The correct answer is Isotopes have the same atomic number but differ in their number of neutrons, which affects physical properties like mass.. Explanation & Key Takeaways: • Isotopes: Isotopes are variants of a particular chemical element that have the same number of protons (and hence the same atomic number) but a different number of neutrons, which affects their atomic mass. • Chemical Properties: The chemical properties of an atom are primarily determined by its electron configuration, which is dictated by the atomic number (number of protons). Since isotopes of an element have the same atomic number, their chemical properties are identical. • Physical Properties: Physical properties, such as density, melting point, and boiling point, can vary between isotopes because these properties are influenced by the mass of the atom. The differing number of neutrons causes a difference in atomic mass. • Example: Hydrogen has three isotopes: protium (1 proton, 0 neutrons), deuterium (1 proton, 1 neutron), and tritium (1 proton, 2 neutrons). While their chemical properties are the same, their physical properties, like mass, differ significantly. • Correct Statement: The statement that isotopes have the same atomic number but differ in their number of neutrons, which affects physical properties like mass, is accurate. This is why isotopes exhibit identical chemical behavior but different physical characteristics. Related Concepts: • Definition of Isotopes: Isotopes are atoms of the same element that have the same number of protons but a different number of neutrons. This difference in neutrons leads to variations in atomic mass. • Applications of Isotopes: • Carbon Dating: The isotope Carbon-14 is used to determine the age of archaeological specimens through radiocarbon dating. • Medical Imaging: Isotopes like Technetium-99m are widely used in medical imaging techniques like SPECT scans. • Nuclear Energy: Uranium isotopes, such as Uranium-235, are used as fuel in nuclear reactors. • Industrial Applications: Isotopes like Cobalt-60 are used for sterilization and radiation therapy. • Key Characteristics of Isotopes: • Stability: Some isotopes are stable, while others are radioactive and decay over time. • Mass Number: The mass number of an isotope is the sum of protons and neutrons in its nucleus. • Physical Differences: Isotopes can exhibit differences in physical properties, such as: • Density: Heavier isotopes of an element are denser. • Boiling and Melting Points: These can vary slightly based on mass differences. • Examples of Isotopes: • Chlorine: Exists as Chlorine-35 and Chlorine-37. • Oxygen: Has isotopes like Oxygen-16, Oxygen-17, and Oxygen-18. Important Notes: • Misconceptions Addressed: • Statement 2: Incorrect as isotopes have the same atomic structure except for the number of neutrons. • Statement 3: Incorrect because isotopes do not differ in the number of protons; they differ in neutrons. • Statement 4: Incorrect as isotopes have the same number of protons but differ in neutrons, not electrons. • Relevance in Science: Understanding isotopes is crucial for fields like nuclear physics, chemistry, biology, and archaeology. • Periodic Table: Isotopes do not change the placement of elements in the periodic table since placement is based on the atomic number (protons).