Question

1. what is meant by half - life? give an example of how half - life is useful in science. 7. complete the missing information for these isotopes: (look at the board) 8. which statement best explains why some isotopes are radioactive? a. they have too many or too few neutrons compared to protons.

Explanation:

1. The half - life is the time it takes for half of the atoms of a radioactive substance to decay. For example, in carbon - dating, the half - life of carbon - 14 (5730 years) is used to determine the age of organic materials. Scientists measure the ratio of carbon - 14 to stable carbon isotopes in a sample, and based on the known half - life, they can calculate how long ago the organism died.
2. Without seeing the board, in general, isotopes have the same number of protons but different numbers of neutrons. Information such as atomic number (number of protons), mass number (sum of protons and neutrons), and the number of neutrons can be used to complete details about isotopes. For example, if you know the atomic number of an element and the mass number of an isotope of that element, you can find the number of neutrons by subtracting the atomic number from the mass number.
3. Isotopes are radioactive when they have an unstable nucleus. This instability often occurs when there are too many or too few neutrons compared to protons. The imbalance causes the nucleus to decay over time, emitting radiation in the form of alpha, beta, or gamma particles. Option A provides a reason related to the neutron - proton ratio which is a common cause of radioactivity in isotopes.

Answer:

1. The half - life is the time required for half of the atoms of a radioactive substance to decay. Example: Carbon - dating uses the 5730 - year half - life of carbon - 14 to determine the age of organic materials.
2. Use atomic number, mass number and the relationship between protons and neutrons to complete isotope information.
3. A. They have too many or too few neutrons compared to protons.