chem hw 12

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chem hw 12
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2010-04-12 00:09:03
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chem HW 12
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  1. Review 2. Is it possible to see an atom using visible light?
    No, the wave length of visible light is larger than the size of atoms
  2. Review 3. What is the center of every atom?
    A nucleus containing positively charged protons and neutral neutrons.
  3. Review 4. How many types of atoms can you expect to find in a pure sample of any element?
    A pure sample of any element is only one kind of atom.
  4. Review 7. What role does atomic number play in the periodic table?
    The atomic number tells the number of protons which describes the specific element.
  5. Review 8. Distinguish between atomic number and mass number.
    Atomic number is the number of protons, where the mass number is the number of protons and neutrons.
  6. Review 9. Distinguish between mass nmber and atomic number.
    The mass number is the number of nucleons (protons + neutrons). The atomic mass is teh average mass of the atom based on the relative abundance of the element's isotopes.
  7. Review 10. Are most elements metallic or nonmetallic?
    Most of the elements are metallic.
  8. Review 15. What is the difference between a physical model and a conceptual model?
    A physical model is a representation of an object of some convenient scale. A conceptual model is a representation of a system that helps us predict how the system behaves.
  9. exercises 2. If all the molecules of a body remained part of that body, would the body have any odor?
    A body would have no odor if all its molecules remained intact. A body has odor only if some of its molecules enter a nose.
  10. exercise 8. If two protons and two neutrons are removed from the nucleus of an oxygen-10 atom, a nucleus of which element remains?
    The remaining nucleuse is that of Carbon-12
  11. Review 9. If an atom has 43 electrons, 56 neutrons, and 43 protons, what is its approximate atomic mass? What is the name of this element?
    Atomic mass would be 99 amu, and the element would be technetium, Tc, atomic number 43.
  12. Review 10. The nucleus of an electrically neutral iron atom contains 26 protons. How many electorns does this iron atom have?
    The iron atom is electrically neutral when it has 26 electrons to balance 26 protons.
  13. Exercises 12. Which has more atoms: a 1 g sample of carbon-12 or a 1 g sample of carbon-13? Explain.
    Carbon-13 atoms have more mass than carbon-12 atoms. Because of this, a given mass of carbon-13 contains fewer atoms than the same mass of carbon-12. Look at it this way -- golf balls have more mass than ping pong balls. So, which contains more balls: 1 kilogram of golf balls or 1 kilogram of ping pong balls? Because ping pong balls are so much lighter, you needmany more of them to get 1 kilogram.
  14. Exercises 14. Which contributes more to an atom's mass: electrons or protons? Which contributes more to an atom's size?
    Protons, which are nearly 2000 times more massive than electrons, contribute much more to the mass of an atom. Protons, however, are held within the atomic nucleus, which is only a tiny tiny fraction of the volume of the atom. The size of the atom is spelled out by the electrons which sweep throuh a relatively large volume of space surrounding the nucleus.
  15. Exercises 20. Does it make sense to say that this textbook is about 99.9% empty space?
    Yes, the textbook is made of about 99.9 percent empty space. In fact, anything made of atoms is mostly empty space, including our bodies.
  16. Exercises 21. The atoms that compose your body are mostly empty space, and structures such as the chair you're sitting on are composed of atoms that are also mostly empty smace. So why don't you fall through the chair?
    The electric force of repulsion between the electrons of the chair and you prevent your atoms from falling through each other.

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