Homework on Radioactivity.

[saunj07]

Hi, everyone. I am currently busy with an assignment at school. Am doing these questions tomorrow in school so if you can help in any way i really would be great full.

Show what happens when:

 

(1) ---> An alpha particle is given off by plutonium-239

(2) ---> A beta particle is given off by iodine-131

 

Suppose that carbon-14 makes up 8% of the carbon in living plants and that the half-life of Carbon is 5700 years.

---> How long will it take for the % of Carbon-14 to fall from 8% to 4%

---> How old is a specimen that has 1% carbon-14

Any help would be greatly appreciated! Thanks in advance.

 

[Rhiaden]

For the carbon-14 question, make sure you understand what is meant by half-life. Half life is the time for half the quantity to decay.

Edited November 15, 2010 by Rhiaden

[saunj07]

Hi, I understand what you trying to say but basicly I have not been taught anything on this section. Our school gives us this assignment for us to try get the stuff ourselves. I have looked on the net for help but honestly cannot grasp the concept.

[swansont]

You have several different quantities that are conserved, such as charge (Z) and nucleon number (A) which are denoted in the [math]{_Z^A}X[/math] notation, where X is the chemical symbol. If an isotope were to emit a proton (H-1), the charge of the parent would be reduced by 1, and the nucleon number would be reduced by one. The total charge can't change, and you have to have the same number of nucleons — they can't just disappear all by themselves. All of the numbers on each side of the reaction are constant.

 

[math]{_Z^A}X \rightarrow {_{Z-1}^{A-1}}X + {_1^1}H[/math]

 

The same concept applies to alpha decay

 

Beta decay is slightly more complicated, because an electron will be accompanied by an antineutrino, which has no charge and A=0. The beta is denoted by [math]{_{-1}^0}e[/math]

[physics confusion]

 

swansont

Posted 16 November 2010 - 06:55 AM

 

You have several different quantities that are conserved, such as charge (Z) and nucleon number (A) which are denoted in the notation, where X is the chemical symbol. If an isotope were to emit a proton (H-1), the charge of the parent would be reduced by 1, and the nucleon number would be reduced by one. The total charge can't change, and you have to have the same number of nucleons — they can't just disappear all by themselves. All of the numbers on each side of the reaction are constant.

 

 

The same concept applies to alpha decay

 

Beta decay is slightly more complicated, because an electron will be accompanied by an antineutrino, which has no charge and A=0. The beta is denoted by

 

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JUst stepping in here to identify that during alpha decay, a helium nucleus is emmited from the nucleus, not a hydrogen atom like the above formula. during the alpha decay, a helium nucleus, doublely positively charged helium nucleus is emitted along with one or more gamma rays, decreasing the atomic number by 2 and the mass number by 4. eg/U-234----->Th-230+alpha particle+energy(gamma ray).