Chemical reactions involve changing one substance into another substance by rearranging atoms. However, during a chemical reaction, atoms of one element cannot change into atoms of another element. The reason this change cannot occur is that chemical reactions only involve an atom's electrons – the nucleus remains unchanged. Recall that an atom's identity is based on its number of protons. Since protons are in the nucleus and chemical reactions do not involve the nucleus, the atom remains unchanged. However, there are some reactions that do involve changes in the nucleus. These are called nuclear reactions and do change one atom of an element into an atom of a different element.

1. Fill in the table below as a review. You will need your periodic table for this! Remember the atomic number (or # of protons) determines the element. If you have four protons and seven neutrons you have beryllium. The same is true if you have four protons and six neutrons...you still have beryllium.

Isotope

Total Protons 6

(Atomic #) 2

Total Neutrons 6

(Mass # - Atomic #) 12

Mass Number* 12

Total Electrons Outside Nucleus

Format for Nuclear Equation

K-40

19

21

40

19

Li-6

2

1

90

38

*NOTE: Do NOT use the atomic mass numbers from your periodic table.

Radioactivity is when a substance spontaneously emits radiation. Radioactive atoms (or radioisotopes) emit radiation because their nuclei are unstable. Unstable nuclei lose energy by emitting radiation in a spontaneous process called radioactive decay. Unstable radioactive atoms undergo radioactive decay until they form stable nonradioactive atoms. There are several types of radiation emitted during radioactive decay.

Types of Radiation: Alpha, Beta, and Gamma

Three types of radiation have been discovered. The types are called alpha, beta and gamma. Alpha rays turned out to be small particles of matter with a charge of +2 and a mass of 4 amu. It has been proved that an alpha particle contains two protons and two neutrons – it is identical to the nucleus of a helium atom. In fact, when an alpha particle slows down and gains two electrons it becomes a helium atom. The Greek letter alpha (α) is used to represent this particle but in equations to keep track of mass and protons we must use. Betas were also found to be particles; they are simply high-speed electrons. We use the Greek letter beta (β), but in equations it is used. When a beta slows down it becomes an electron. Gamma rays (γ) are not particles; they are high energy electromagnetic radiation. They are photons (light) with no charge or mass so we simply write in our equations.

In the above examples you should notice that the sum of the mass numbers on the left of the arrow equals the sum of the mass numbers on the right of the arrow and that the sum of the protons on the left equals the sum of the protons on the right.

2. Complete the following table.

Name

Charge

Mass

Greek Symbol

Equation Symbol

Identity

ALPHA

BETA

GAMMA

When an atom undergoes radioactive decay the product nucleus is often unstable and undergoes further decay. This occurs until a stable nucleus is produced. (There is no way for a student to know how an atom will decay. We will always tell you the mode of decay for equations.)

3. Write the nuclear equations for the following radioactive decay series. Use the periodic table.

Bombardment Reactions

So far, the equations we have written have involved natural radioactive decay and therefore natural transmutation (changing of one element into another element). However, we have learned to cause transmutation by bombardment of nuclei with high-energy particles. Bombardment allows us to prepare hundreds of isotopes that do not naturally exist, plus this is the method for the production of transuranium elements, all of the man-made elements that follow uranium on the periodic ta

12. Which type

Use the following chart to answer questions 13-16…

Radioactive Substance

Approximate half-life

Radon-222

4 days

Iodine-131

8 days

Radium-226

1600 years

Carbon-14

5730 years

Plutonium-239

24,120 years

Uranium-238

4,470,000,000