Do you use atomic radius in your work?

[Karen]

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?

[studiot]

Quote

 

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.

 

Hello Karen I think its a little more complicated than that, you should also consider ionic radius and ionisation energies.

Here are some trend diagrams.

They are usful in studying bonding and structural arrangements.

Edited April 5, 2019 by studiot

[Karen]

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 ____________.

Edited April 6, 2019 by Karen

[hypervalent_iodine]

2 hours ago, Karen said:

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 ____________.

 

Studiot mentioned what we use it for. It’s primarily useful in chemistry for predicting or explaining bonding interactions. You use it in structural biochemistry, crystallography, etc. You might also it to infer reactivity of certain elements. 

[Karen]

Can you elaborate with any specific examples?

[hypervalent_iodine]

For example, in structural biochemistry you can infer what sort of binding interactions exist between an amino acid residue and some sort of ligand / substrate by looking at atomic distances. By knowing the radii of the atoms you are measuring, you can make predictions about the presence / absence of intermolecular attractive forces, such as short contacts. 

In terms of reactivity, just think about the difference in ionisation energy between, say, sodium and caesium. Thinking about atomic radii and what that means about the distance from valence electrons to the nucleus, why might caesium’s first ionisation energy be lower?

These are all things that you might Google, so I would encourage you to do that and come back if you have questions.

[studiot]

11 hours ago, Karen said:

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:

I just rushed these to get something out as it was after midnight with me.

The important point was that atomic sizes, by themselves, are relatively uninteresting so I wanted to widen to ionic radii and also bring in molecules and regular solids (crystals) - and thus bond lengths where size has vastly greater importance.

Your list of questions seems to bear that approach out since, for instance, materials scientists almost never deal with individual atoms.

However I have a few questions.

Firstly is this list of question something you are preparing as a teacher for your students, or has the list been prepared for you as a student?

I am assuming, from your post,  that you are teacher and will therefore understand when I say that size in atoms will allow calculations about spin and orbital angular momenta but not rotational and vibrational data like with molecules, for spectroscopic purposes.

You will further understand that size indicates lattice distortion in a semiconductor or other material, which in turn indicates atoms that be substituted in the lattice or incorporated in the lattice interstitial voids.

So what is the discipline that this is intended for?

[Karen]

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?

[studiot]

5 hours ago, Karen said:

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? 

 

Yes we did tasting of acids when we started chemistry.

Yes helium is small enough to leak through even the fabric walls of a balloon. That is why they are silvered it is more than advertising puff.

Another example is methane which leaks through concrete floors but collects under steel roofs.
Methane is generated in old rubbish tips so this is a problem as it is imflammable and can get to explosive concetrations.

[hypervalent_iodine]

11 hours ago, Karen said:

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?

Great question, and not something I had thought of immediately, but something I am familiar with. In fact, it’s not so much the knot as it is the rubber of the balloon itself (as studiot mentioned). You have to buy balloons made of specific material for helium or it will rapidly deflate for this reason. You see the same with hydrogen, which is larger but still small enough that normal balloons are permeable to it. When I use hydrogen balloons in the lab, I use 2 helium quality rubber party balloons, one stuck inside the other, and seal the balloon around whatever tubing I’m using with rubber bands and film. You will still have a deflated balloon by the next day. The same balloon with argon or nitrogen gas will remain inflated. Probably an easy enough experiment to set up in class actually, if you have access to helium. 

[Karen]

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