Organic Chemistry I: Electronic Structure & Bonding

This flashcard set covers key concepts from the lecture on Electronic Structure & Bonding in Organic Chemistry, including atomic structure, quantum mechanics, bonding theories, and resonance.

What is the definition of Atomic Number (Z)?

It is the number of protons in an atom's nucleus.

What does Mass Number (A) represent?

It is the total number of protons and neutrons in the nucleus.

What are Isotopes?

Atoms of the same element with varying numbers of neutrons and different mass numbers.

How is Atomic Mass defined?

The weighted average mass in atomic mass units (amu) of an element’s naturally occurring isotopes.

What is Quantum Mechanics in the context of atomic structure?

It describes the characteristics of electrons in atoms including the four quantum numbers.

What does the Principal Quantum Number (n) indicate?

It denotes the size and energy level of an electron shell.

What is the Angular Momentum Quantum Number (ℓ) and its significance?

It indicates the shape of the orbital.

What does the Magnetic Quantum Number (mℓ) define?

It defines the orientation of the orbital.

What is the Electron Spin Quantum Number (ms)?

It determines the orientation of the electron spin.

What is an Atomic Orbital?

Regions where electrons reside, characterized by their wave function.

What is the Aufbau principle?

Orbitals fill from lowest energy to highest.

What does the Pauli Exclusion Principle state?

A maximum of two electrons can occupy the same orbital with opposite spins.

What is Hund's Rule?

Degenerate orbitals fill singly before pairing.

What is the significance of the Electron Octet configuration?

It indicates a stable configuration of eight valence electrons.

What are Ionic Bonds?

Bonds formed by electron transfer between metals and nonmetals.

What are Covalent Bonds?

Bonds formed by electron sharing between non-metals.

How does Electronegativity change across the periodic table?

It increases across periods.

What is the Inductive Effect?

The shifting of electrons in a bond due to nearby electronegative atoms.

What does a Dipole Moment measure?

It measures charge separation in polar covalent bonds.

What is a Lewis Structure?

A representation of a molecule indicating the arrangement of electrons.

What does Formal Charge represent?

It indicates the charge of an atom in a molecule based on its valence electrons.

What are typical bonding numbers for Carbon and Oxygen?

Carbon is tetravalent, Oxygen is divalent.

What is VSEPR Theory?

A theory that predicts molecular geometry based on electron pair repulsion.

What does AXE notation represent?

A represents the central atom, X the number of bonded atoms, and E the number of lone pairs.

What does Hybridization involve?

A process of mixing atomic orbitals to form new hybrid orbitals.

What is Resonance in chemistry?

A phenomenon where multiple valid Lewis structures can describe the same molecule.

What does Stability and Resonance Energy indicate?

Resonance hybrids are generally lower in energy and more stable than any single resonance form.

What is a Two-Center System in regards to bonds?

A system where a pi bond sits between two atoms with different electronegativities.

What is the difference between Localized and Delocalized Electrons?

Localized electrons are stuck in place, while delocalized electrons can move around the molecule.

What changes between resonance structures?

Only electrons (specifically pi electrons and lone pairs) move; the position of atoms and sigma bonds remains constant.

What is a key requirement for all resonance structures?

Each resonance structure must be a valid Lewis structure, adhering to rules like the octet rule (or expanded octet for elements in period 3 and beyond) and showing correct formal charges.

What characteristics make a resonance structure a major contributor to the overall resonance hybrid?

Major contributors typically have more covalent bonds, fewer formal charges, and any negative formal charges are located on more electronegative atoms.

How does the overall charge of a molecule relate between its resonance structures?

The overall net charge of the molecule must remain the same in all valid resonance structures.

What is the relationship between individual resonance structures and the actual molecule?

Individual resonance structures are not real, equilibrium forms; they are hypothetical contributors to a single, real resonance hybrid that exists as an average of all valid forms.

What types of electron movements are permissible when drawing resonance structures?

Allowed electron movements involve primarily pi electrons and lone pairs, typically moving from a lone pair to form a pi bond, from a pi bond to form another pi bond, or from a pi bond to become a lone pair.