2.2 Stable and unstable nuclei

• What are stable nuclei characterized by?

  No radioactive decay
• What are the two main factors affecting nuclear stability?

  Mass number and binding energy
• Match the type of decay with its emission:

  Alpha decay ↔️ Helium nucleus

  Beta decay ↔️ Electron or positron

  Gamma decay ↔️ High-energy photon
• Why do stable nuclei not undergo radioactive decay?

  Balanced proton-neutron ratio
• Stable nuclei have a high binding energy per nucleon


  True
• Unstable nuclei have a lower binding energy per nucleon compared to stable nuclei

  True
• What property of protons defines the atomic number of an element?

  Positive charge
• What is the binding energy per nucleon in stable nuclei?

  High
• The atomic number of an element is determined by the number of protons
• The time taken for half of the radioactive nuclei to decay is called half-life
• What is the difference between nuclear fusion and fission in terms of stability?

  Stable vs unstable products
• Unstable nuclei have a lower binding energy per nucleon
• Unstable nuclei decay to achieve a more stable configuration
• What property of stable nuclei prevents them from undergoing radioactive decay?

  High binding energy
• Neutrons help stabilize the nucleus by reducing proton repulsion


  True
• Isotopes of the same element have different mass
• What force governs the arrangement of protons and neutrons in the nucleus?

  Strong nuclear force
• The neutron-to-proton ratio affects nuclear stability


  True
• Where are protons and neutrons located in an atom?

  Nucleus
• Unstable nuclei undergo radioactive decay
• What happens to the proton-neutron ratio in unstable nuclei?

  Imbalanced
• What type of ratio do stable nuclei have between protons and neutrons?

  Balanced
• Unstable nuclei decay due to an imbalanced proton-neutron ratio
• Isotopes of the same element have the same number of protons
• What type of proton-neutron ratio do stable nuclei have?

  Balanced
• The total number of protons and neutrons in a nucleus is called the mass number.
• Isotopes have the same number of protons but different numbers of neutrons

  True
• Unstable nuclei decay to increase their binding energy per nucleon
• Lighter nuclei with balanced ratios of protons and neutrons are more stable
• Nuclear stability is influenced by both the mass number and the nuclear binding energy per nucleon
• Arrange the properties of stable and unstable nuclei based on their stability:

  1️⃣ Mass Number: Light nuclei with balanced ratios

  2️⃣ Nuclear Binding Energy per Nucleon: High

  3️⃣ Radioactive Decay: Do not undergo decay
• Stable nuclei have a balanced ratio of protons and neutrons
• Match the properties with the type of nuclei:

  Stable Nuclei ↔️ Balanced proton-neutron ratio

  Unstable Nuclei ↔️ Imbalanced proton-neutron ratio
• Isotopes of the same element have the same number of protons but different numbers of neutrons.


  True
• Stable nuclei have a balanced neutron-to-proton ratio
• There are three primary types of radioactive decay: alpha, beta, and gamma
• What type of particle is emitted in beta-plus decay?

  Positron
• In beta-plus decay, the atomic number decreases
• Steps in alpha decay

  1️⃣ An alpha particle is emitted

  2️⃣ Mass number decreases by 4

  3️⃣ Atomic number decreases by 2
• Match the type of decay with its particle emitted:

  Alpha Decay ↔️ Alpha particle

  Beta-minus Decay ↔️ Electron and antineutrino

  Beta-plus Decay ↔️ Positron and neutrino

  Gamma Decay ↔️ Gamma ray