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General Chemistry: Atoms and Elements

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Termini in questo insieme (24)

  • What is an atom?

    An atom is the smallest particle of matter that retains all the properties of an element.

  • Define an element.

    An element is a fundamental form of matter composed of one kind of atom.

  • What does the Law of Conservation of Mass state?

    Matter is neither created nor destroyed in a chemical reaction.

  • What is the Law of Definite Proportions?

    All samples of a given compound have the same proportions of their constituent elements.

  • Explain the 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.

  • List the main points of Dalton's Atomic Theory.
    1. Matter is composed of indivisible atoms.
    2. Atoms of an element are identical.
    3. Atoms of different elements differ.
    4. Atoms combine in whole-number ratios.
    5. Atoms are rearranged in reactions, not created or destroyed.
  • What did J.J. Thomson discover about cathode rays?

    Cathode rays are composed of negatively charged particles called electrons that travel in straight lines and are independent of the cathode material.

  • What was the Plum Pudding Model?

    A model where electrons are embedded in a positively charged spherical cloud.

  • What did Millikan's Oil Drop Experiment measure?

    The charge of a single electron.

  • What was Rutherford's conclusion from the gold foil experiment?

    Atoms have a small, dense, positively charged nucleus and are mostly empty space.

  • What are the three main subatomic particles and their charges?
    • Proton: positive charge (+1)
    • Neutron: neutral (0)
    • Electron: negative charge (-1)
  • What defines an element's identity?

    The number of protons in its nucleus, called the atomic number (Z).

  • What is an isotope?

    Atoms of the same element with the same number of protons but different numbers of neutrons.

  • How is atomic mass calculated?

    It is the weighted average mass of an element's isotopes based on their natural abundance.

  • What is the periodic law?

    When elements are arranged by increasing atomic mass, certain properties recur periodically.

  • How did Mendeleev contribute to the periodic table?

    He arranged elements by increasing mass and grouped elements with similar properties, predicting undiscovered elements.

  • What are groups and periods in the periodic table?

    Groups are vertical columns with similar properties; periods are horizontal rows.

  • What are alkali metals and their key properties?

    Highly reactive metals in Group 1A, good conductors, malleable, ductile, and tend to lose electrons.

  • What are halogens?

    Very reactive nonmetals in Group 7A, including fluorine, chlorine, bromine, iodine, and astatine.

  • What are noble gases?

    Inert, chemically stable gases in Group 8A that rarely form compounds.

  • What is the mole?

    A unit representing Avogadro's number of particles, equal to the number of atoms in exactly 12 grams of carbon-12.

  • What is molar mass?

    The mass in grams of one mole of atoms of an element, numerically equal to its atomic mass in amu.

  • How do you convert between moles and number of atoms?

    Use Avogadro's number as a conversion factor: 1 mole = 6.022 x 10\(^{23}\) particles.

  • How do you convert between mass and moles?

    Use the molar mass as a conversion factor: mass (g) = moles × molar mass (g/mol).