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Gen Chem (13)
| Question | Answer |
|---|---|
| What is the nucleus composed of, and what are these particles collectively called? | The nucleus is composed of protons and neutrons, collectively called nucleons. Protons carry a positive charge; neutrons are neutral. |
| What are isotopes? | Isotopes are atoms of the same element (same number of protons) that differ in the number of neutrons. The number of protons determines the element. |
| What is the isotope notation, and how do you calculate the number of neutrons? | Mass number (A) = protons + neutrons; Atomic number (Z) = protons. Number of neutrons = A − Z. |
| What is mass defect? | Mass defect is the difference between the calculated mass of a nucleus (sum of individual nucleons) and its actual measured mass. The "missing" mass is converted into binding energy when the nucleus forms. |
| What is binding energy? | Binding energy is the energy required to break a nucleus into individual nucleons, or equivalently the energy released when the nucleus forms. |
| What does a greater mass defect indicate? | A greater mass defect indicates greater binding energy, since E and Δm are directly proportional |
| What is nuclear fission? | Nuclear fission occurs when a very heavy nucleus collides with a neutron and splits into two smaller atoms, releasing neutrons and energy. Both mass number and proton number are conserved. |
| What is nuclear fusion? | Nuclear fusion occurs when two or more lighter nuclei fuse into one larger nucleus, releasing energy. The most famous example is the sun, where 4 hydrogen atoms fuse into 1 helium atom. Both mass number and proton number are conserved. |
| What is radioactive decay? | Radioactive decay occurs when the nucleus of an unstable element spontaneously decays into a more stable element and releases a radioactive particle. |
| What is alpha (α) decay? What changes in mass number (A) and atomic number (Z)? | Alpha decay releases an alpha particle (⁴₂He), composed of 2 protons and 2 neutrons. A decreases by 4; Z decreases by 2. It typically occurs in heavier atoms to reduce mass. |
| What is beta plus (β⁺) / positron decay? What changes in A and Z? | A positron (β⁺) is released. A proton is converted to a neutron, so A is unchanged and Z decreases by 1. |
| What is beta minus (β⁻) decay? What changes in A and Z? | An electron (β⁻) is released. A neutron is converted to a proton, so A is unchanged and Z increases by 1. |
| What is electron capture? What changes in A and Z? | The nucleus captures an inner-shell electron, combining it with a proton to form a neutron. A is unchanged; Z decreases by 1. It is a special type of beta decay. |
| What is gamma (γ) decay? What changes in A and Z? | An excited, high-energy nucleus releases excess energy as high-frequency gamma rays to reach a stable, lower-energy state. Neither A nor Z changes. An asterisk () denotes the high-energy state: ᴬ𝓩X → ᴬ𝓩X + γ. |
| Rank the penetrating power of alpha, beta, and gamma radiation from least to greatest. | Alpha (least penetrating — blocked by paper) < Beta (blocked by thin wood/aluminum) < Gamma (most penetrating — requires lead or thick metal). Smaller particles penetrate more. |
| What is radioactive half-life? | Radioactive half-life is the time it takes for half of the original amount of a parent isotope to decay into its daughter isotope. All decay follows first-order kinetics, so the half-life is constant regardless of how much sample remains. |
| Summary — which decay types change A, and which change Z? | Alpha: A −4, Z −2. Beta plus: A unchanged, Z −1. Beta minus: A unchanged, Z +1. Electron capture: A unchanged, Z −1. Gamma: A unchanged, Z unchanged. |
Created by:
smurtab