atomic theory – sample test questions -...
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ATOMIC THEORY – SAMPLE TEST QUESTIONS A. History of the Atom
1. Dalton -‐ First to believe that elements are made up of extremely small particles called
“atoms”
2. Thomson -‐ Discovered that atoms have negatively charged “electrons”
3. Rutherford proved that the atom has a tiny, positively charged nucleus surrounded by
a “cloud” of negatively charged electrons.
4. Bohr -‐ Electrons “orbit” at fixed energy levels at a certain distance from the nucleus.
B. Sub-‐atomic Particles and Average Atomic Mass:
1. Calculate the average atomic mass, given the data for the naturally occurring
isotopes: 20Ne (90.02%), 21Ne (0.257%), 22Ne (8.82%)
20 (0.9002) + 21 (0.00257) + 22 (0.0882)
18.004 + 0.05397 + 1.9404 = 20 g
C. Bohr Diagrams and Energy Level Diagrams
1. Describe the three rules to be used for determining electron assignment:
i) Aufbau Principle: Add electrons to lowest energy level first
ii) Pauli Exclusion Principle: Maximum two electrons in each orbital subshell
iii) Hund’s Rule: Electrons singly occupy orbitals, as 2nd electron added to subshells so
that each electron has opposite spin
2. Draw a Bohr Diagram AND Energy Level Diagrams for the following:
a. Ca b. F-‐
D. Electron Configuration
1. Write ONE rule for writing the electron configuration for NEGATIVE IONS (anions):
Add e-‐ to the last unfilled subshell, starting where the neutral atom left off
2. Write TWO rules for writing the electron configuration for POSITIVE IONS (cations):
1. E-‐ in the outermost shells (largest n value) are removed first
2. If there are e-‐ in both the s and p orbitals of the outermost shell, the e-‐ in the p
orbitals are removed first
p before s before d
3. The electron configuration of Cr illustrates an exception to the rule. Describe this exception and why it exists.
Cr: [Ar] 4s2 3d4 is actually [Ar] 4s1 3d5
A filled or exactly half filled d-‐subshell is especially stable. Because of this extra stability, an atom or ion that is one e-‐ short of a d5 or d10 configuration will shift an e-‐ from the s-‐subshell having the highest energy iinto the unfilled d-‐subshell.
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