1. 5.2 Nuclear Reactions
In the nuclear equation for alpha decay, the mass number of the new nucleus decreases by 4 and its atomic number decreases by 2.
Learning Goal Write a balanced nuclear equation showing mass numbers and atomic numbers for radioactive decay.

2. Balancing Nuclear Equations
In a process called radioactive decay, the nucleus breaks down by emitting radiation. The process is represented by a nuclear in which
the mass number and atomic number may change.
the sum of the mass numbers and the sum of the atomic numbers are equal for the reactants and the products:
Mass number sum: =
251Cf  Cm He
Atomic number sum: =
Core Chemistry Skill Writing Nuclear Equations

3. Alpha Decay
Alpha decay occurs when a radioactive nucleus emits an alpha particle, forming a new nucleus with a mass number that is decreased by 4 and an atomic number that is decreased by 2.

4. Guide to Completing Nuclear Equations

5. Equation for Alpha Emission4 2 He
Complete the following nuclear equation for the decay of americium-241: STEP 1 Write the incomplete nuclear equation.
ANALYZE Given Need
THE PROBLEM Am-241, balanced nuclear equation
alpha decay

6. Equation for Alpha Emission4 2 He
Complete the following nuclear equation for the decay of americium-241: STEP 2 Determine the missing mass number. 241 = ? − 4 = ? 241 – 4 = 237 (mass number of new nucleus) STEP 3 Determine the missing atomic number. 95 = ? – 2 = ? 95 − 2 = 93 (atomic number of new nucleus)

7. Equation for Alpha Emission4 2 He
Complete the following nuclear equation for the decay of americium-241: STEP 4 Determine the symbol of the new nucleus. The element that has atomic number 93 is neptunium, Np. STEP 5 Complete the nuclear equation.

8. Beta Decay –1 e
In the nuclear equation for beta decay, a beta particle, an electron, is emitted from the nucleus when a neutron in the nucleus breaks down, forming a proton and a beta particle and increasing the atomic number by 1.

9. Equation for Beta Decay–1 e
Write an equation for the decay of 42K, a beta emitter. STEP 1 Write the incomplete nuclear equation.

10. Equation for Beta Decay–1 e
Write an equation for the decay of 42K, a beta emitter. STEP 2 Determine the missing mass number. 42 = ? – 0 = ? 42 − 0 = 42 (mass number of new nucleus) STEP 3 Determine the missing atomic number. 19 = ? − = ? = 20 (atomic number of new nucleus)

11. Equation for Beta Decay–1 e
Write an equation for the decay of 42K, a beta emitter. STEP 4 Determine the symbol of the new nucleus. The element that has atomic number 20 is calcium (Ca). STEP 5 Complete the nuclear equation.

12. Study Check
Write the nuclear equation for the beta decay of 60Co.

13. Solution
Write the nuclear equation for the beta decay of 60Co. STEP 1 Write the incomplete nuclear equation.

14. Solution
Write the nuclear equation for the beta decay of 60Co. STEP 2 Determine the missing mass number. 60 = ? – 0 = ? 60 − 0 = 60 (mass number of new nucleus) STEP 3 Determine the missing atomic number. 27 = ? − = ? = 28 (atomic number of new nucleus)

15. Solution
Write the nuclear equation for the beta decay of 60Co. STEP 4 Determine the symbol of the new nucleus. The element that has atomic number 28 is nickel (Ni). STEP 5 Complete the nuclear equation.

16. Positron Emission In positron emission,+1 e
In positron emission,
a proton is converted to a neutron and a positron.
the mass number of the new nucleus is the same, but the atomic number decreases by 1.

17. Gamma Radiation In gamma radiation,γ
In gamma radiation,
energy is emitted from an unstable nucleus, indicated by m following the mass number.
the mass number and the atomic number of the new nucleus are the same.

18. Summary of Types of Radiation
When the nuclei of alpha, beta, positron, and gamma emitters emit radiation, new and more stable nuclei are produced.

19. Producing Radioactive Isotopes
Radioactive isotopes are produced
when a stable nucleus is converted to a radioactive nucleus by bombarding it with a small particle.
in a process called transmutation.
When nonradioactive B-10 is bombarded by an alpha particle, the products are radioactive N-13 and a neutron.

20. Equation for Producing New Isotopes by Bombardment
Write the balanced nuclear equation for the bombardment of nickel-58 by a proton, , which produces a radioactive isotope and an alpha particle. STEP 1 Write the incomplete nuclear equation.

21. Equation for Producing New Isotopes by Bombardment
Write the balanced nuclear equation for the bombardment of nickel-58 by a proton, , which produces a radioactive isotope and an alpha particle. STEP 2 Determine the missing mass number = ? – 4 = ? 59 − 4 = 55 (mass number of new nucleus) STEP 3 Determine the missing atomic number = ? − 2 = ? 29 − 2 = 27 (atomic number of new nucleus)

22. Equation for Producing New Isotopes by Bombardment
Write the balanced nuclear equation for the bombardment of nickel-58 by a proton, , which produces a radioactive isotope and an alpha particle. STEP 4 Determine the symbol of the new nucleus. The element that has atomic number 27 is cobalt (Co). STEP 5 Complete the nuclear equation.

23. Study Check
What radioactive isotope is produced when a neutron bombards 98Tc, releasing an alpha particle?

24. Solution
What radioactive isotope is produced when a neutron bombards 98Tc, releasing an alpha particle? STEP 1 Write the incomplete nuclear equation.
ANALYZE Given Need
THE PROBLEM neutron bombardment balanced nuclear
Tc equation

25. Solution
What radioactive isotope is produced when a neutron bombards 98Tc, releasing an alpha particle? STEP 2 Determine the missing mass number = ? – 4 = ? 99 − 4 = 95 (mass number of new nucleus) STEP 3 Determine the missing atomic number = ? − 2 = ? 43 − 2 = 41 (atomic number of new nucleus)

26. Solution
What radioactive isotope is produced when a neutron bombards 98Tc, releasing an alpha particle? STEP 4 Determine the symbol of the new nucleus. The element that has atomic number 41 is niobium (Nb). STEP 5 Complete the nuclear equation.