Electron affinity is the energy change that occurs when an electron is added to a neutral atom in the gaseous state, indicating how strongly an atom can attract additional electrons. It generally becomes more exothermic across a period due to increasing nuclear charge and less exothermic down a group due to increased atomic radius and electron shielding.
Quantum mechanics is a fundamental theory in physics that describes the physical properties of nature at the smallest scales, such as atoms and subatomic particles. It introduces concepts like wave-particle duality, uncertainty principle, and quantum entanglement, which challenge classical intuitions about the behavior of matter and energy.
Large atoms, characterized by their high atomic numbers, exhibit complex electron configurations and are pivotal in the study of quantum mechanics and nuclear chemistry. Their size and the shielding effect of inner electrons lead to unique chemical properties and are essential in understanding the behavior of elements in the periodic table.