MCAT General Chemistry Review  Alexander Stone Macnow, MD 20192020
Atomic Structure
Discrete Practice Questions
Consult your online resources for additional practice.
1. Which of the following is the correct electron configuration for Zn^{2+}?
1. 1s^{2}2s^{2}2p^{6}3s^{2}3p^{6}4s^{0}3d^{10}
2. 1s^{2}2s^{2}2p^{6}3s^{2}3p^{6}4s^{2}3d^{8}
3. 1s^{2}2s^{2}2p^{6}3s^{2}3p^{6}4s^{2}3d^{10}
4. 1s^{2}2s^{2}2p^{6}3s^{2}3p^{6}4s^{0}3d^{8}
2. Which of the following quantum number sets is possible?
1. n = 2; l = 2; m_{l} = 1;
2. n = 2; l = 1; m_{l} = −1;
3. n = 2; l = 0; m_{l} = −1;
4. n = 2; l = 0; m_{l} = 1;
3. What is the maximum number of electrons allowed in a single atomic energy level in terms of the principal quantum number n?
1. 2n
2. 2n + 2
3. 2n^{2}
4. 2n^{2} + 2
4. Which of the following equations describes the maximum number of electrons that can fill a subshell?
1. 2l + 2
2. 4l + 2
3. 2l^{2}
4. 2l^{2} + 2
5. Which of the following atoms only has paired electrons in its ground state?
1. Sodium
2. Iron
3. Cobalt
4. Helium
6. An electron returns from an excited state to its ground state, emitting a photon at λ = 500 nm. What would be the magnitude of the energy change if one mole of these photons were emitted? (Note: h = 6.626 × 10^{−34} J · s, N_{A} = 6.02 × 10^{23} mol^{−1})
1. 3.98 × 10^{−21} J
2. 3.98 × 10^{−19} J
3. 2.39 × 10^{3} J
4. 2.39 × 10^{5} J
7. Suppose an electron falls from n = 4 to its ground state, n = 1. Which of the following effects is most likely?
1. A photon is absorbed.
2. A photon is emitted.
3. The electron moves into a porbital.
4. The electron moves into a dorbital.
8. Which of the following isotopes of carbon is LEAST likely to be found in nature?
^{1. 6}C
^{2. 12}C
^{3. 13}C
^{4. 14}C
9. Which of the following best explains the inability to measure position and momentum exactly and simultaneously according to the Heisenberg uncertainty principle?
1. Imprecision in the definition of the meter and kilogram
2. Limits on accuracy of existing scientific instruments
3. Error in one variable is increased by attempts to measure the other
4. Discrepancies between the masses of nuclei and of their component particles
10. Which of the following electronic transitions would result in the greatest gain in energy for a single hydrogen electron?
1. An electron moves from n = 6 to n = 2.
2. An electron moves from n = 2 to n = 6.
3. An electron moves from n = 3 to n = 4.
4. An electron moves from n = 4 to n = 3.
11. Suppose that an atom fills its orbitals as shown:
Such an electron configuration most clearly illustrates which of the following laws of atomic physics?
1. Hund’s rule
2. Heisenberg uncertainty principle
3. Bohr model
4. Rutherford model
12. How many total electrons are in a ^{133}Cs cation?
1. 54
2. 55
3. 78
4. 132
13. The atomic weight of hydrogen is 1.008 amu. What is the percent composition of hydrogen by isotope, assuming that hydrogen’s only isotopes are ^{1}H and ^{2}D?
1. 92% H, 8% D
2. 99.2% H, 0.8% D
3. 99.92% H, 0.08% D
4. 99.992% H, 0.008% D
14. Consider the two sets of quantum numbers shown in the table, which describe two different electrons in the same atom.
n 
l 
m_{l} 
m_{s} 
2 
1 
1 

3 
1 
−1 
15. Which of the following terms best describes these two electrons?
1. Parallel
2. Opposite
3. Antiparallel
4. Paired
15. Which of the following species is represented by the electron configuration 1s^{2}2s^{2}2p^{6}3s^{2}3p^{6}4s^{1}3d^{5}?
1. Cr
2. Mn^{+}
3. Fe^{2+}
4. I only
5. I and II only
6. II and III only
7. I, II, and III