temperature and ionization

[lemur]

I am trying to understand the relationship between heat and chemical reactions. It seems like higher temperatures would be required to break stronger bonds and ionize particles that are closer to noble elements. Are substances this predictable and is it possible, for example, to make lists of molecules that break down at various temperatures; as well as ions that form? I would think that by making such lists, you could see which molecular re-configurations (is that just a fancy way of saying "chemical reaction?") were possible at specific temperatures?

[mississippichem]

I am trying to understand the relationship between heat and chemical reactions. It seems like higher temperatures would be required to break stronger bonds and ionize particles that are closer to noble elements. Are substances this predictable and is it possible, for example, to make lists of molecules that break down at various temperatures; as well as ions that form? I would think that by making such lists, you could see which molecular re-configurations (is that just a fancy way of saying "chemical reaction?") were possible at specific temperatures?

 

If you look at the periodic table, all the elements to the left have greater metallic properties, i.e. require a lower energy to be ionized. Elements to the far right (noble gases) require a lot more energy to be ionized.

 

This can be used to explain why, for example, alkali metals like sodium so easily tend to form 1+ charged ions. Take the familiar sodium chloride:

 

[ce] NaCl -> Na^{+} + Cl^{-} [/ce]

 

All I've done here is show you its constituent ions.

 

Sodium is so willing to give up an electron that sodium metal, [ce] Na^{0} [/ce], when put in water will react vigorously to give up an electron and form a [ce] Na^{+} [/ce] ion.

 

[ce] 2Na + 2H_{2}O -> 2NaOH + H_{2} [/ce]

 

I've really barely scratched the surface here but hopefully I'm pointing you in the right direction.

 

*These trends are all well defined and easily understandable for the s and p blocks of the periodic table. When you move into the d and f blocks though, the whole game gets quite counter-intuitive and spooky quantum effects become more significant. For the really heavy elements, electrons are moving so fast that even relativistic effects have a role to play.

Edited March 30, 2011 by mississippichem

[lemur]

If you look at the periodic table, all the elements to the left have greater metallic properties, i.e. require a lower energy to be ionized. Elements to the far right (noble gases) require a lot more energy to be ionized.

I was reading about that today and trying to generate some intuitive feel for how "electron bounty" results in ductility, malleability, and greater propensity to give up electrons. It's as if the electrons become more fluid when there are less of them in the shell. Is that because they can break away easier and thus "flow" between atoms more?

 

Sodium is so willing to give up an electron that sodium metal, [ce] Na^{0} [/ce], when put in water will react vigorously to give up an electron and form a [ce] Na^{+} [/ce] ion.

 

[ce] 2Na + 2H_{2}O -> 2NaOH + H_{2} [/ce]

I.e. at room temperature, you mean? So is it just that the hydrogen bonding in the surface temperature of the water creates enough kinetic energy among the particles to ionize the Na and "bump off" one of the hydrogens from the water? I.e. does the charge imbalance of the water result in ionization of the Na? Does the ionized Na then collide with the water at a speed to cause it to fragment into ionized constituents that are attracted to the Na ions for bonding? I'm trying to get a full picture of the mechanics of the process.

 

I've really barely scratched the surface here but hopefully I'm pointing you in the right direction.

you tell me. Are the Na-ionization and the water-ionization similar processes because of the amount of energy it takes to break off the relevant parts?

 

*These trends are all well defined and easily understandable for the s and p blocks of the periodic table. When you move into the d and f blocks though, the whole game gets quite counter-intuitive and spooky quantum effects become more significant. For the really heavy elements, electrons are moving so fast that even relativistic effects have a role to play.

Once I get a feel for the mechanical behaviors of the smaller atoms, maybe the "relativistic effects" you mention will be that much more interesting. Currently, I have yet to see regularities in the behaviors vis-a-vis the atomic structures because I don't know the behaviors.