Atomic structure
62 flashcards covering Atomic structure for the MCAT Chem / Phys / Psych / Soc section.
Atomic structure is the fundamental makeup of atoms, the basic building blocks of all matter. At the core is the nucleus, containing protons (positively charged) and neutrons (neutral), while electrons (negatively charged) orbit in specific energy levels or shells. This arrangement determines an element's chemical behavior, such as how it bonds with other atoms, and is essential for understanding larger concepts like chemical reactions and molecular stability.
On the MCAT, atomic structure questions typically appear in the Chemical and Physical Foundations section, often as multiple-choice items testing electron configurations, periodic trends, and subatomic particle properties. Common traps include confusing atomic mass with atomic number or misunderstanding quantum numbers, so pay attention to details like orbital filling rules. Focus on applying these concepts to passage-based scenarios, such as interpreting spectra or predicting reactivity, as they integrate with biology and physics.
Practice sketching electron configurations to reinforce key patterns.
Terms (62)
- 01
Atom
An atom is the basic unit of matter, consisting of a dense nucleus surrounded by a cloud of electrons.
- 02
Nucleus
The nucleus is the central part of an atom, containing protons and neutrons, and it holds most of the atom's mass.
- 03
Proton
A proton is a positively charged subatomic particle found in the nucleus of an atom, with a mass of approximately 1 atomic mass unit.
- 04
Neutron
A neutron is a neutral subatomic particle found in the nucleus of an atom, with a mass similar to that of a proton.
- 05
Electron
An electron is a negatively charged subatomic particle that orbits the nucleus of an atom and determines its chemical properties.
- 06
Atomic number
The atomic number of an element is the number of protons in the nucleus of its atoms, which defines the element's identity.
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Mass number
The mass number of an atom is the total number of protons and neutrons in its nucleus.
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Isotope
Isotopes are atoms of the same element that have the same number of protons but different numbers of neutrons.
- 09
Ion
An ion is an atom or molecule that has gained or lost one or more electrons, resulting in a net electrical charge.
- 10
Electron shell
An electron shell is a region around the nucleus of an atom where electrons with a specific energy level are likely to be found.
- 11
Orbital
An orbital is a three-dimensional region around an atom's nucleus where there is a high probability of finding an electron.
- 12
Principal quantum number
The principal quantum number, denoted as n, indicates the energy level and average distance of an electron from the nucleus.
- 13
Azimuthal quantum number
The azimuthal quantum number, denoted as l, defines the shape of an electron's orbital and ranges from 0 to n-1.
- 14
Magnetic quantum number
The magnetic quantum number, denoted as ml, specifies the orientation of an orbital in space and ranges from -l to +l.
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Spin quantum number
The spin quantum number, denoted as ms, describes the intrinsic spin of an electron, which can be either +1/2 or -1/2.
- 16
Aufbau principle
The Aufbau principle states that electrons fill atomic orbitals starting from the lowest energy levels before moving to higher ones.
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Pauli exclusion principle
The Pauli exclusion principle asserts that no two electrons in an atom can have the same set of four quantum numbers.
- 18
Hund's rule
Hund's rule states that electrons will fill orbitals of the same energy singly before pairing up, to maximize total spin.
- 19
Bohr model
The Bohr model describes the atom as a nucleus with electrons orbiting in discrete energy levels, like planets around the sun.
- 20
Quantum mechanical model
The quantum mechanical model portrays electrons as having wave-like properties and existing in probability clouds rather than fixed orbits.
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Ground state
The ground state is the lowest energy state of an atom, where its electrons are in the most stable configuration.
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Excited state
An excited state occurs when an atom's electrons absorb energy and move to higher energy levels than in the ground state.
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Electron configuration
Electron configuration is the distribution of electrons in the atomic orbitals of an atom, following the rules of quantum mechanics.
- 24
Valence electrons
Valence electrons are the electrons in the outermost shell of an atom, which participate in chemical bonding.
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Core electrons
Core electrons are the electrons in the inner shells of an atom, which are not involved in chemical reactions.
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Effective nuclear charge
Effective nuclear charge is the net positive charge experienced by an electron in a multi-electron atom, reduced by the shielding effect of inner electrons.
- 27
Shielding effect
The shielding effect is the reduction in the attraction between the nucleus and an electron due to the repulsion from inner electrons.
- 28
Atomic radius
Atomic radius is the distance from the nucleus to the outermost electron shell, which generally increases down a group in the periodic table.
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Photoelectric effect
The photoelectric effect is the emission of electrons from a metal surface when light of sufficient frequency strikes it, demonstrating the particle nature of light.
