Chang - ChemQuest

ChemQuest - Chapter 2

1. Use Alta Vista to determine the following about the element Seaborgium:

(a) the symbol of the element
(b) the atomic number
(c) the stability of the element
(d) the Nobel chemist for whom the element was named
Having obtained the information above, answer the following questions:
(e) How many protons are present in the nucleus of Seaborgium?
(f) If an atom of Seaborgium has the same number of neutrons as protons, what is its mass number?
(g) Is it likely that most Seaborgium atoms have equal numbers of protons and neutrons? [Hint: You might want to look at a periodic chart (use the one at http://www.shef.ac.uk:80/~chem/web-elements)].

2. Use the Web Elements periodic chart at http://www.shef.ac.uk:80/~chem/web-elements to determine the number of stable isotopes of the fourth element in Group IV. Interestingly, this element has the largest number of stable isotopes of any element.

3. Many inorganic compounds are prepared in water. When the ions come together to make the solid compound, water molecules are incorporated into the structure of the solid. For many compounds these "hydrates" exist as well-defined compounds. Use the American Chemical Society's (the largest professional organization of chemists in the United States) publication, Chemcyclopedia, at pubs.acs.org/chemcy/ to determine how many different hydrates of copper sulfate are commercially available (at least according to the source). Also answer the following questions:

(a) What is the formula of copper sulfate?
(b) Use the format MX·nH₂O to indicate the formula of copper sulfate pentahydrate. (M=cation, X=anion)
(c) How do you suppose you could prepare the anhydrous form of copper sulfate from one of the hydrates?

4. The word "element" has several meanings. To the layman, it probably means a simple form of matter and conjures up phrases such as "trace elements" or "the element that prevents tooth decay is fluorine". Chemistry students realize that at the atomic level of one element is different from another because of the different number of protons in the nucleus. They also know that in their uncombined or elemental forms, they may exist as atoms, as molecules, or as metals. They may also exist in all three states of matter. For example, at room temperature, elemental fluorine is a gas, elemental bromine is a liquid, and elemental iodine is a solid. Go to the site at http://library.advanced.org/2923/. Click on Equations and More and then on Diatomic Elements.

As you can see, seven elements exist in their uncombined state as diatomic molecules. For example, the nitrogen in the air we breathe is usually written as N₂ to indicate that a molecule of elemental nitrogen contains two nitrogen atoms.

(a) Because oxygen exits as a diatomic molecule, is it reasonable to suppose that sulfur would also be diatomic?
(b) In fact, a number of the nonmetals exist as molecules that are not diatomic. Sulfur exists as a cyclic chain of eight atoms. Write a formula for sulfur, and draw a structure for the molecule.
(c) Chemists sometimes name these simple molecules by using a prefix to indicate how many atoms are in one molecule. For example, N₂ is called dinitrogen. Use the prefixes on this same web page to name P₄.
(d) In the elemental form, phosphorus exists as P₄ molecules in which each phosphorus is attached to three other phosphorus atoms. Draw a structure for this molecule.
(e) Actually, many elements exist in more than one elemental form, called allotropes. For example, oxygen exists in two allotropic forms, O₂ and O₃. How are you familiar with O3?

5. The web contains many periodic charts. The one at http://www.shef.ac.uk/~chem/web-elements/ contains a variety of kinds of information about each element. Use the chart to answer the following:

(a) What is the origin of the symbol K for potassium? Why not use P or Po?
(b) Name the elements in Group I.
(c) How do the ionization energies vary for the Group I elements? Do all groups show this kind of variation?
(d) How many electrons would the cation of the element with an atomic weight of 24.305 have?
(e) How many electrons would the anion of the element with 53 protons have?

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