MCAT quantum numbers and electron configuration
Study the essential concepts of quantum numbers and electron configuration for the MCAT, focusing on high-yield facts and relationships that commonly appear in passage questions.
Quiz(72 questions)
1. Which quantum number defines the size of the orbital?
Terms in this Study Set(72)
Quantum Numbers(16)
What are the four quantum numbers?
Principal quantum number (n), azimuthal quantum number (l), magnetic quantum number (m_l), spin quantum number (m_s).
Principal quantum number (n) indicates what?
The energy level and distance of the electron from the nucleus. Values: 1, 2, 3, ... (positive integers).
True or false: l can equal n.
False. l ranges from 0 to n-1.
Fill in the blank: l = 0 corresponds to which subshell?
s subshell.
What does the magnetic quantum number (m_l) specify?
The orientation of the orbital in space. Values range from -l to +l.
Comparison: m_l vs. m_s
m_l indicates orbital orientation; m_s indicates electron spin direction (±1/2).
Cause → Effect: Increasing n affects energy how?
Higher n values lead to higher energy levels and larger orbitals.
What is the maximum number of electrons per shell?
Each shell can hold up to electrons.
Azimuthal quantum number (l) and its values?
l determines the subshell type: s (0), p (1), d (2), f (3).
What does spin quantum number (m_s) represent?
The intrinsic angular momentum of an electron: +1/2 or -1/2.
True or false: Two electrons in the same orbital can have the same m_s.
False. They must have opposite spins (different m_s).
What is the significance of quantum numbers in electron configuration?
They define the state of an electron and dictate the distribution of electrons in atoms.
Example: 3p orbital quantum numbers?
n=3, l=1 (p), m_l=-1, 0, +1, m_s=±1/2.
True or false: Each quantum number is independent.
True. Each quantum number describes different properties of an electron.
Comparison: n=2 vs. n=3
n=3 has more energy levels and can hold 18 electrons; n=2 holds 8.
Principal quantum number (n) can be what values?
Positive integers: 1, 2, 3, ...
Electron Configuration(20)
What is the Aufbau principle?
Electrons fill the lowest energy orbitals first before moving to higher ones.
1s² 2s² 2p⁶ 3s² 3p⁶ represents what?
The electron configuration for the noble gas neon (Ne).
How many valence electrons does oxygen have?
Oxygen has 6 valence electrons, as indicated by its configuration: 1s² 2s² 2p⁴.
True or False: Transition metals always have 2 valence electrons.
False. Transition metals can have varying numbers of valence electrons due to d-orbitals.
Fill in the blank: The maximum number of electrons in an energy level is _____ .
2n², where n is the principal quantum number.
What is Hund's rule?
Electrons will occupy degenerate orbitals singly before pairing up.
Electron configuration for sodium (Na)?
1s² 2s² 2p⁶ 3s¹.
Comparison: 4s vs 3d orbitals?
- 4s is filled before 3d. - 3d is higher in energy after 4s.
What is a core electron?
Electrons in the inner shells, not involved in bonding or chemical reactions.
Determine the electron configuration for chlorine (Cl).
1s² 2s² 2p⁶ 3s² 3p⁵.
Cause → Effect: Filling of p-orbitals.
Causes increased electron repulsion leading to higher energy states.
What do the superscripts in electron configurations denote?
The number of electrons in each subshell (e.g., 2 in 2p²).
True or False: The electron configuration of an element can predict its reactivity.
True. Elements with similar configurations often exhibit similar chemical properties.
Identify the element: 1s² 2s² 2p⁶ 3s² 3p¹.
This is aluminum (Al); it has 13 electrons.
What is the electron configuration for a neutral atom of iron (Fe)?
1s² 2s² 2p⁶ 3s² 3p⁶ 4s² 3d⁶.
How to find valence electrons in an element?
Look at the highest principal energy level in the electron configuration.
Fill in the blank: The electron configuration for argon (Ar) is _____ .
1s² 2s² 2p⁶ 3s² 3p⁶.
What is the significance of the periodic table columns?
Elements in the same column have similar valence electron configurations.
Identify the element with 10 electrons.
This is neon (Ne) with the configuration 1s² 2s² 2p⁶.
How to write the electron configuration for a transition metal?
Transition metals use the following order: 4s fills before 3d. Example: Iron (Fe) = 1s² 2s² 2p⁶ 3s² 3p⁶ 4s² 3d⁶. Remember to account for oxidation states when determining configurations.
