Predict whether each of the following nuclides is stable or unstable (radioactive). If the nuclide is unstable, predict the type of radioactivity you would expect it to exhibit. a. \({ }_{19} \mathrm{~K}\) b. \({ }_{26}^{56} \mathrm{Fe}\) c. \({ }_{11}^{20} \mathrm{Na}\) d. \({ }_{81}^{194} \mathrm{Tl}\)

Short Answer

Expert verified
a. Cannot predict stability and decay type without a given mass number. b. \({ }_{26}^{56} \mathrm{Fe}\) is stable. c. \({ }_{11}^{20} \mathrm{Na}\) is unstable and undergoes beta-minus decay. d. \({ }_{81}^{194} \mathrm{Tl}\) is unstable and undergoes beta-minus decay.

Step by step solution

01

Identify the number of neutrons and protons

The element is Potassium (K) with 19 protons.
02

Calculate the neutron-to-proton ratio

Since there are 19 protons, the neutron to proton ratio will be approximately 1:1, hence we expect 19 neutrons.
03

Determine stability and decay type

Given that there is only the atomic number and no mass number provided, we cannot predict a specific nuclide's stability or decay type in this case. b. \({ }_{26}^{56} \mathrm{Fe}\)
04

Identify the number of neutrons and protons

For \({ }_{26}^{56} \mathrm{Fe}\), there are 26 protons and (56-26) = 30 neutrons.
05

Calculate the neutron-to-proton ratio

The neutron-to-proton ratio is 30:26, approximately 1.15:1.
06

Determine stability and decay type

Iron-56 is stable as it is lighter than the maximum stability line (Z < 20), and its neutron-to-proton ratio is close to 1:1. c. \({ }_{11}^{20} \mathrm{Na}\)
07

Identify the number of neutrons and protons

The nuclide has 11 protons and (20-11) = 9 neutrons.
08

Calculate the neutron-to-proton ratio

The neutron-to-proton ratio is 9:11, or approximately 0.82:1.
09

Determine stability and decay type

Sodium-20 is unstable, given its N:Z ratio falls on the low side of the curve. It will undergo beta-minus decay, as there are more protons than desired, and a neutron will be converted to a proton. d. \({ }_{81}^{194} \mathrm{Tl}\)
10

Identify the number of neutrons and protons

The nuclide has 81 protons and 194 - 81 = 113 neutrons.
11

Calculate the neutron-to-proton ratio

The neutron-to-proton ratio is 113:81, or approximately 1.39:1.
12

Determine stability and decay type

This nuclide is unstable. Due to its high proton number, it is likely to undergo beta-minus decay.

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