Skip to main content
Back

General Chemistry: Atoms and Elements Key Concepts

Control buttons has been changed to "navigation" mode.
1/28
  • Law of Conservation of Mass
    Matter is neither created nor destroyed in a chemical reaction.
  • Law of Definite Proportions
    All samples of a given compound have the same proportions of their constituent elements.
  • Law of Multiple Proportions
    When two elements form different compounds, the masses of one element that combine with a fixed mass of the other are in ratios of small whole numbers.
  • Dalton's Atomic Theory - False Statement
    An atom can be broken down into smaller particles that retain the unique properties of that element is false.
  • Thomson's Discovery about Electrons
    Electrons carry a negative charge and are about 2000 times lighter than hydrogen atoms.
  • Millikan's Experiment
    Oil droplets were sprayed into fine droplets and their charge was measured to determine the charge of a single electron.
  • Modern Atomic Model of an Atom
    An atom has protons and neutrons in the nucleus and electrons in orbitals surrounding the nucleus.
  • Largest Subatomic Particle
    The neutron is the largest subatomic particle.
  • Smallest Subatomic Particle
    The electron is the smallest subatomic particle.
  • Mass Number
    The sum of the number of protons and neutrons in an atom.
  • Atomic Number
    The number of protons in an atom.
  • Isotopes
    Atoms of the same element that differ in the number of neutrons.
  • Ions vs Isotopes
    Ions differ by the number of electrons; isotopes differ by the number of neutrons.
  • Charge of Protons, Neutrons, and Electrons
    Protons have +1 charge, neutrons have 0 charge, electrons have -1 charge.
  • Cation
    An atom that has lost one or more electrons and has a positive charge.
  • Anion
    An atom that has gained one or more electrons and has a negative charge.
  • Atomic Mass Determination
    The atomic mass is the weighted average mass of the isotopes of an element.
  • Mass Spectrometer
    An instrument used to measure the mass of atoms and the percent abundance of isotopes.
  • Avogadro's Number
    6.022 × 10\(^{23}\), the number of particles in one mole.
  • Predicting Ion Charges for Aluminum and Phosphorus
    Aluminum typically forms a 3+ ion; phosphorus typically forms a 3- ion.
  • Properties of Metals
    Good conductors of heat and electricity, tend to lose electrons, and are found on the left side of the periodic table.
  • Properties of Nonmetals
    Poor conductors of heat and electricity, tend to gain electrons, and are found on the right side of the periodic table.
  • Metalloids
    Elements with properties intermediate between metals and nonmetals; semiconductors.
  • Noble Gases
    Group of elements that are very unreactive due to their full valence electron shells.
  • Halogens
    Group 17 elements such as F, Cl, Br, and I that are reactive nonmetals.
  • Determining Number of Protons, Neutrons, and Electrons
    Protons = atomic number; Neutrons = mass number − atomic number; Electrons = protons ± charge.
  • Isotopes Have Same Atomic Size Because
    They have the same number of electrons; size is determined by electrons, not neutrons.
  • Anions Compared to Atoms
    Anions are larger than their corresponding atoms due to increased electron-electron repulsion.