CHE 105/110 Introduction to Chemistry - Exercises and Answers

1.

Define radioactivity.

1.

Radioactivity is the spontaneous emission of particles and electromagnetic radiation from nuclei of unstable atoms.

3.

How many protons and neutrons are in each isotope?

1. ${}_5{}^{11}\text{B}$

2. ${}_{13}{}^{27}\text{A}\text{l}$

3. ⁵⁶Fe

4. ²²⁴Rn

3.

1. 5 protons; 6 neutrons


2. 13 protons; 14 neutrons


3. 26 protons; 30 neutrons


4. 86 protons; 138 neutrons

5.

Describe an alpha particle. What nucleus is it equivalent to?

5.

An alpha particle is a collection of two protons and two neutrons and is equivalent to a helium nucleus.

7.

What are gamma rays?

7.

Gamma rays are high-energy electromagnetic radiation given off in radioactive decay.

9.

Plutonium has an atomic number of 94. Write the nuclear equation for the alpha particle emission of plutonium-244. What is the daughter isotope?

9.

${}_{94}{}^{244}\text{P}\text{u}\to {}_{92}{}^{240}\text{U}\text{ + }{}_2{}^4\text{H}\text{e; daughter isotope; <sup class="superscript">240</sup>U}$

11.

Tin has an atomic number of 50. Write the nuclear equation for the beta particle emission of tin-121. What is the daughter isotope?

11.

${}_{50}{}^{121}\text{S}\text{n}\to {}_{51}{}^{121}\text{S}\text{b + }{}_{-1}{}^0\text{e}\text{; daughter isotope; <sup class="superscript">121</sup>Sb}$

13.

Energies of gamma rays are typically expressed in units of megaelectron volts (MeV), where 1 MeV = 1.602 × 10⁻¹³ J. Using the data provided in the text, calculate the energy in megaelectron volts of the gamma ray emitted when radon-222 decays.

13.

0.51 MeV

15.

Which penetrates matter more deeply—alpha particles or beta particles? Suggest ways to protect yourself against both particles.

15.

Beta particles penetrate more. A thick wall of inert matter is sufficient to block both particles.

17.

Define nuclear fission.

17.

Nuclear fission is the breaking down of large nuclei into smaller nuclei, usually with the release of excess neutrons.