The two ions $K^+}and $Ca^{2+}$ each have 18 electrons surrounding the nucleus. Which would you expect to have the smaller radius? Why?

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.)

Give the number of protons and number of neutrons in the nucleus of each of the following: (16.1) a. boron-10 b. zinc-72 c. iron- 59 d. gold-198

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?

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?

Consider the beta decay ${ }^{10} \mathrm{Be} \rightarrow{ }^{10} \mathrm{~B}+\beta^{-}$, with the beryllium nucleus initially at rest. (c) What are the possible energies of that other particle?

Is the mass of an atomic nucleus greater or less than the sum of the masses of the nucleons composing it? Why don't the nucleon masses add up to the total nuclear mass?

Calculate the mass defect for the neon-20 nucleus. The mass of neon-20 is $19.992440 ~u$. (Hint: How many protons and neutrons does neon-20 have?)

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).

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.

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

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

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?

What is the electric potential energy of a system that consists of two protons $2.5 \times 10^{-15} \mathrm{m}$ apart-as might occur inside a typical nucleus?