Periodic Trends and Quantum Theory(20)
How does atomic size change across a period?
Atomic size decreases from left to right due to increased nuclear charge, pulling electrons closer.
What trend occurs in ionization energy down a group?
Ionization energy decreases down a group because outer electrons are further from the nucleus and experience more shielding.
True or False: Electronegativity increases down a group.
False. Electronegativity decreases down a group due to increased distance from the nucleus.
Compare ionization energy and electronegativity.
Ionization energy: energy to remove an electron. Electronegativity: tendency to attract electrons.
As atomic number increases, what happens to atomic radius?
Atomic radius generally increases due to added electron shells.
What is the electron configuration of a fluorine atom?
1s² 2s² 2p⁵
Cause → Effect: Increased nuclear charge.
Effect: Decreased atomic size across a period.
What is the trend in electronegativity across a period?
Electronegativity increases across a period as atoms gain more protons.
Fill in the blank: Ionization energy is highest for ____ elements.
noble gases
How do quantum numbers relate to atomic size?
Higher principal quantum number (n) increases distance from nucleus, increasing size.
What happens to the first ionization energy of alkali metals?
First ionization energy decreases down the group due to increased electron shielding.
True or False: Helium has a higher electronegativity than hydrogen.
True. Helium, being a noble gas, is less reactive but has a high electronegativity.
Compare the atomic radius of Na and Cl.
Sodium (Na) has a larger atomic radius than chlorine (Cl) due to fewer protons.
What is the general trend of atomic radius?
Atomic radius increases down a group and decreases across a period.
What quantum number describes the shape of an orbital?
The azimuthal quantum number (l) describes the shape of an orbital.
Fill in the blank: Larger atomic radii correlate with ____ ionization energy.
lower
What is the electron configuration of oxygen?
1s² 2s² 2p⁴
Cause → Effect: Increased distance from the nucleus.
Effect: Decreased ionization energy.
How does electron shielding affect ionization energy?
Increased shielding reduces effective nuclear charge, lowering ionization energy.
What is the periodic trend for electronegativity?
Electronegativity increases across a period and decreases down a group.
Practice Problems(16)
Calculate the maximum number of electrons in a given shell.
Formula: . For n=3, max electrons = .
True or False: The 4th quantum number describes the orientation of an orbital.
False. The 4th quantum number (m_s) describes the spin of the electron.
Which quantum number determines the shape of an orbital?
The azimuthal quantum number (l) determines the shape. l = 0 (s), 1 (p), 2 (d), 3 (f).
Fill in the blank: The principal quantum number (n) indicates the ______ of an electron.
distance from the nucleus.
Determine the electron configuration for Carbon (C).
1s² 2s² 2p². Total 6 electrons.
Cause → Effect: What happens to electron configuration as you move down a group?
Effect: Increased principal quantum number (n), leading to larger atomic size.
List the four quantum numbers for the last electron in Cl.
n=3, l=0, m_l=0, m_s=+1/2.
True or False: An electron in the 3d orbital has more energy than one in the 4s orbital.
True. 3d orbitals are higher in energy than 4s.
What is the role of the Pauli Exclusion Principle?
No two electrons in an atom can have the same set of four quantum numbers.
For an atom with 10 electrons, what is the maximum value of l?
l can be up to 3 (s, p, d). For 10 electrons, l=2 (2s, 2p, 3s).
Identify the electron configuration for the ground state of Neon (Ne).
1s² 2s² 2p⁶. Total 10 electrons.
Compare: 3p vs 4s orbitals.
4s is filled before 3p due to lower energy level at initial filling.
Write the electron configuration for an ion: Na⁺.
Na: 1s² 2s² 2p⁶ 3s¹. Na⁺: 1s² 2s² 2p⁶.
How do you determine valence electrons from an electron configuration?
Count electrons in the outermost shell (highest n).
Solve: What are the quantum numbers for the last electron in Ar?
n=3, l=1, m_l=0, m_s=+1/2.
How many unpaired electrons are in a ground state oxygen atom?
Two unpaired electrons in 2p orbitals. Configuration: 1s² 2s² 2p².
