Chemistry Chapter 1: Atomic Structure and Periodic Trends Flashcards
Principle Quantum Number (n) definition, possible values and role
Defines: The energy level (or shell) of the electron.
Possible Values: Positive integers (
n=1,2,3,…).
Role:
Indicates the size and energy of the orbital.
Higher n values correspond to higher energy levels and larger orbitals.
Azimuthal (Angular Momentum) Quantum Number (l) definition, possible values and role
Defines: The shape of the orbital (subshell).
Possible Values: Integers ranging from 0 to (n-1).
l = 0: s-orbital (spherical)
l = 1: p-orbital (dumbbell-shaped)
l = 2: d-orbital (clover-shaped)
l = 3: f-orbital (complex shape)
Role: Describes the orbital’s shape and determines its subshell.
Magnetic Quantum Number (ml)
Defines: The orientation of the orbital in space.
Possible Values: Integers ranging from -l to +l, including 0.
Example: If l = 1 (p-orbital), then ml = -1, 0, +1, corresponding to the three p-orbital orientations (px, py, pz).
Role: Specifies the number of orbitals and their orientations within a subshell.
Spin Quantum Number (ms)
Defines: The spin of the electron.
Possible Values: +1/2 (spin-up) or -1/2 (spin-down).
Role: Describes the intrinsic angular momentum (spin) of the electron.
Hund’s Rule
electrons fill degenerate (two or more orbitals have the same energy level) orbitals singly with parallel spins before pairing up, to minimize electron repulsion and maximize stability.
degenerate in physics/chem = have the same energy
Aufbau’s rule
Electrons fill atomic orbitals in order of increasing energy, starting from the lowest energy level before moving to higher ones.
Pauli exclusion principle
states that no two electrons in the same atom can have the same set of all four quantum numbers (n, l, ml, ms), meaning each electron in an atom must occupy a unique quantum state.
Ionization energies are dependent on
Atomic radius.
As atomic radius increases, it is easier to remove an electron because it’s further from the nucleus.
Ionization Energy
is the quantity of energy that an isolated, gaseous atom in the ground electronic state must absorb to discharge an electron, resulting in a cation.
Shielding
When the positive charges on the nucleus are blocked by the middle shells of electrons
Electronegativity
Electronegativity can be understood as a chemical property describing an atom’s ability to attract and bind with electrons. Because electronegativity is a qualitative property, there is no standardized method for calculating electronegativity.
Electron Affinity
electron affinity is the ability of an atom to accept an electron. Unlike electronegativity, electron affinity is a quantitative measurement of the energy change that occurs when an electron is added to a neutral gas atom. The more negative the electron affinity value, the higher an atom’s affinity for electrons.
Why is allene (H2C=C=CH2) linear but twisted?
✅ C₂ (sp hybridized) has two unhybridized p orbitals, which are perpendicular.
✅ C₁ and C₃ (sp² hybridized) each have one unhybridized p orbital.
✅ The unhybridized p orbitals on C₁ and C₃ overlap with the two p orbitals on C₂, forming two perpendicular π bonds.
✅ Allene has a linear geometry at C₂, but the π bonds create a twisted molecular shape.
