NationStates Jolt Archive

No offense if you are an actual chemistry nerd. ;)

I desperately need your help at defining radioactivity, as I've searched wikipedia and didn't quite understand the definition. Also, I'd like to know if a radioactive molecule remains radioactive always during it's half-life decaying. Basically, does it stop being radioactive at any time during or after its decay?

Thanks a million, anyone who decides to help me.

No offense if you are an actual chemistry nerd. ;)

I desperately need your help at defining radioactivity, as I've searched wikipedia and didn't quite understand the definition. Also, I'd like to know if a radioactive molecule remains radioactive always during it's half-life decaying. Basically, does it stop being radioactive at any time during or after its decay?

Thanks a million, anyone who decides to help me.

http://www.wpbschoolhouse.btinternet.co.uk/page03/3_54radio.htm

No offense if you are an actual chemistry nerd. ;)

I desperately need your help at defining radioactivity, as I've searched wikipedia and didn't quite understand the definition. Also, I'd like to know if a radioactive molecule remains radioactive always during it's half-life decaying. Basically, does it stop being radioactive at any time during or after its decay?

Thanks a million, anyone who decides to help me.
Hi, I'm not sure if Im a nerd but I will help you.
When a molecule is radio active it emits particles. These particles are either alpha (electrons) or beta (helium nucluei). (There are also gamma particle but lets not worry about that.) If you have a sample of say 100 molecules the half life is the time it takes for half of those molecules to emit either an alpha particle or a beta particle. After 1 half life has passed 50 of the molecules have changed into another type of molecule. That new molecule may also be radioactive or it may not be radioactive. For the 50 molecule that didnot decay they will go through anouth half life and half of them will emit an alpha or beta particle. So you are left with 25 molecules of the original material. Then there will be another ahlf life and so on and so on, with number of molecules going 25, 13, 7, 4, 2, 1, 1, 0 or something like that.

Hi, I'm not sure if Im a nerd but I will help you.
When a molecule is radio active it emits particles. These particles are either alpha (electrons) or beta (helium nucluei).

Strike that, reverse it. Beta particles are electrons, alpha are helium nucluei (2 protons 2 neutrons).[/QUOTE]

The simple and most brief explanation is that....atoms are made of "stuff" (protons, neutrons, and electrons). This "stuff" is held together by a form of energy called "binding energy".

However some of these atoms are simply just too heavy, they fall apart. When a heavy atom falls apart, it falls into another smaller atom (or several), and inevitably there's some of this "stuff" left over. This extra stuff goes flying out in the form of alpha and beta radiation. Additionally when these heavy atoms fall apart, some of that energy holding it all together gets let go too, in the form of gamma particles (photons, pure energy).

Also, I'd like to know if a radioactive molecule remains radioactive always during it's half-life decaying

Well you don't really want to use the term "molecule" here, you want "atom" (molecules are made of atoms). A individual atom does not have a period of "half life" exactly. the description above is a pretty good one.

Let's say you have a big brick of uranium. Which is made of uranium atoms. The "half life" of the uranium is the time it takes for half of that uranium to decay, giving off radiation. Now atoms are ALWAYS decaying, it's not like if uranium has a half life of a day then that uranium is perfectly safe for 23 hours and 59 minutes then suddenly gives off a whole ton of radiation. It's always radioactive (until all the radioactive material is gone).

Half life means, generally, roughly how long it will take for half of the uranium to decay.

radioactive elements are ones that are emitting particles (either alpha, beta, or gamma) as a part of a radioactive decay. The half life is the amount of time it takes for half of a mass to decay. The amount of material never reaches zero. (Think of that as a limit).

The amount of material never reaches zero. (Think of that as a limit).

well...in theory it will eventually...half lives will continue to cut in half the amount of material until you're left with a single atom. It may take a tremendously long time for EVERY SINGLE atom in a radioactive material to decay, but it will happen EVENTUALLY. So "never" is not a literally good word, although for practical purpose the amount of material won't reach zero in any time frame that is worth discussing.

Strike that, reverse it. Beta particles are electrons, alpha are helium nucluei (2 protons 2 neutrons).

The simple and most brief explanation is that....atoms are made of "stuff" (protons, neutrons, and electrons). This "stuff" is held together by a form of energy called "binding energy".

However some of these atoms are simply just too heavy, they fall apart. When a heavy atom falls apart, it falls into another smaller atom (or several), and inevitably there's some of this "stuff" left over. This extra stuff goes flying out in the form of alpha and beta radiation. Additionally when these heavy atoms fall apart, some of that energy holding it all together gets let go too, in the form of gamma particles (photons, pure energy).



