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Organic Chemistry: Bonding and Structure Fundamentals

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  • What defines an organic molecule?
    An organic molecule contains both carbon and hydrogen. A molecule with only carbon and hydrogen is called a hydrocarbon.
  • What is the atomic number of an atom?
    The atomic number equals the number of protons in the nucleus.
  • How is the mass number of an atom calculated?
    Mass number = number of protons + number of neutrons.
  • What are isotopes?
    Atoms with the same atomic number but different numbers of neutrons.
  • What is an atomic orbital?
    A region of space around the nucleus where there is a high probability of finding an electron.
  • What is an electron shell and subshell?
    A shell is a group of orbitals with the same principal quantum number; a subshell is a region 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).
  • State the Aufbau Principle.
    Electrons fill atomic orbitals in order of increasing energy, starting from the lowest energy orbital.
  • What does the Pauli Exclusion Principle state?
    Each atomic orbital can hold a maximum of two electrons with opposite spins.
  • Explain Hund's Rule.
    Electrons fill degenerate orbitals singly with parallel spins before pairing up.
  • What is the Heisenberg Uncertainty Principle?
    It is impossible to simultaneously know both the exact position and momentum of an electron.
  • What is a wave function in quantum mechanics?
    A mathematical function that describes the energy state and probability distribution of an electron.
  • What is a molecular orbital?
    A region formed by the constructive or destructive overlap of atomic orbitals where electrons are shared between atoms.
  • Define sigma (σ) and pi (π) bonds.
    A σ-bond is formed by head-on overlap of orbitals; a π-bond is formed 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, resembling a noble gas configuration.
  • How do first-row elements like H, He, and Li differ in octet rule satisfaction?
    They prefer to have fewer than 8 electrons: H and He prefer 2 electrons, Li often has 1 electron.
  • What are formal charges?
    Formal charge = Group number - (number of lone electrons + 1/2 number of bonding electrons). It helps determine the most stable Lewis structure.
  • What is the bondline (skeletal) structure convention?
    Carbons are implied at line ends and vertices; hydrogens on carbons are implied to fill octets; heteroatoms and hydrogens on them are drawn explicitly.
  • What are bonding preferences of second-row elements?
    Determined by group number: C prefers 4 bonds, N prefers 3 bonds and 1 lone pair, O prefers 2 bonds and 2 lone pairs, F prefers 1 bond and 3 lone pairs.
  • How does molecular orbital theory explain bond stability?
    Constructive overlap forms bonding orbitals that lower energy and stabilize molecules; destructive overlap forms antibonding orbitals that raise energy.