[Avery]

Hello, I am having some trouble with two questions of my chemistry homework. Any help what-so-ever, will help greatly!

Two compounds have formulas A2B6 and CD3.  One of these compounds is an ionic compound and one a molecular one.  How can you tell from the formulas which one is ionic?

a)  For the ionic compound, if the negative ion has a –1 charge, what is the charge of the positive ion?

b) Suggest two ions that might form this compound and draw a microscopic sketch of several formula units of this compound.

*I can find the charge and what compound it is... I have no clue how to find is its Ionic or molecular with only that info.

Millikan determined the charge on the electron by studying the static charges on oil drops falling in an electric field.  A student carried out this experiment using several oil drops for her measurements and calculated the charges on the drops.  She obtained these data.

Calculated Charge (C)

1.60 x 10-19

3.15 x 10-19

4.81 x 10-19

6.31 x 10-19

What is the significance of the fact that the droplets carried different charges?  What conclusion can the student draw from these data regarding the charge of the electron?  What value (and to how many significant figures) should she report for the electronic charge?  

*Now this question, I really don't know where to start. I can't find any on the Millikan experiment in our text and my teacher only briefly touched on it in class. Any help, and sort of direction you can point me in will be greatly appreciated. Thank you in advance...
-avery    

[Demotivator]

A2B6 is a dimer. There is no reason to express the compound as a dimer being the simplest unit that can be identified as an independent molecule instead of the simpler AB3 if it weren't for the fact that it has a molecular rather than ionic structure.

[skyaintsnow]

1(a)Hint: The molecule is neutral, that is the total charge is 0.
  (b)Hint: Ionic compounds, you are looking for one element from the left end and one element from the right end of the periodic table.

2. When we say some species carry a charge of -1, we mean this species carries one unit of electrical charge. The Millikan experiment was designed to calculate how many Columb is one unit of electrical charge, so the charge of all species can be expressed by an integer as the multiple of this unit.

Notice the data is roughly a list of multiples of 1.60 x 10^-19 Confirm this yourself. This should give you a hint of how many columbs is one unit.