In a helium atom, which contains two electrons, do you think that on average the electrons are closer to the nucleus or farther away than in a hydrogen atom? Why?

Which of the following forces is (most) crucial for holding a nucleus together?

(a) electric force

(b) magnetic force

(c) the strong force

(d) friction

(e) gravity

An example of a "pick-up" nuclear reaction is $_{2}^{3} \mathrm{He}+ _{6}^{12} \mathrm{C} \rightarrow \mathrm{X}+\alpha .$ What is the resulting nucleus?

Describe how eukaryotic cells are able to keep such large amounts of DNA in the small volume of the cell nucleus. (Hint Review the structure of a chromosome in Chapter 10.)

Calculate the nuclear binding energy of the nucleus ${ }_{11}^{23} \mathrm{Na}$. The measured atomic mass of $\frac{23}{11} \mathrm{Na}$ is $22.989767$ amu.

The element oxygen has three naturally occurring isotopes, with 8, 9, and 10 neutrons in the nucleus, respectively. Write the full chemical symbols for these three isotopes.

Give the number of protons and number of neutrons in the nucleus of each the following: (16.1) a. sodium-25 b. nickel-61 c. rubidium- 84 d. silver-110

Find the energy to remove (a) one proton and (b) one neutron from a ${ }^{32} \mathrm{~S}$ nucleus. (c) Explain the difference between your answers to parts (a) and (b).

When a nucleus undergoes either $\beta^{-}$ or $\beta^{+}$ decay, what happens to the energy levels of the atomic electrons? What is likely to happen to these electrons following the decay?

Is it possible for the de Broglie wavelength of a "particle" to be greater than the dimensions of the particle? To be smaller? Is there any direct connection? Explain.

Near the surface of the nucleus of a lead atom, the electric field has a strength of $3.4 \times 10^{21} \mathrm{~V} / \mathrm{m}$. What is the energy density in this field?

Show that the magnetic dipole moment M of an electron orbiting the proton nucleus of a hydrogen atom is related to the orbital momentum $L$ of the electron by

$$M=\frac{e}{2 m} L.$$

Thorium-231 is the product of alpha emission. It is radioactive and emits beta radiation. Determine (a) the parent nucleus of Th-231. (b) the daughter product of Th-231 decay.

What is the energy of the $\alpha$ particle emitted in the decay ${ }^{2104} \mathrm{Po} \rightarrow{ }^{206} \mathrm{~Pb}+\alpha$ ? Take into account the recoil of the daughter nucleus.