJ.mol -1\n \nDiscovered by\n Joseph Priestly in 1774
313987
Oxygen will hv higher IE. IE increases on moving left to right in a period and decreases on moving top to bottom in a group. So elements with higher IE are in the top and right corner of the periodic table.
884906
the measure of an element 2 combine with other is called VALENCY.to work out the valenceys for certain chemicals we havta see the no. of atoms in outer & inner orbits..>>&then use the formula>>.hope it'll help u.
692251
A quick rule of thumb is; \nAs you go down and to the right on the Periodic Chart, you get a larger Atomic weight.  There is a direct correlation between Atomic Weight and Atom size.
978040
Or . . . 6.023 X 10 to the 23rd atoms.\n\nGet an "A".