Science Term 1 Year 9

Question 1

Define the term ‘isotope’.

Answer 1

An isotope is a variant of a chemical element that has the same number of protons (and thus the same atomic number) but a different number of neutrons, resulting in a different mass number.

Question 2

Identify the name of an isotope of barium with a mass number of 130.

Answer 2

The isotope of barium with a mass number of 130 is called Barium-130 (Ba-130).

Question 3

What is the name of an isotope of potassium with 22 neutrons?

Answer 3

The isotope is called Potassium-41 (K-41).

Potassium has an atomic number of 19, which means it has 19 protons. If it has 22 neutrons, its mass number would be 19 + 22 = 41.

Question 4

Name three important uses of radioisotopes.

Answer 4

1. Medical Imaging and Treatment: Used in diagnostic imaging (e.g., PET scans) and in cancer treatment (e.g., radiation therapy).
2. Industrial Applications: Used in non-destructive testing, gauging material thickness, and tracing leaks in pipelines.
3. Research: Used in biological and chemical research to trace the pathways of substances in biological systems.

Question 5

Define the electromagnetic spectrum.

Answer 5

The electromagnetic spectrum is the range of all types of electromagnetic radiation, which includes gamma rays, X-rays, ultraviolet light, visible light, infrared radiation, microwaves, and radio waves.

Question 6

Compare and contrast these isotopes of sodium: Na-23 and Na-24.

Answer 6

Na-23: Sodium-23 has 11 protons and 12 neutrons, making it stable and the most abundant isotope of sodium. Na-24: Sodium-24 has 11 protons and 13 neutrons, making it radioactive with a half-life of about 15 hours.

Comparison: Both isotopes have the same number of protons (11) and are forms of sodium, but they differ in their neutron count, mass number, stability, and radioactive properties.

Question 7

Outline the relationship between the mass of an isotope and its stability.

Answer 7

Generally, isotopes with a mass number that is too high or too low compared to the stable isotopes of an element tend to be unstable and radioactive. Stability is often associated with a balanced ratio of protons to neutrons.

Question 8

Summarise what happens to the nucleus of an element during alpha decay.

Answer 8

During alpha decay, the nucleus of an element emits an alpha particle, which consists of 2 protons and 2 neutrons. As a result, the atomic number of the element decreases by 2, and the mass number decreases by 4.

Question 9

List the main differences between stable isotopes and radioisotopes.

Answer 9

1. Stability: Stable isotopes do not undergo radioactive decay, while radioisotopes are unstable and decay over time.
2. Half-life: Stable isotopes have an infinite half-life, while radioisotopes have a finite half-life.
3. Applications: Stable isotopes are often used in non-destructive testing and tracing, while radioisotopes are used in medical treatments, imaging, and research.

Question 10

An element undergoes radioactive decay; its atomic number and mass number are not affected. Deduce the type of decay.

Answer 10

The type of decay is likely gamma decay. In gamma decay, the nucleus releases energy in the form of gamma radiation without changing its composition.

Question 11

During the radioactive decay of an isotope, a high-energy electron is released. Deduce the type of decay.

Answer 11

The type of decay is beta decay. In beta decay, a neutron in the nucleus is transformed into a proton, and a beta particle (which is a high-energy electron) is emitted.