Answer Gold Beta & Alpha Decay Questions

[kirsten_2009]

Homework Statement

Use the periodic table to find the daughter nucleus after a gold nucleus (Au) undergoes beta decay. What would be the result if the gold nucleus had undergone alpha decay instead?

Homework Equations

The Attempt at a Solution

Beta Decay: A=196.96655 Z=80 Au

Alpha Decay: A=192 Z=77 Ir

I have a couple of questions regarding radioactive decay...is it accurate to say that all beta decays for all radioactive elements results in the loss of a neutron and the gain of a proton? So, the element's atomic number increases by 1 but the mass number stays the same? Also, then is it accurate to say that all alpha decay for all elements results in 2 neutrons being loss and 2 protons being loss? So, all alpha decay results in another element different from the starting one? but beta stays the same element? Sorry for all the questions...I'm just not sure I get it. Thanks!

 

[Bystander]

Homework Statement

Use the periodic table to find the daughter nucleus after a gold nucleus (Au) undergoes beta decay. What would be the result if the gold nucleus had undergone alpha decay instead?

Homework Equations

The Attempt at a Solution

Beta Decay: A=196.96655 Z=80 Au

Alpha Decay: A=192 Z=77 Ir

I have a couple of questions regarding radioactive decay...is it accurate to say that all beta decays for all radioactive elements results in the loss of a neutron and the gain of a proton? So, the element's atomic number increases by 1 but the mass number stays the same? Also, then is it accurate to say that all alpha decay for all elements results in 2 neutrons being loss and 2 protons being loss? So, all alpha decay results in another element different from the starting one? but beta stays the same element? Sorry for all the questions...I'm just not sure I get it. Thanks!

You get it --- elements are identified by atomic number, not mass.

 

[kirsten_2009]

O.k thank-you...so my answer is correct then? Should I round to 197 for Au's mass number?

 

[Bystander]

You said, "Z=80." Which element in the periodic table is identified by Z=80?

 

[kirsten_2009]

Mercury but it's mass number is not the same as Gold's...? Is this like some "special mercury" that comes from radioactive gold?

 

[Bystander]

Had to check a table of isotopes --- Au¹⁹⁷ is a "stable" isotope, and its natural abundance is 100% (all naturally occurring gold is 197). Hg¹⁹⁷ is an unstable isotope of mercury that decays back to gold by electron capture with a half life around 4 days. You are being taught from a really weird textbook.

They gave you definitions for α and β decay processes: restating them for you, α decay results in a loss of four atomic mass units and two atomic number units; β decay results in no change in mass and an increase of one in atomic number.

The exercise is just intended to get you used to how to skip backward or forward in the periodic table for the two decay processes without regard to whether the specific decays actually occur in nature.

Is this like some "special mercury"

It's an isotope --- the teaching materials you're working from may present you with isotopes that don't even exist given that they've already asked you to look at alpha and beta decays of Au¹⁹⁷. Iridium and mercury, and neither decay process actually occurs.

The odd numbers you see for atomic mass (196.______) are averages of the isotopic masses x abundances of those masses in a sample of a particular element, so don't let them throw you.

 

[kirsten_2009]

Thanks for the help! So really my answer should be...

Beta Decay: A=197 Z=80 Hg

Alpha Decay: A=193 Z=77 Ir

 

[Bystander]

Yup.