7.1 Atomic Physics

1. The number of nucleons in a nucleus is the number of

Particles in the nucleus.

Neutrons in the nucleus.

Protons in the nucleus.

Protons plus neutrons in the nucleus.

The number of nucleons in a nucleus refers to the total number of particles present in the nucleus. Nucleons include both protons and neutrons, so the correct answer is protons plus neutrons in the nucleus. This is because protons and neutrons are the two types of particles found in the nucleus, and their combined count gives the total number of nucleons.

Explanation

The number of nucleons in a nucleus refers to the total number of particles present in the nucleus. Nucleons include both protons and neutrons, so the correct answer is protons plus neutrons in the nucleus. This is because protons and neutrons are the two types of particles found in the nucleus, and their combined count gives the total number of nucleons.

2. Ag-102, Ag-103 and Ag-104 are three isotopes of the element silver. Which one of the following is a true statement about the nuclei of these isotopes?

All have the same mass.

All have the same number of nucleons.

All have the same number of neutrons.

All have the same number of protons.

The statement "All have the same number of protons" is true because isotopes of an element have the same number of protons, which determines the element's identity. The difference between isotopes lies in the number of neutrons, which can vary. Therefore, Ag-102, Ag-103, and Ag-104 all have the same number of protons, but different numbers of neutrons, resulting in different atomic masses.

Explanation

The statement "All have the same number of protons" is true because isotopes of an element have the same number of protons, which determines the element's identity. The difference between isotopes lies in the number of neutrons, which can vary. Therefore, Ag-102, Ag-103, and Ag-104 all have the same number of protons, but different numbers of neutrons, resulting in different atomic masses.

3. The Geiger-Marsden alpha particle scattering experiment provides evidence for the existence of

Atomic nuclei.

Neutrons.

Protons.

Nuclear energy levels.

The Geiger-Marsden alpha particle scattering experiment involved firing alpha particles at a thin sheet of gold foil. According to the plum pudding model of the atom, the positive charge in an atom was thought to be spread out evenly throughout the atom. However, the experiment showed that some alpha particles were deflected at large angles or even bounced back, which indicated the presence of a dense, positively charged center in the atom. This center was later identified as the atomic nucleus, providing evidence for the existence of atomic nuclei.

Explanation

The Geiger-Marsden alpha particle scattering experiment involved firing alpha particles at a thin sheet of gold foil. According to the plum pudding model of the atom, the positive charge in an atom was thought to be spread out evenly throughout the atom. However, the experiment showed that some alpha particles were deflected at large angles or even bounced back, which indicated the presence of a dense, positively charged center in the atom. This center was later identified as the atomic nucleus, providing evidence for the existence of atomic nuclei.

4. The existence of isotopes provides evidence for the presence of

Electrons in atomic energy levels.

Electrons in the nuclei of atoms.

Neutrons in the nuclei of atoms.

Protons in the nuclei of atoms.

Isotopes are atoms of the same element that have the same number of protons but different numbers of neutrons. The fact that isotopes exist and have different masses provides evidence for the presence of neutrons in the nuclei of atoms. If all atoms had the same number of protons and electrons, there would be no variation in atomic mass. Therefore, the existence of isotopes supports the idea that there are particles other than protons and electrons in the nucleus, which are the neutrons.

Explanation

Isotopes are atoms of the same element that have the same number of protons but different numbers of neutrons. The fact that isotopes exist and have different masses provides evidence for the presence of neutrons in the nuclei of atoms. If all atoms had the same number of protons and electrons, there would be no variation in atomic mass. Therefore, the existence of isotopes supports the idea that there are particles other than protons and electrons in the nucleus, which are the neutrons.

5. Which of the following identifies the significant interaction(s) between nucleons inside the nucleus?

Nuclear only

Coulomb only

Weak Nuclear and Coulomb

Gravitational, nuclear and Coulomb

Strong Nuclear and Coulomb

The strong nuclear force and the Coulomb force are the two significant interactions between nucleons inside the nucleus. The strong nuclear force is responsible for holding the nucleus together by overcoming the electrostatic repulsion between protons. It is a short-range force that acts only within the nucleus. The Coulomb force, on the other hand, is the electrostatic force of attraction or repulsion between charged particles. It acts between protons and between protons and neutrons in the nucleus. Both of these forces play a crucial role in determining the stability and properties of the nucleus.

Explanation

The strong nuclear force and the Coulomb force are the two significant interactions between nucleons inside the nucleus. The strong nuclear force is responsible for holding the nucleus together by overcoming the electrostatic repulsion between protons. It is a short-range force that acts only within the nucleus. The Coulomb force, on the other hand, is the electrostatic force of attraction or repulsion between charged particles. It acts between protons and between protons and neutrons in the nucleus. Both of these forces play a crucial role in determining the stability and properties of the nucleus.

6. The atomic line spectra of elements provides evidence for the existence of

Protons

Electrons

Neutrons

Quantized energy states within nuclei

Quantized energy states within atoms

The correct answer is quantized energy states within atoms. The atomic line spectra of elements refers to the specific wavelengths of light emitted or absorbed by atoms when they transition between different energy levels. This phenomenon can only be explained if the energy levels within atoms are quantized, meaning they can only have specific discrete values. This supports the concept of quantized energy states within atoms. The other options, such as protons, electrons, neutrons, and quantized energy states within nuclei, are not directly related to the atomic line spectra.

Explanation

The correct answer is quantized energy states within atoms. The atomic line spectra of elements refers to the specific wavelengths of light emitted or absorbed by atoms when they transition between different energy levels. This phenomenon can only be explained if the energy levels within atoms are quantized, meaning they can only have specific discrete values. This supports the concept of quantized energy states within atoms. The other options, such as protons, electrons, neutrons, and quantized energy states within nuclei, are not directly related to the atomic line spectra.

7. In the Geiger Marsden experiment, alpha particles are scattered by gold nuclei. The experimental results indicate that most alpha particles are:

Scattered only at small angles

Scattered only at large angles

Absorbed in the target

Scattered back along the original direction

The correct answer is scattered only at small angles. This is because the Geiger Marsden experiment showed that most alpha particles passed through the gold foil without being deflected, indicating that they did not interact with the gold nuclei. However, a small fraction of the alpha particles were scattered at small angles, suggesting that they experienced a close encounter with the gold nuclei and were deflected slightly.

Explanation

The correct answer is scattered only at small angles. This is because the Geiger Marsden experiment showed that most alpha particles passed through the gold foil without being deflected, indicating that they did not interact with the gold nuclei. However, a small fraction of the alpha particles were scattered at small angles, suggesting that they experienced a close encounter with the gold nuclei and were deflected slightly.

8. Which of the following provides evidence for the existence of atomic energy levels?

Alpha-particle scattering

Continuous emission spectra

Discrete energies of gamma radiation

Line absorption spectra

Line absorption spectra provide evidence for the existence of atomic energy levels. When atoms absorb light, they do so at specific wavelengths corresponding to the energy differences between different energy levels within the atom. This results in dark lines or gaps in the continuous spectrum, known as absorption lines. These absorption lines provide direct evidence for the existence of discrete energy levels within atoms, confirming the theory of atomic energy levels.

Explanation

Line absorption spectra provide evidence for the existence of atomic energy levels. When atoms absorb light, they do so at specific wavelengths corresponding to the energy differences between different energy levels within the atom. This results in dark lines or gaps in the continuous spectrum, known as absorption lines. These absorption lines provide direct evidence for the existence of discrete energy levels within atoms, confirming the theory of atomic energy levels.