Karen

OK, great! Thank you guys so much!!!!!

Thank you, everyone, for your replies. This is for a high school chemistry class in which I've found that many of my student population are not interested in learning purely abstract things until I give them a concrete manifestation of the concept that they can identify with first. For example, when I talk about acidity, I tell them we can taste it. It tastes sour. When I talk about Grahams law of effusion, I uncap a jar of perfume and a jar of ammonia so they can smell that the lower molecular weight one diffuses to them faster. I tell them our skin is able to detect the kinetic energy of molecular motion - it feels hot. I tell them that we make daily use of exothermic chemical reactions when we heat our homes from the combustion of natural gas. When I talk about alpha decay, I tell them that's where all the helium for party balloons comes from on earth, because all the original helium floated away already. Unreactivity of some metals is what makes gold, silver, platinum and copper so ideal for jewelry and coins. Etc. I have to connect every chemistry concept to some real-world phenomena that the kids have direct experience with. So I'm looking for something students can see, feel, hear, taste, smell, use, wear, buy, or otherwise directly experience that demonstrates the phenomenon of atomic radius. Let me ask you this: I think helium balloons might lose volume more quickly than air balloons. Is that because helium has a small enough atomic radius to leak through the knot?

Can you elaborate with any specific examples?

No, I'm sorry. I meant what do people use this information you included for. I already know what the atomic radii, ionic radii and ionization energies are. I just need to know how people apply this knowledge to actual real world problems. Sorry for the confusion. I don't want to know what the atomic radii are. I want to know what good is knowing them. For example, complete these sentences: It is important to know atomic (or ionic) radius because once you know the atomic (or ionic) radius, you can use that information to _______. Chemists use information about an element's atomic radius so that they can _______________. Material scientists need information about atomic radii in order to __________. You can't _____________ unless you know the atomic radius of the elements involved. Once scientists figured out the atomic radii of the elements, that enabled them to ______________. Without knowing the atomic radii, scientists would not be able to _____________. Once scientists figured out atomic radii, that opened up a whole new world of being able to ____________.

Hi everyone, I'm trying to create a chemistry lesson on the trends in the periodic table and I'd like to demonstrate the real-world utility of knowing each of trend. I've been looking on the internet for hours with no luck. What do applied chemists actually USE atomic radius for? What are the APPLICATIONS of that knowledge? What VALUE does knowing atomic radius offer the world? Surely it must be good for something ..... right?