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Atomic Structure definitions

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  • Atom
    Basic unit of matter, composed of a nucleus containing protons and neutrons, with electrons in surrounding orbits.
  • Nucleus
    Dense central region of an atom, containing protons and neutrons, and accounting for most of the atom's mass.
  • Proton
    Positively charged subatomic particle found in the nucleus, determining the atomic number and identity of an element.
  • Neutron
    Neutral subatomic particle located in the nucleus, contributing to atomic mass but not to charge.
  • Electron
    Negatively charged subatomic particle found in regions around the nucleus, influencing chemical behavior and charge.
  • Atomic Number
    Value equal to the number of protons in an atom, unique for each element and used to identify it.
  • Mass Number
    Sum of protons and neutrons in an atom's nucleus, representing the total count of these subatomic particles.
  • Isotope
    Form of an element with the same number of protons but a different number of neutrons, resulting in varying mass numbers.
  • Shell
    Region around the nucleus defined by a specific energy level where electrons are likely to be found.
  • Orbital
    Subregion within a shell that can hold a maximum of two electrons with opposite spins.
  • Ion
    Atom with unequal numbers of protons and electrons, resulting in a net positive or negative charge.
  • Cation
    Positively charged ion formed when an atom has more protons than electrons.
  • Anion
    Negatively charged ion formed when an atom has more electrons than protons.
  • Aufbau Principle
    Rule stating that electrons fill the lowest energy orbitals first before occupying higher energy ones.
  • Pauli Exclusion Principle
    Rule stating that a maximum of two electrons, with opposite spins, can occupy the same orbital.
  • Hund's Rule
    Rule stating that electrons fill all orbitals of equal energy singly before any orbital is doubly occupied.