Fisika kelas 12 | Fisika Inti dan Radioaktivitas

Summary

This video introduces the topic of nuclear physics and radioactivity, focusing on the structure of atomic nuclei and the particles that make them up. It covers the key components of an atom—protons, neutrons, and electrons—and explains isotopes, isotones, and isobars. The video also delves into the concept of mass defect and binding energy, discussing the stability of atomic nuclei and the process of radioactive decay. The three main types of radioactive emissions—alpha particles, beta particles, and gamma rays—are explained, alongside the mathematical formulas for calculating decay rates and energy released during nuclear reactions.

Takeaways

• 😀 The atomic nucleus is made up of protons and neutrons, while electrons are found in the outer shell of the atom.
• 😀 The mass of a proton is 1.67 x 10^-27 kg, while a neutron has a mass of 1.675 x 10^-27 kg, and an electron has a mass of 9.11 x 10^-31 kg.
• 😀 Atomic symbols are written with 'X' representing the element, 'Z' for the atomic number, and 'A' for the mass number.
• 😀 Isotopes are atoms of the same element with the same number of protons but different numbers of neutrons (e.g., oxygen-16, oxygen-17, and oxygen-18).
• 😀 Isobars are atoms with the same mass number but different atomic numbers (e.g., hydrogen-3 and helium-4).
• 😀 The unit for atomic mass is the atomic mass unit (AMU), where 1 AMU = 1/12 of the mass of a carbon-12 atom.
• 😀 The difference between the total mass of protons and neutrons and the actual mass of the nucleus is known as mass defect, which is converted into binding energy.
• 😀 Radioactive decay occurs when an unstable nucleus emits alpha, beta, or gamma radiation to reach stability.
• 😀 Alpha particles consist of two protons and two neutrons and have high ionizing power but low penetrating ability.
• 😀 Beta particles are electrons emitted when a neutron transforms into a proton. They have moderate ionizing and penetrating power.
• 😀 Gamma radiation consists of high-energy electromagnetic waves with the highest penetrating power but low ionizing power.
• 😀 Half-life (t1/2) is the time it takes for half of a radioactive substance to decay, and it can be calculated using the equation t1/2 = 0.693 / λ.
• 😀 The energy released in nuclear reactions (fusion or fission) can be calculated using mass-energy equivalence (E = Δm * 931.5 MeV).
• 😀 The decay constant (λ) and half-life (t1/2) are related, and the remaining amount of a radioactive substance can be calculated using the formula N = N0 * (1/2)^(t/t1/2).

Q & A

What are the three main particles that make up an atom?

An atom consists of three main particles: electrons, protons, and neutrons. Electrons have a negative charge, protons have a positive charge, and neutrons are neutral.

What is the significance of the mass of protons and neutrons in an atom?

The mass of protons and neutrons is concentrated in the nucleus of the atom. Protons have a mass of approximately 1.67 x 10^-27 kg, and neutrons have a similar mass of 1.675 x 10^-27 kg, much heavier than electrons, which have a mass of 9.11 x 10^-31 kg.

What does the atomic symbol X represent?

In the atomic symbol X, 'X' represents the chemical element. The number 'Z' below X indicates the atomic number (the number of protons), and the number 'A' above X represents the mass number, which is the sum of protons and neutrons.

What is the difference between isotopes and isobars?

Isotopes are atoms of the same element that have the same number of protons but different numbers of neutrons, resulting in different mass numbers. Isobars, on the other hand, are atoms with different elements but the same mass number.

What is mass defect in atomic physics?

Mass defect refers to the difference between the total mass of an atom's protons and neutrons and the actual mass of the atomic nucleus. This difference is converted into binding energy, which holds the nucleus together.

How is the energy released during radioactive decay calculated?

The energy released during radioactive decay is calculated using the formula E = Δm x 931.5 MeV, where Δm is the mass defect (the difference between the mass of the atom and the sum of its individual protons and neutrons).

What are alpha particles, and how do they affect an atom?

Alpha particles consist of two protons and two neutrons, essentially making them helium nuclei. When emitted, alpha particles cause a reduction in the atom’s mass number by 4 and its atomic number by 2.

How do beta particles differ from alpha particles in terms of penetration ability?

Beta particles, which are high-energy electrons, have greater penetration ability compared to alpha particles, which have low penetration power. However, alpha particles have much higher ionizing power.

What is gamma radiation and how does it compare to alpha and beta radiation?

Gamma radiation consists of high-energy electromagnetic waves (photons) and has no mass or charge. It has the highest penetrating power compared to alpha and beta radiation, but its ionizing power is the lowest.

What is the concept of half-life in radioactive decay?

Half-life is the time required for half of a sample of a radioactive substance to decay. It is given by the equation T_half = 0.693 / λ, where λ is the decay constant.

How is the energy released in a fusion reaction calculated?

The energy released in a fusion reaction is calculated by comparing the mass of the reactants and products. The mass defect (difference in mass) is converted to energy using the formula E = Δm x 931.5 MeV.