Lecture 2 Vocab

Electron

A negatively charged subatomic particle that orbits the nucleus of an atom.

Neutron

A neutral subatomic particle found in the nucleus of an atom.

Proton

A positively charged subatomic particle found in the nucleus of an atom.

Nucleus

The central region of an atom that contains protons and neutrons.

Orbital(s)

Regions around the nucleus where electrons are most likely to be found.

Valence electron

An electron in the outermost shell of an atom; important in bond formation.

Electronegativity

A measure of an atom’s ability to attract shared electrons in a bond.

Aufbau principle

The rule that electrons fill lower-energy orbitals before higher-energy orbitals.

Covalent bond

A strong bond formed when two atoms share one or more pairs of electrons.

Nonpolar covalent

A covalent bond in which electrons are shared equally between atoms.

Polar covalent

A covalent bond in which electrons are shared unequally, creating partial charges.

Ionic bond

A bond formed between oppositely charged ions due to transfer of electrons.

Strong bond

Stable interactions such as covalent bonds; require high energy to break.

Weak bond

Interactions such as hydrogen bonds, ionic bonds in water, hydrophobic interactions, and van der Waals forces; easily reversible.

Hydrogen bond

A weak interaction between a hydrogen atom covalently bonded to an electronegative atom and another electronegative atom.

Hydrogen bond donor

The atom (usually O or N) covalently bonded to hydrogen and capable of donating it in a hydrogen bond.

Hydrogen bond acceptor

The electronegative atom with a lone pair that can accept a hydrogen bond.

van der Waals interaction

Weak, transient attractions between molecules due to temporary dipoles.

Induced dipole

A temporary shift in electron distribution in a molecule caused by a nearby charge.

Acid

A substance that increases the hydrogen ion (H⁺) concentration in a solution.

Base

A substance that decreases hydrogen ion concentration or increases hydroxide ions (OH⁻) in a solution.

Neutral

Describes a solution with equal concentrations of H⁺ and OH⁻ (pH 7).

Autohydration

Also called autoionization; the process where water molecules dissociate into H⁺ (H₃O⁺) and OH⁻ ions.

pH

A scale measuring the concentration of H⁺ in a solution; lower pH = more acidic.

pOH

A scale measuring the concentration of OH⁻ in a solution; lower pOH = more basic.

Cohesion

The property of water molecules sticking to each other due to hydrogen bonding.

Heat capacity

The amount of heat required to raise the temperature of a substance; water has high heat capacity due to hydrogen bonding.

Hydrophilic

"Water-loving"; molecules that readily dissolve in or interact with water.

Hydrophobic

"Water-fearing"; molecules that do not dissolve in water, often nonpolar.

Hydrophobic interaction

The tendency of nonpolar molecules to cluster together in aqueous solutions to minimize water contact.

Amphipathic

A molecule with both hydrophilic (polar) and hydrophobic (nonpolar) regions.

Micell

A spherical structure formed by amphipathic molecules in water, with hydrophobic tails inward and hydrophilic heads outward.

Membrane

A bilayer structure made of amphipathic phospholipids that forms the boundary of cells and organelles.

Water of hydration

Water molecules that are bound to ions or molecules in solution, stabilizing them.

Dipole moment

A measure of the separation of positive and negative charges in a molecule; indicates polarity.

VSEPR

Valence Shell Electron Pair Repulsion theory; predicts molecular shapes based on repulsion between electron pairs.