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General Chemistry: Atomic Structure and Bonding Concepts

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  • What defines the atomic number of an atom?
    The atomic number is equal to 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 a subshell?
    A shell is a region of space where electrons orbit; a subshell is a region within a shell that can hold a pair of electrons with opposite spins.
  • What are ions?
    Atoms with a different number of electrons than protons; cations are positively charged, anions are negatively charged.
  • State the Aufbau Principle.
    Electrons fill orbitals in order of increasing energy.
  • State the Pauli Exclusion Principle.
    A maximum of two electrons can occupy an orbital, and they must have opposite spins.
  • State Hund's Rule.
    Electrons fill orbitals of equal energy singly before pairing up.
  • What does the Heisenberg Uncertainty Principle state?
    It is impossible to simultaneously know an electron's exact position and momentum.
  • What is a wave function in quantum mechanics?
    An equation that describes the energy state of an electron and the probability of finding it in a region.
  • What is an atomic orbital shape?
    A 3D plot of the wave function showing where the electron is most likely to be found.
  • 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 to form molecular orbitals by addition or subtraction.
  • Define 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 noble gas electron configuration with 8 valence electrons.
  • How many octet electrons do first-row elements like H, He, and Li prefer?
    They prefer to possess 2 octet electrons.
  • What are formal charges and how are they calculated?
    Formal charge = Group number - (number of valence electrons + 1/2 bonding electrons).
  • What is the skeletal (bondline) structure convention?
    Carbons are implied at line ends and bends; hydrogens on carbons are implied; heteroatoms and hydrogens on them are shown explicitly.
  • What determines the stability of different octet electron arrangements?
    The number of owned electrons by an atom (lone pairs + one electron per bond) determines the most stable octet.