Well you don't really want to use the term "molecule" here, you want "atom" (molecules are made of atoms). A individual atom does not have a period of "half life" exactly. the description above is a pretty good one.

Let's say you have a big brick of uranium. Which is made of uranium atoms. The "half life" of the uranium is the time it takes for half of that uranium to decay, giving off radiation. Now atoms are ALWAYS decaying, it's not like if uranium has a half life of a day then that uranium is perfectly safe for 23 hours and 59 minutes then suddenly gives off a whole ton of radiation. It's always radioactive (until all the radioactive material is gone).

Half life means, generally, roughly how long it will take for half of the uranium to decay.

To complicate things a bit further some atoms will capture one of their electrons and emit a positron.

To complicate things a bit further some atoms will capture one of their electrons and emit a positron.

oy let's not get into anti matter. The OP wants a basic primer on radioactive decay so that discussion goes way beyond "the basic"

oy let's not get into anti matter. The OP wants a basic primer on radioactive decay so that discussion goes way beyond "the basic"

No antimatter here. Just orbital electron capture. Some elements decay through that route.

http://hyperphysics.phy-astr.gsu.edu/hbase/nuclear/radact2.html#c3

No antimatter here.

and emit a positron.

Unless I am mistaken isn't a positron a positively charged electron, making it the anti matter equivalent of an electron?

Which doesn't make much sense anyway from a physics standpoint....are you sure you don't mean emit a neutrino? I"m 99% sure positrons are not emitted in this fashion, I'm pretty sure it's neutrinos, not positrons that are emitted in electron capture.

Edit: yup, from your link: Electron capture is one form of radioactivity. A parent nucleus may capture one of its orbital electrons and emit a neutrino.

Unless I am mistaken isn't a positron a positively charged electron, making it the anti matter equivalent of an electron?

Which doesn't make much sense anyway from a physics standpoint....are you sure you don't mean emit a neutrino? I"m 99% sure positrons are not emitted in this fashion, I'm pretty sure it's neutrinos, not positrons that are emitted in electron capture.

Fuck, you're right. My bad. I blame multitasking.

OK, looks like we probably helped this kid out with chem. Now does anyone have a question relating to C or MATLAB?

Oh, my head hurts now...:confused:

Just kidding, that actually helps a lot, I'm done now, anyways, but thanks again.

Radiation is what happens to a cat when you put it in the microwave.

I don't know about everyone else, but in my school radioactivity is Physics, not Chemistry.

The thing to remember about radioactivity is its all about probability.

Each radioactive atom is unstable. If it is really unstable it will be more likely to "fall apart" sooner. Each atom of the same element with the same atomic weight will be equally stable. The tricky bit is that you never know exactly when each individual atom is going to decay. So you have to deal with averages.. hence half life.

On average after a certain amount of time half of the atoms will have undergone decay. That time is called the half life... but you can never say exactly which atoms will make up the half that decays and which will stay in their current form.

I don't know about everyone else, but in my school radioactivity is Physics, not Chemistry.
Same here ;) Though any self-respecting chemistry-geek should be able to define radioactivity, too ;)

Not NS: Homework Help forum, ffs.

I need to learn more of the periodic table before I qualify for "Chemistry Nerd", but I'm stuck. Is it Rubidium, Strontium, Yttrium; or Strontium, Rubidium, Yttrium; or something else entirely? Where does Nb come in?

Nobody mention neutron radiation? :( That's my favorite. Free neutrons have no charge and so are not repelled by nuclei. That's partially what makes it so darn dangerous. Neutron radiation is more penetrating than alpha or beta and in some cases even gamma. It also can do more damage than any other because it can cause non-radioactive materials to radiate by striking the nuclei and pushing them into an unstable isotope. It can usually be held in check by anything with lots of hydrogen in it like a water jacket or paraffin. When water is used you end up with heavy water which is actually toxic if you drink too much but fun to use at parties because you can make icecubes that sink in normal water.

Nobody mention neutron radiation? :( That's my favorite. Free neutrons have no charge and so are not repelled by nuclei. That's partially what makes it so darn dangerous. Neutron radiation is more penetrating than alpha or beta and in some cases even gamma. It also can do more damage than any other because it can cause non-radioactive materials to radiate by striking the nuclei and pushing them into an unstable isotope. It can usually be held in check by anything with lots of hydrogen in it like a water jacket or paraffin. When water is used you end up with heavy water which is actually toxic if you drink too much but fun to use at parties because you can make icecubes that sink in normal water.

I propose a heavy-watermelon.

I don't know about everyone else, but in my school radioactivity is Physics, not Chemistry.

Its both, we went over radioactivity in second semester general chemistry....