Radioactive Substances Quiz Questions

The number given in the question, 30, represents the number of neutrons in the nuclide.

The half-life of a radioactive sample is the time it takes for half of the atoms to decay. In this case, the half-life is 4 days. After 4 days, half of the 8000 undecayed atoms will decay, leaving 4000 undecayed atoms. After another 4 days (8 days total), half of the remaining 4000 undecayed atoms will decay, leaving 2000 undecayed atoms. Finally, after 12 days (3 half-lives), half of the remaining 2000 undecayed atoms will decay, leaving 1000 undecayed atoms.

The nucleus contains most of the mass of an atom. It is located at the center of the atom and is made up of protons and neutrons. The protons have a positive charge, while the neutrons have no charge. The electrons, which have a negative charge, are located in shells or orbits around the nucleus. However, the mass of electrons is significantly smaller compared to the mass of protons and neutrons, which is why the nucleus contains most of the mass of an atom.

The background count rate can be determined by observing the graph. As the material decayed to a very low level, the detector still recorded a count rate of 20. This indicates that even when there is no radioactive material present, the detector still detects a background radiation count rate of 20.

Option B is the correct way to represent the nucleus of this particular form of carbon. The atomic number of an element represents the number of protons in its nucleus, and in this case, carbon has 6 protons. The mass number represents the total number of protons and neutrons in the nucleus, and in this case, carbon has 6 protons and 7 neutrons. Therefore, the correct representation is 6 protons and 7 neutrons, which is shown in option B.

The symbol A could represent an alpha particle. Alpha particles are made up of two protons and two neutrons, which gives them a charge of +2. The symbol A is commonly used to represent the atomic mass number, which is the total number of protons and neutrons in an atom. Therefore, A is a suitable symbol to represent an alpha particle.

The initial count rate is equal to the sum of the background count rate and the count rate due to the radioactive substance. Since the detector still recorded background radiation when the material had decayed to a very low level, we can assume that the background count rate is 0. Therefore, the initial count rate is equal to the count rate due to the radioactive substance, which is 100.

The symbol "B" represents a beta particle.

The given information states that the nuclide of iron has 26 electrons, which is equal to the atomic number of iron. The atomic number represents the number of protons in an atom. Therefore, the correct answer is 26 protons.

The half-life of a radioactive substance is the time it takes for half of the substance to decay. In this case, the graph shows that the substance decays completely in 8 days. Therefore, the half-life of the substance is also 8 days.

The alpha particle is back-scattered because it is repelled by the nucleus when it passes by very near. As the alpha particle approaches the gold nucleus, it experiences a strong electrostatic repulsion due to the positive charge of the nucleus. This repulsion causes the alpha particle to change direction and be scattered backwards. The closer the alpha particle gets to the nucleus, the stronger the repulsion and the greater the scattering angle.

The alpha particle (2) was undeflected as it passed the gold nucleus because it had like charges with the nucleus, but it was far away from it. Like charges repel each other, so if the alpha particle had been closer to the nucleus, it would have been deflected. However, since it was far away, the repulsive force between the like charges was not strong enough to cause any deflection.