1. 25.2
Half-Life
C. Half-life (t1/2): time required for one-half of the nuclei of a radioisotope to decay to products radioactive atoms decay into atoms of a new element.

2. 25.2
Half-Life

3. 25.1

4. for Sample Problem 25.1

5. Transmutation Reactions
25.2
Transmutation Reactions
D. Transmutation: conversion of an atom of one element to an atom of another element.
1. can occur by radioactive decay can occur when particles bombard the nucleus of an atom elements in the periodic table with atomic numbers above 92 are the transuranium elements a. All transuranium elements undergo transmutation b. No transuranium element occurs in nature, & all are radioactive.

6. Transmutation Reactions
25.2
Transmutation Reactions
4. The first artificial transmutation reaction involved bombarding nitrogen gas with alpha particles.
The first artificial transmutation reaction involved bombarding nitrogen gas with alpha particles, as illustrated here. Interpreting Diagrams What particles were formed?

7. 1. Nuclear Fission: an atom splits a. power of nuclear power plants
25.3
Nuclear Fission
D. Nuclear Reactions
1. Nuclear Fission: an atom splits
a. power of nuclear power plants
In nuclear fission, a uranium-235 nucleus breaks into two smaller nuclei and releases neutrons. Predicting What happens when the released neutrons strike other uranium-235 nuclei?

8. 2. Fusion: nuclei combine to produce a nucleus of greater mass.
25.3
Nuclear Fusion
2. Fusion: nuclei combine to produce a nucleus of greater mass.
a. power of the stars

9. 25.2 Section Quiz.
1. If there were 128 grams of radioactive material initially, what mass remains after four half-lives?
4 grams
32 grams
16 grams
8 grams

10. 25.2 Section Quiz.
2. When transmutation occurs, the ________ always changes.
number of electrons
mass number
atomic number
number of neutrons

11. 25.2 Section Quiz
3. Transmutation occurs by radioactive decay and also by
extreme heating.
chemical reaction.
high intensity electrical discharge.
particle bombardment of the nucleus.