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chem study guide


  • Who discovered that the center of the atom was very small and dense with an overall positive charge in his gold foil experiment?

    • Rutherford

  • What subatomic particle with a positive charge is called the _____?

    • Porton

  • The _____ is always equal to the number of protons + the number of neutrons that the atom has.

    • Mass #

  • An atom that gains an electron will have a ____ charge.

    • Negative 

  • According to Dalton, atoms of different elements will be ______.

    • Different 

  • The _____ ____ of an element is the weighted average of the masses of the different isotopes of that element.

    • Atomic mass

  • What is found in the arom’s nucleus?

    • Neutrons and protons

  • Atomic # of an atom = ______

    • Protons

  • What is approximately the mass of a proton?

    • 1 amu (atomic mass unit)

  • What did Thomson discover in his cathode ray experiment?

    • The electron

  • What are atoms that have the same atomic number but different mass?

    • Isotopes

  • What did Democritus say were the indivisible, fundamental units of matter?

    • Atoms

  • An anion is an atom with an overall _____ charge.

    • Negative 

  • An atom gets an overall positive by what?

    • Loosing electrons

  •  Explain the whole major point of Dalton’s atomic theory

    •  All elements are made of tiny, invisible atoms

    •  atoms of the same element are the same, and atoms of different elements are different

    •  atoms of different elements can combine in whole number ratios to make compounds

    •  and chemical reactions, atoms are rearranged, and atoms of one element are never changed into another element

  •  What is the Rutherford Gold foil experiment?  explain what was going on when particles were deflected at small angles and large ones

    •  He shot a high beam of alpha particles into gold foil

      •  Most particles went straight through →  atoms are mostly space

      •  Some deflected at small angles →  there's a small positive center

      •   A few bounced back →  atoms have a tiny, dense, positive nucleus

  •  How did Thomson know the charge of the particle he discovered was negative?

    •  He knew this because the particles in the gas were attracted to the positive plate. He then assumed the particles have a negative charge because of the theory that opposites attract.

  •  Compare and contrast ions and isotopes. What subatomic particle changes in each?

    •  Ions – atoms with a charge

    •  . Isotopes – atoms of the same element, but with different masses. Members

      •  in ions, electrons change. But in isotopes, neutrons change.

  •  What is the difference between atomic mass and mass number?

    •  A. A. M.  is a weighted average

    •  The mass number is protons + neutrons and should be a whole number