Introductory Chemistry

Quiz: Atoms and subatomic particles

Cracolice 2/e Ch 5.

Answer key
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Quiz is "closed book" except for PT & calculator (although the calculator really isn't needed for this particular quiz). If a question requests an explanation, there may be no credit unless you have provided an explanation.

The three subatomic particles of major interest in chemistry are the electron, neutron and proton. Several of the questions below refer to these particles. It is fine to refer to them by their first letter, E, N, P. When the charge is of interest, we sometimes show it with the abbreviation. as a superscript: E-, N0, P+.

I use the terms mass and weight interchangeably. That is common in chemistry.

1. Which two of these particles must be in equal numbers in an atom? Why?

2. Which of these particles is/are in the outer part of the atom?

3. Which two of these particles have approximately the same mass?

4. Sketch an atom of beryllium-6 (6Be), showing the main features. [Goal: Try to do this at about the level we have discussed (text, class). Major things, how many, where? Check that your picture here is consistent with what you said in the previous questions.]

5. In the answer to the previous question, I said "Nearly all Be atoms in nature are 9Be. (The atomic weight shown on the PT is near 9.)" In this question, let's explore what that does -- and does not -- mean. In each part, tell whether the statement is true. If it is, explain why; if it is not, give a counter-example (an example that shows it is not true). Your example can be hypothetical.

a. If nearly all Be atoms in nature are 9Be, then it follows that the atomic weight is near 9.

b. If the atomic weight shown on the PT is near 9, then it follows that nearly all Be atoms in nature are 9Be.

6. Consider an atom that has 27 protons.

a. What element is this? Give the name and symbol. (Be sure that the symbol is written very clearly.)

b. How many neutrons are in that atom? Explain. (Careful!)

7. Consider an atom of 14C.

a. Does it have more protons than an "average" carbon atom, or fewer, or??? Explain.

b. Does it have more neutrons than an "average" carbon atom, or fewer, or??? Explain.

8. Consider the elements magnesium and manganese. The chemical behavior of which (one) of those elements is easier to predict? For example, which one is more likely to form only one compound with chlorine, a compound that can be easily predicted? How can you tell? (You don't need to make the prediction. You just need to know which is more predictable -- and why.)

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Last update: August 14, 2011