- 30
Wave-particle duality
Wave-particle duality means that particles like electrons exhibit both wave-like and particle-like properties, depending on the experiment.
- 31
De Broglie wavelength
The De Broglie wavelength is the wavelength associated with a particle, calculated as Planck's constant divided by the particle's momentum.
- 32
Heisenberg uncertainty principle
The Heisenberg uncertainty principle states that it is impossible to simultaneously know both the exact position and exact momentum of a particle.
- 33
Nuclear stability
Nuclear stability refers to the tendency of an atomic nucleus to resist decay, influenced by the balance of protons and neutrons.
- 34
Radioactivity
Radioactivity is the process by which unstable atomic nuclei emit radiation to become more stable.
- 35
Alpha decay
Alpha decay is a type of radioactive decay where an atomic nucleus emits an alpha particle, consisting of two protons and two neutrons.
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Beta decay
Beta decay occurs when a neutron in the nucleus transforms into a proton and emits an electron, or when a proton emits a positron.
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Gamma decay
Gamma decay is the emission of high-energy gamma rays from an excited nucleus to reach a lower energy state.
- 38
Half-life
Half-life is the time required for half of the radioactive atoms in a sample to decay.
- 39
Binding energy
Binding energy is the energy required to break apart the nucleus of an atom into its individual protons and neutrons.
- 40
Mass defect
Mass defect is the difference between the mass of an atom and the sum of the masses of its protons, neutrons, and electrons, converted to energy.
- 41
Common trap: Atomic mass vs. atomic weight
Atomic mass refers to the mass of a specific isotope, while atomic weight is the average mass of an element's naturally occurring isotopes.
- 42
Strategy for electron configuration
To write an electron configuration, follow the Aufbau principle, fill orbitals in order of increasing energy, and apply Hund's rule and the Pauli exclusion principle.
- 43
Orbital shapes
Orbital shapes describe the three-dimensional forms of electron orbitals: s orbitals are spherical, p orbitals are dumbbell-shaped, d orbitals are more complex, and f orbitals are intricate.
- 44
Energy levels
Energy levels in an atom are quantized regions where electrons can exist, with each level corresponding to a specific principal quantum number.
- 45
Emission spectra
Emission spectra are the specific wavelengths of light emitted by excited atoms as electrons return to lower energy levels.
- 46
Absorption spectra
Absorption spectra show the wavelengths of light absorbed by atoms when electrons jump to higher energy levels.
- 47
Rydberg formula
The Rydberg formula calculates the wavelengths of spectral lines in hydrogen by relating them to the energy differences between electron levels.
- 48
Planck's constant
Planck's constant is a fundamental constant that relates the energy of a photon to its frequency, equal to approximately 6.626 × 10^-34 joule-seconds.
- 49
Threshold frequency
Threshold frequency is the minimum frequency of light required to eject electrons from a metal surface in the photoelectric effect.
- 50
Work function
The work function is the minimum energy needed to remove an electron from the surface of a metal.
- 51
Line spectra
Line spectra are patterns of distinct lines of color produced when atoms emit or absorb light at specific wavelengths.
- 52
Balmer series
The Balmer series is a set of spectral lines in the visible region produced by electrons in hydrogen transitioning to the n=2 energy level.
- 53
Lyman series
The Lyman series consists of ultraviolet spectral lines from hydrogen, resulting from electrons falling to the n=1 energy level.
- 54
Paschen series
The Paschen series is a group of infrared spectral lines from hydrogen, occurring when electrons transition to the n=3 energy level.
- 55
Nuclear fission
Nuclear fission is the process where a heavy nucleus splits into smaller nuclei, releasing energy, as seen in atomic bombs and nuclear reactors.
- 56
Nuclear fusion
Nuclear fusion is the combining of two light nuclei to form a heavier nucleus, releasing energy, and is the process powering the sun.
- 57
Electron configuration of carbon
The electron configuration of carbon, with atomic number 6, is 1s² 2s² 2p², meaning two electrons in the 1s orbital, two in the 2s, and two in the 2p.
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Ionization energy
Ionization energy is the energy required to remove an electron from a gaseous atom or ion, and it increases across a period in the periodic table.
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Electronegativity
Electronegativity is a measure of an atom's ability to attract electrons in a chemical bond, influenced by its atomic structure.
- 60
Quantum numbers for an electron
Quantum numbers for an electron include n for energy level, l for orbital shape, ml for orientation, and ms for spin, uniquely identifying its state.
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Common trap: Electron spin
A common error is thinking electron spin is like a planet spinning; it is actually an intrinsic quantum property with two possible values.
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Periodic trends in atomic size
Atomic size decreases across a period due to increasing effective nuclear charge and increases down a group due to additional electron shells.