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General Chemistry Key Concepts

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이 집합의 용어 (23)

  • Atomic mass unit (amu)
    Defined as exactly 1/12 the mass of a carbon-12 atom, about 1.6605 × 10⁻²⁴ g; roughly the mass of a proton or neutron
  • Ion, cation, and anion definitions
    Ion: charged atom/molecule; Cation: positive ion (lost electrons); Anion: negative ion (gained electrons)
  • Determining isotope abundance from atomic mass
    The isotope with mass closest to the average atomic mass has the greatest natural abundance
  • Avogadro's number significance
    6.022 × 10²³ particles per mole; links atomic scale to lab scale; atomic mass in amu equals mass in grams per mole
  • Electromagnetic radiation definition
    Energy traveling as oscillating electric and magnetic fields at speed of light (3.00 × 10⁸ m/s)
  • Frequency (ν) and wavelength (λ)
    Frequency: cycles per second (Hz); Wavelength: distance between wave crests (m)
  • Photon energy formula
    Energy of a photon is \(E = h\nu\), where h is Planck's constant (6.626 × 10⁻³⁴ J·s)
  • Units for frequency, wavelength, and energy

    Frequency: Hz (s⁻¹);

    Wavelength: m, nm, μm;

    Energy: J, kJ/mol

  • Ordering of electromagnetic radiation by energy

    Radio waves < Microwaves < Infrared < Visible < Ultraviolet < X-rays < Gamma rays (increasing energy, frequency; decreasing wavelength)

    Radiant Men In Vegas Use X-ray Glasses

  • Photoelectric effect explanation
    Light ejects electrons only above threshold frequency; explained by photons with energy \(E = h\nu\)
  • Bohr atomic model key points
    Electrons orbit in fixed energy levels, absorb/emit photons to change levels; violates classical physics predictions
  • Wave-particle duality
    Light and matter exhibit both wave and particle properties; de Broglie wavelength \(\lambda = \frac{h}{mv}\)
  • Why matter waves of large objects are not observed
    Large mass results in extremely small wavelength, making wave properties undetectable
  • Heisenberg Uncertainty Principle

    Impossible to know exact position and momentum simultaneously

  • Meaning of ψ² in quantum mechanics
    ψ² represents the probability density of finding an electron at a point in space (electron cloud)
  • Four quantum numbers and their significance
    n: principal energy level; l: orbital shape; m_l: orbital orientation; m_s: electron spin (+½ or -½)
  • Difference between absorption and emission of light

    Absorption: electron gains energy and moves to higher level;

    Emission: electron loses energy and drops to lower level

  • Exceptions in electron configurations for Chromium and Copper
    Chromium: [Ar] 4s¹ 3d⁵ instead of 4s² 3d⁴; Copper: [Ar] 4s¹ 3d¹⁰ instead of 4s² 3d⁹

  • pauli exlusion principal

    no two electrons can have the same four quantum numnbers. two electrons in the same orbital will have 3 quantum numbers (n,l,ml) in common so they must have different ms values (indicated in. the opposing direction of the arrows)

  • hunds rule states...

    when filling degenerate orbitals., (same energy) electronsz fill singly first with parallel spins

  • pattern of orbital filling is known as the

    aufbau principal

  • An ___ is any arrangement of an atom’s electrons that has higher energy than its lowest-energy arrangement, the ___.

    excited state; ground state

    • From radio to gamma, the frequency ___and energy ___ while wavelength ____

    • Red light has the _______

    • increases

    • increases

    • decreases (shorter)

    • longest wavelength (lowest energy)