#ATOMIC RADIUS CALCULATOR SERIES#

Notice that, within the series of positive ions, and the series of negative ions, that the ionic radii fall as you go across the period. Is this surprising? Not at all - you have just added a whole extra layer of electrons. The values are again for 6-co-ordination, although I can't guarantee that for the phosphide figure.įirst of all, notice the big jump in ionic radius as soon as you get into the negative ions. The values for the oxide and chloride ions agree in the different source, so it is probably OK. The phosphide ion radius is in brackets because it comes from a different data source, and I am not sure whether it is safe to compare it. The table misses out silicon which does not form a simple ion. Let's look at the radii of the simple ions formed by elements as you go across Period 3 of the Periodic Table - the elements from Na to Cl. The size of the atom is controlled by the 3-level bonding electrons being pulled closer to the nucleus by increasing numbers of protons - in each case, screened by the 1- and 2-level electrons. In the period from sodium to chlorine, the same thing happens. The amount of screening is constant for all of these elements. The increasing number of protons in the nucleus as you go across the period pulls the electrons in more tightly. (Look back to the left-hand side of the first diagram on this page if you aren't sure, and picture the bonding electrons as being half way between the two nuclei.)įrom lithium to fluorine, those electrons are all in the 2-level, being screened by the 1s 2 electrons. If you think about it, the metallic or covalent radius is going to be a measure of the distance from the nucleus to the electrons which make up the bond.

Leaving the noble gases out, atoms get smaller as you go across a period. You aren't comparing like with like if you include the noble gases. All the other atoms are being measured where their atomic radius is being lessened by strong attractions. Because neon and argon don't form bonds, you can only measure their van der Waals radius - a case where the atom is pretty well 'unsquashed'. You have to ignore the noble gas at the end of each period. It assumes that you understand electronic structures for simple atoms written in s, p, d notation. This page explains the various measures of atomic radius, and then looks at the way it varies around the Periodic Table - across periods and down groups. Trends in ionic radius for some more isoelectronic ions.Trends in ionic radius in the Periodic Table.Trends in atomic radius in Periods 2 and 3.Trends in atomic radius in the Periodic Table.Thats not what i got by calculating number of atomic sites using the equation: N=((Avogadros number)(Density))/(Atomic Wt) (2.11*10^19 Unit Cells in 1 m Cubed)(4 Atoms per FCC Unit Cell)= 8.43*10^19 atoms in 1m cubed? this hasnt given me the same answer as calculated before, 8.5X10^28. then multiplied this number by the number of atoms in a FCC unit cell, which is 4. I have taken the volume of 1m cubed divided by the volume of a FCC unit cell of copper, returning the number of unit cells in a cubic meter. How would i calculate atomic sites/meter cubed by just knowing the atomic radius of copper? For copper, the atomic radius is 128nm, i have used the formula N=((Avogadros number)(Density))/(Atomic Wt) to find that the number of atomic sites per meter cubed is about 8.5 X 10^28.

Atomic radius calculator