G12 T3 Classwork 1

1. A radioactive nucleus contains 138 neutrons. The nucleus emits an α-particle.How many neutrons are in the nucleus after it has emitted the α-particle?

When a nucleus emits an α-particle, it loses two protons and two neutrons. Since the question only asks about the number of neutrons, we can ignore the protons. Therefore, the number of neutrons in the nucleus after it has emitted the α-particle would be 138 - 2 = 136.

Explanation

When a nucleus emits an α-particle, it loses two protons and two neutrons. Since the question only asks about the number of neutrons, we can ignore the protons. Therefore, the number of neutrons in the nucleus after it has emitted the α-particle would be 138 - 2 = 136.

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3. A powder contains 400mg of a radioactive material that emits α-particles.The half-life of the material is 5 days. What mass of that material remains after 10 days?

The half-life of a radioactive material is the time it takes for half of the material to decay. In this case, the half-life is 5 days. After 5 days, half of the material will have decayed, leaving 200mg remaining. After another 5 days (10 days total), another half of the remaining material will have decayed, leaving 100mg remaining. Therefore, the mass of the material that remains after 10 days is 100mg.

Explanation

The half-life of a radioactive material is the time it takes for half of the material to decay. In this case, the half-life is 5 days. After 5 days, half of the material will have decayed, leaving 200mg remaining. After another 5 days (10 days total), another half of the remaining material will have decayed, leaving 100mg remaining. Therefore, the mass of the material that remains after 10 days is 100mg.

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4. How many electrons are in a nucleus of

if the atom is neutral?

The number of electrons in an atom's nucleus is always zero. Electrons are negatively charged particles that orbit the nucleus in specific energy levels. The nucleus, on the other hand, contains positively charged protons and usually neutral neutrons. Therefore, the statement that there are 19 electrons in the nucleus is incorrect.

Explanation

The number of electrons in an atom's nucleus is always zero. Electrons are negatively charged particles that orbit the nucleus in specific energy levels. The nucleus, on the other hand, contains positively charged protons and usually neutral neutrons. Therefore, the statement that there are 19 electrons in the nucleus is incorrect.

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5. A radioactive nucleus contains 138 nucleons. The nucleus emits an α-particle.How many nucleons are in the nucleus after it has emitted the α-particle?

When a radioactive nucleus emits an α-particle, it loses 2 protons and 2 neutrons. Since the nucleus initially contains 138 nucleons, after emitting the α-particle, it will have 136 nucleons remaining. Therefore, the correct answer is 134 nucleons.

Explanation

When a radioactive nucleus emits an α-particle, it loses 2 protons and 2 neutrons. Since the nucleus initially contains 138 nucleons, after emitting the α-particle, it will have 136 nucleons remaining. Therefore, the correct answer is 134 nucleons.

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6. An atom of the element lithium has a nucleon number of 7 and a proton number of 3.Which diagram represents a neutral atom of lithium?

Diagram A

Diagram B

Diagram C

Diagram D

Diagram C represents a neutral atom of lithium because it shows 3 protons in the nucleus, which is consistent with the proton number of 3 for lithium. It also shows 4 neutrons in the nucleus, which gives a total nucleon number of 7, as stated in the question. The diagram also shows 3 electrons orbiting the nucleus, which balances out the positive charge of the protons, making the atom neutral.

Explanation

Diagram C represents a neutral atom of lithium because it shows 3 protons in the nucleus, which is consistent with the proton number of 3 for lithium. It also shows 4 neutrons in the nucleus, which gives a total nucleon number of 7, as stated in the question. The diagram also shows 3 electrons orbiting the nucleus, which balances out the positive charge of the protons, making the atom neutral.

7. The diagram shows the paths of three different types of radiation, X, Y and Z.

A

B

C

D

The explanation for the correct answer B is not available.

Explanation

The explanation for the correct answer B is not available.

8. Order the decay types in order of ionization power.

Highest

Medium

Lowest

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9. What is a β-particle and from which part of a radioactive atom is it emitted?

Electron from the nucleus

Electron from outer orbits

Helium nucleus from the nucleus

Helium nucleus from outer orbits

A β-particle is an electron that is emitted from the nucleus of a radioactive atom. It is not emitted from the outer orbits of the atom.

Explanation

A β-particle is an electron that is emitted from the nucleus of a radioactive atom. It is not emitted from the outer orbits of the atom.

10. Which type of radiation has the greatest ionising effect?

α-particles

β-particles

γ-rays

All have the same ionising effect

Alpha particles have the greatest ionizing effect among the given options. This is because alpha particles are large and heavy, consisting of two protons and two neutrons. They have a positive charge and high kinetic energy, allowing them to collide with atoms and remove electrons, causing ionization. Beta particles, on the other hand, are smaller and lighter, consisting of high-energy electrons or positrons. Gamma rays are electromagnetic waves with no mass or charge. While all types of radiation can cause ionization, alpha particles are more effective due to their size and charge.

Explanation

Alpha particles have the greatest ionizing effect among the given options. This is because alpha particles are large and heavy, consisting of two protons and two neutrons. They have a positive charge and high kinetic energy, allowing them to collide with atoms and remove electrons, causing ionization. Beta particles, on the other hand, are smaller and lighter, consisting of high-energy electrons or positrons. Gamma rays are electromagnetic waves with no mass or charge. While all types of radiation can cause ionization, alpha particles are more effective due to their size and charge.