Chapter 2: The Nature of Molecules and the Properties of Water-Natalie Rangel

Vocabulary flashcards generated from Chapter 2 lecture notes, covering atomic structure, chemical bonding, water properties, and acids and bases.

Matter

Anything that takes up space and has mass.

Element

A pure substance that cannot be broken down to other substances by chemical reactions.

Atom

The smallest unit of matter that still retains the properties of an element.

Proton

A subatomic particle contained in the nucleus of an atom that carries a positive charge ($+$) and determines the element.

Neutron

A subatomic particle contained in the nucleus of an atom that has a neutral charge (no charge) and determines the isotope.

Electron

A subatomic particle carrying a negative charge ($-$) that orbits the nucleus and determines atomic reactivity.

Atomic Number

The specific number of protons contained in an atom of an element, which identifies the element.

Mass Number

The total number of protons plus neutrons contained in the nucleus of an atom.

Isotope

One of two or more forms of the same element that contain equal numbers of protons but different numbers of neutrons.

Radioactive Isotope

An unstable isotope whose nucleus spontaneously decays or breaks down, emitting particles and energy.

Cation

A positively charged ion formed when an atom has more protons than electrons.

Anion

A negatively charged ion formed when an atom has more electrons than protons.

Potential Energy

Stored energy possessed by matter due to its location or structure, such as electrons situated farther from the nucleus.

Valence Electrons

The electrons occupying the outermost electron shell (valence shell) that govern an atom's chemical behavior and reactivity.

Trace Elements

Chemical elements required by living organisms in minute quantities ($<0.01\%$).

Molecule

Two or more atoms held together by chemical bonds.

Compound

A molecule composed of two or more different elements combined in a fixed ratio.

Covalent Bond

A strong chemical bond formed when two atoms share a pair of valence electrons.

Single Covalent Bond

A covalent bond involving the sharing of one pair ($2$ electrons) of valence electrons between two atoms.

Double Covalent Bond

A covalent bond involving the sharing of two pairs ($4$ electrons) of valence electrons between two atoms.

Triple Covalent Bond

A covalent bond involving the sharing of three pairs ($6$ electrons) of valence electrons between two atoms.

Electronegativity

A measure of an atom's attraction for the shared electrons in a covalent bond.

Polar Covalent Bond

A covalent bond between atoms that differ in electronegativity, leading to unequal sharing of electrons and creating partial charges.

Nonpolar Covalent Bond

A covalent bond in which electrons are shared equally between two atoms of similar electronegativity.

Ion

An atom or molecule that has acquired a net electric charge by gaining or losing one or more electrons.

Ionic Bond

A chemical bond resulting from the electrostatic attraction between oppositely charged ions (a cation and an anion).

Hydrogen Bond

A weak chemical attraction formed when a partially positive hydrogen atom in a polar covalent molecule is attracted to an electronegative atom (such as oxygen or nitrogen) in another polar molecule.

Reactants

The starting materials or molecules present at the beginning of a chemical reaction.

Products

The final substances or molecules formed as a result of a chemical reaction.

Cohesion

The attraction between like molecules, such as hydrogen bonds holding water molecules together.

Adhesion

The attraction between different types of molecules, such as water molecules sticking to plant cell walls.

Surface Tension

A measure of how difficult it is to stretch or break the surface of a liquid, produced by cohesion among surface water molecules.

Specific Heat

The amount of heat that must be absorbed or lost for $1\,g$ of a substance to change its temperature by $1^\circ\text{C}$.

Heat of Vaporization

The quantity of heat energy required to convert a liquid into a gas.

Evaporative Cooling

The reduction in temperature of a surface when liquid evaporates, as the highest-energy molecules escape into the gas phase.

Solvent

The liquid component of a solution in which solutes are dissolved.

Solute

The substance that is dissolved in a solvent to form a solution.

Solution

A liquid that consists of a completely homogeneous mixture of two or more substances.

Aqueous Solution

A solution in which water serves as the solvent.

Hydrophilic

Having an affinity for water; describes polar or charged substances that readily dissolve in water.

Hydrophobic

Lacking an affinity for water; describes nonpolar substances that do not dissolve in water.

Amphipathic Molecules

Molecules that contain both hydrophilic (polar) and hydrophobic (nonpolar) regions.

Acid

A substance that increases the hydrogen ion ($\text{H}^+$) concentration of a solution, corresponding to a pH value from $0$ to $6.9$.

Base

A substance that reduces the hydrogen ion ($\text{H}^+$) concentration of a solution, corresponding to a pH value from $7.1$ to $14$.

pH

A measure of the relative concentration of hydrogen ions ($[\text{H}^+]$) in a solution, defined as $\text{pH} = -\log[\text{H}^+]$.

Buffer

A substance that minimizes changes in pH by absorbing excess hydrogen ions or donating hydrogen ions when depleted.