
                             CHEM 110
                 Answers to Ninth Take Home Quiz

1. Name the three types of radiation emitted by radioactive
   isotopes and give a brief description of each.
   and give a brief description of each.

    alpha radiation - high speed particles emitted by unstable 
                      nucleus. Consists of 2 neutrons & 2 protons.

    beta radiation  - high speed electrons emitted by unstable
       nucleus when a neutron disintegrates into a proton and an
       electron. The proton remains in the nucleus.

    gamma radiation - photons emitted from excited nuclei as the
                      nuclei return to their ground states.

2. State the periodic law.
    When the elements are arranged in order of increasing atomic 
    mass, there is a periodic repetition of the properties.

3. Name the two scientists who are given the most credit for
   discovering the periodic law.
                       Mendeleev and Meyer

4. What did the blanks in Mendeleev's periodic table indicate to
   him ?
        The blanks indicated to him that there were elements yet
   to be discovered which occupy these blanks in the table.
   Furthermore, he was able to predict the properties of these
   undiscovered elements.

5. List five physical properties and one chemical property of the
   metallic elements.
    1. Highly reflective of light
    2. Good conductors of heat and electricity
    3. Malleable and ductile
    4. All are solid at 20 ųC except mercury
    5. Most have high densities
    6. They combine with nometallic elements to form ionic
       compounds.  Their atoms have a tendency to lose valence
       electrons to form positive ions (cations).

6. List three physical properties and two chemical properties of 
   the nonmetallic elements.
    1. Good insulators of heat and electricity
    2. Many are gases at room temperature
    3. They combine with metallic elements to form ionic
       compounds.  Nonmetallic atoms have a tendency to unite to
       form molecules.  In the molecules atoms share valence
       electrons.

7. Name the group of metallic elements which are the most
   chemically reactive.

    Group 1, the alkali metals

8. Write the formulae for the following polyatomic ions.  Be sure
   to indicate the charges.

    ammonium    NH₄⁺                    hydroxide   OH^{-

    cyanide     CN^-                     sulfate     SO₄^2-

    nitrate     NO₃^-                    carbonate   CO₃^2-

    phosphate   PO₄^3-

9. Write electronic configurations for the following ions.
                                    
    Na⁺ 1s²2s²2p⁶     Mg²⁺  1s²2s²2p⁶     K⁺  1s²2s²2p⁶3s²3p⁶

10. Write a balanced equation for the reaction of sodium metal 
    with metal.

              2Na(m) + 2H₂O  --->  2NaOH   +   H₂(g)}