Consider the atoms ${}^{16}\text{O,}{}^{18}\text{O,}{}^{18}\text{F,}{}^{18}\text{Ne,}$ and ${}^{20}\text{Ne}$. Some of the following questions may have more than one answer. Give all answers that apply.

1. Which are isotopes?

2. Which are isobars?

3. Which have the same chemical properties?

4. Which have the same number of neutrons?

1. Is the binding energy of a nucleus with $A=200$ more than, less than, or equal to the binding energy of a nucleus with $A=60?$ Explain.

2. Is a nucleus with $A=200$ more tightly bound, less tightly bound, or bound equally tightly as a nucleus with $A=60?$ Explain.

1. How do we know the strong force exists?

2. How do we know the strong force is short range?

Does each nuclear energy-level diagram in FIGURE Q42.4 represent a nuclear ground state, an excited nuclear state, or an impossible nucleus? Explain.

FIGURE Q42.4

Are the following decays possible? If not, why not?

1. ${}^{232}\text{Th}(Z=90)\to {}^{236}\text{U}(Z=92)+\alpha$

2. ${}^{238}\text{Pu}(Z=94)\to {}^{236}\text{U}(Z=92)+\alpha$

3. ${}^{11}\text{B}(Z=5)\to {}^{11}\text{B}(Z=5)+\gamma$

4. ${}^{33}\text{P}(Z=15)\to {}^{32}\text{S}(Z=16)+\text{e}{}^{-}$

Nucleus A decays into nucleus B with a half-life of 10 s. At $t=0\text{s,}$ there are 1000 A nuclei and no B nuclei. At what time will there be 750 B nuclei?

What kind of decay, if any, can occur for the nuclei in FIGURE Q42.7?

FIGURE Q42.7

Apple A in FIGURE Q42.8 is strongly irradiated by nuclear radiation for 1 hour. Apple B is not irradiated. Afterward, in what ways are apples A and B different?

FIGURE Q42.8

The three isotopes ${}^{212}\text{Po,}{}^{137}\text{Cs,}$ and ${}^{90}\text{Sr}$ decay as ${}^{212}\text{Po}\to {}^{208}\text{Pb }+\alpha {\text{, }}^{137}\text{Cs}\to {}^{137}\text{Ba}+e^{-}+\gamma$, and ${}^{90}\text{Sr}\to {}^{90}\text{Y}+e^{-}$. Which of these isotopes would be most useful as a biological tracer? Why?