Questions in this Study Set(72)
1. Which quantum number defines the size of the orbital?
2. What principle states that electrons fill the lowest energy orbitals first?
3. What happens to electronegativity as you move from left to right across a period?
4. What is the maximum number of electrons that can occupy the n=4 shell?
5. What range of values can the azimuthal quantum number (l) take?
6. Which of the following represents the electron configuration of carbon (C)?
7. Which quantum number indicates the orientation of an orbital?
8. True or False: The principal quantum number (n) indicates the shape of an orbital.
9. If n=4, what is the maximum number of electrons that can occupy this shell?
10. How many valence electrons does chlorine have?
11. True or False: The atomic radius decreases as you move down a group in the periodic table.
12. Which quantum number describes the orientation of an orbital?
13. Which of the following correctly describes the magnetic quantum number (m_l)?
14. True or False: The electron configuration for magnesium (Mg) is 1s² 2s² 2p⁶ 3s².
15. How does ionization energy change as you move down a group in the periodic table?
16. Fill in the blank: The azimuthal quantum number (l) indicates the ______ of an electron.
17. Which quantum number can indicate the subshell type?
18. What is the maximum number of electrons that can occupy the 4th energy level?
19. Which of the following elements has the highest electronegativity?
20. What is the electron configuration for an atom with 12 electrons?
21. How many different orientations can a p subshell have?
22. According to Hund's rule, how should electrons be distributed in degenerate orbitals?
23. Which statement about ionization energy is TRUE?
24. Cause → Effect: What happens to atomic radius as you move across a period from left to right?
25. True or False: The spin quantum number (m_s) can be both +1/2 and +1/2 for two electrons in the same orbital.
26. What is the electron configuration for a neutral atom of potassium (K)?
27. What is the relationship between atomic size and ionization energy?
28. List the four quantum numbers for the last electron in Ar.
29. If n=2 and l=1, what are the possible values of m_l?
30. Identify the element with the following electron configuration: 1s² 2s² 2p⁶ 3s² 3p².
31. Which of the following elements has the largest atomic radius?
32. True or False: A 4p orbital is higher in energy than a 3d orbital.
33. Which of the following statements is true regarding quantum numbers?
34. Which of the following is NOT a valid electron configuration?
35. Fill in the blank: As you move across a period from left to right, atomic size generally _____.
36. What principle states that no two electrons in an atom can have the same set of four quantum numbers?
37. What does an increase in the principal quantum number (n) imply about the energy of the electron?
38. How do you determine the number of valence electrons from an electron configuration?
39. What is the electron configuration of a sodium atom?
40. For an atom with 18 electrons, what is the maximum value of l?
41. Fill in the blank: The spin quantum number (m_s) can only be what values?
42. What does the superscript in an electron configuration represent?
43. True or False: All noble gases have full outer electron shells.
44. Identify the electron configuration for the ground state of Argon (Ar).
45. Which quantum number indicates the direction of an electron's spin?
46. True or False: The reactivity of an element can be predicted by its electron configuration.
47. Which quantum number specifies the principal energy level of an electron?
48. Compare: 4s vs 3d orbitals. Which is filled first?
49. What is the relationship between quantum numbers and electron configuration?
50. What is the electron configuration of selenium (Se)?
51. What is the trend in atomic radii as you move down a group?
52. Write the electron configuration for the Na⁺ ion.
53. If n=3, which of the following is NOT a possible value of l?
54. Which of the following correctly describes transition metals' electron configurations?
55. Which of the following elements would have the lowest ionization energy?
56. How do you determine the number of valence electrons from an electron configuration?
57. In a 4d orbital, what are the quantum numbers?
58. Which element has the electron configuration 1s² 2s² 2p⁶ 3s² 3p⁶ 4s² 3d⁸?
59. What is the azimuthal quantum number for a p orbital?
60. What are the quantum numbers for the last electron in Cl?
61. Which of the following statements about the principal quantum number (n) is correct?
62. Identify the element with 30 electrons.
63. Fill in the blank: As atomic number increases, atomic size generally _____.
64. How many unpaired electrons are in a ground state nitrogen atom?
65. What is the electron configuration for bromine (Br)?
66. Which of the following elements is most likely to gain electrons during a chemical reaction?
67. Which of the following elements has an electron configuration ending in 4s² 3d⁵?
68. What role does electron shielding play in ionization energy?
69. What is true about the electron configuration of noble gases?
70. True or False: Electronegativity is a measure of an atom's ability to attract and hold onto electrons.
71. In the electron configuration 1s² 2s² 2p⁶ 3s² 3p⁶, what does the 2p⁶ indicate?
72. Which of the following describes the trend in atomic size as you move down a group in the periodic table?
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