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  • What defines an organic molecule?_updated

    An organic molecule contains both carbon and hydrogen. A molecule with only carbon and hydrogen is called a hydrocarbon.
  • How is the mass number of an atom calculated?
    Mass number = number of protons + number of neutrons.
  • What is the atomic number of an atom?
    The atomic number equals the number of protons in the nucleus.
  • What are isotopes?
    Atoms with the same atomic number but different numbers of neutrons.
  • What is an atomic orbital?
    A region of space within a shell that can hold a pair of electrons with opposite spins.
  • What are cations and anions?
    Cations are positively charged atoms (fewer electrons than protons). Anions are negatively charged atoms (more electrons than protons).
  • What does the Aufbau Principle state?
    Electrons fill orbitals in order of increasing energy.
  • What is the Pauli Exclusion Principle?
    An orbital can hold a maximum of two electrons with opposite spins.
  • What does Hund's Rule state?
    Electrons fill orbitals of equal energy singly before pairing up.
  • What is the Heisenberg Uncertainty Principle?
    It is impossible to simultaneously know an electron's exact position and momentum.
  • What is a wave function in quantum mechanics?
    A mathematical equation describing the energy state of an electron; its square gives the probability of finding the electron.
  • What is an atomic orbital shape?
    A 3D plot of the wave function showing regions where the probability of finding an electron is high.
  • What happens when atomic orbitals overlap constructively?
    They form bonding molecular orbitals with increased electron density between nuclei.
  • What is the Linear Combination of Atomic Orbitals (LCAO)?
    A method to mathematically combine atomic orbitals by addition or subtraction to form molecular orbitals.
  • What are sigma (σ) and pi (π) bonds?
    σ-bonds form by head-on overlap of orbitals; π-bonds form by side-on overlap of p orbitals.
  • What is the octet rule?
    Atoms tend to gain, lose, or share electrons to achieve a full valence shell of 8 electrons, like noble gases.
  • How many octet electrons do first-row elements like H, He, and Li prefer?
    They prefer to have 2 octet electrons.

  • What are formal charges? tet

    Formal charge = Group number - (number of valence electrons + number of bonds). It helps determine the most stable Lewis structure.
  • What is a skeletal (bondline) structure?
    A simplified organic structure where carbons are implied at line ends and hydrogens on carbons are usually omitted.
  • When must hydrogens be drawn explicitly in skeletal structures?
    Hydrogens attached to heteroatoms (non-carbons) must always be drawn explicitly.