Chapter 02: Atoms, Ions, and Molecules

Vocabulary practice flashcards covering fundamental chemistry, subatomic structure, chemical bonds, reactions, inorganic molecules, and major biological macromolecules from Chapter 02.

Matter

Anything that has mass and occupies space, existing in solid, liquid, or gas forms.

Kinetic energy

The form of energy associated with matter in motion.

Potential energy

Stored energy that has the capacity to do work or be converted into active energy.

Proton

A subatomic particle in the atomic nucleus with a mass of $1\,\text{amu}$ and a positive charge of $+1$.

Neutron

A subatomic particle in the atomic nucleus with a mass of $1\,\text{amu}$ and no electrical charge.

Electron

A subatomic particle in electron orbitals surrounding the nucleus with a negative charge of $-1$ and a mass of approximately $\frac{1}{1800}\text{th}$ of a proton or neutron.

Atomic number

The number of protons contained within an atom of a specific element.

Average atomic mass

The combined mass of both protons and neutrons within an atom.

Isotope

Atoms of the same element that share the same number of protons and electrons but differ in their number of neutrons.

Radioisotope

An unstable isotope containing excess neutrons that decays and emits radiation to reach a stable state.

Physical half-life

The duration of time needed for $50\%$ of a radioisotope to decay into a stable isotope.

Biological half-life

The time required for half of a radioactive or nonradioactive material to be eliminated from the human body.

Compound

A specific type of molecule composed of two or more different kinds of atoms bonded together.

Solution

A homogeneous mixture containing solute particles dissolved and evenly distributed throughout a solvent.

Solvent

The substance present in the greatest amount within a solution, typically a liquid like water.

Solute

The substance dissolved in a solvent, present in smaller amounts in a solution.

Colloid

A heterogeneous mixture (also called an emulsion) containing solute particles that scatter light but do not settle out.

Suspension

A heterogeneous mixture containing large solutes that scatter light and settle out of solution if left undisturbed.

Valence shell

An atom's outermost electron shell, holding the electrons involved in chemical bonding.

Octet rule

The rule stating that atoms tend to gain, lose, or share electrons to attain a full outer shell of $8$ electrons.

Ionic bond

A chemical bond resulting from the complete transfer of valence shell electrons between atoms, forming attracted oppositely charged ions.

Cation

A positively charged ion formed when an atom loses one or more valence electrons.

Anion

A negatively charged ion formed when an atom gains one or more valence electrons.

Covalent bond

A chemical bond formed when two atoms share two or more valence shell electrons.

Nonpolar covalent bond

A covalent bond formed by equal sharing of electrons between atoms, resulting in an electrically balanced molecule.

Polar covalent bond

A covalent bond formed by unequal sharing of electrons between atoms due to differences in electronegativity.

Hydrogen bond

A weak attractive magnetic force between an electropositive hydrogen atom of one polar molecule and an electronegative atom of another molecule.

Reactant

A starting chemical substance that enters into a chemical reaction.

Product

The resulting chemical substance generated by a chemical reaction.

Synthesis reaction

A reaction in which atoms or molecules combine to form a larger, more complex molecule (an anabolic process).

Decomposition reaction

A reaction that breaks down a molecule into smaller molecules or constituent atoms (a catabolic process).

Exchange reaction

A reaction involving both synthesis and decomposition where chemical bonds are both made and broken.

Exergonic reaction

A chemical reaction that results in a net release of energy, producing end products with lower potential energy than reactants.

Endergonic reaction

A chemical reaction that requires a net absorption of energy, producing end products with higher potential energy than reactants.

Catalyst

A substance that speeds up the rate of a chemical reaction without undergoing permanent chemical changes or being consumed.

Inorganic compound

A chemical substance lacking carbon, such as water, salts, and most acids and bases.

Electrolyte

An ionic compound that dissociates into ions when dissolved in water and is capable of conducting electrical currents.

Acid

A proton donor that releases hydrogen ions ($\text{H}^+$) in solution.

Base

A proton acceptor that picks up hydrogen ions ($\text{H}^+$) and releases hydroxyl ions ($\text{OH}^-$) in solution.

pH

A logarithmic measure of the hydrogen ion concentration ($[\text{H}^+]$) of a solution, scaled from $0$ to $14$.

Buffer

A chemical substance or system that resists abrupt shifts in pH by binding or releasing free hydrogen ions ($\text{H}^+$).

Organic compound

A carbon-containing, covalently bonded compound unique to living organisms, such as carbohydrates, lipids, proteins, and nucleic acids.

Polymer

A large molecule composed of repeating chains of monomer units.

Dehydration synthesis

A chemical reaction that joins monomers together into polymers by removing a molecule of water.

Hydrolysis

A chemical reaction that breaks polymers down into monomer units through the addition of a water molecule.

Monosaccharide

A simple single-sugar molecule containing $3$ to $7$ carbon atoms that serves as a monomer for carbohydrates.

Disaccharide

A double sugar formed by linking two monosaccharides together via dehydration synthesis.

Polysaccharide

A long carbohydrate polymer formed by joining many monosaccharide monomers through dehydration synthesis.

Glycogen

A polysaccharide that functions as the primary carbohydrate storage molecule in animals.

Triglyceride

A lipid composed of three fatty acid chains attached to a glycerol molecule, used for energy storage, insulation, and protection.

Saturated fatty acid

A fatty acid chain with only single covalent bonds between carbons, containing the maximum possible number of hydrogen atoms.

Unsaturated fatty acid

A fatty acid chain containing one or more double bonds between carbon atoms, resulting in fewer bonded hydrogen atoms.

Phospholipid

A modified lipid containing glycerol, two fatty acids, and a phosphate group, featuring a polar hydrophilic head and nonpolar hydrophobic tails.

Steroid

A lipid molecule characterized by four interlocking hydrocarbon rings, such as cholesterol.

Amino acid

The monomer building block of proteins, consisting of an amine group, a carboxylic acid group, and one of $20$ distinct R groups.

Peptide bond

The covalent bond joining two amino acids together in a polypeptide chain.

Primary structure

The linear sequence of amino acids joined by peptide bonds in a polypeptide chain.

Secondary structure

Local structural arrangements in a protein, such as alpha helices or beta sheets, formed by hydrogen bonding between amino acids.

Tertiary structure

The final overall $3\text{D}$ folding shape of a single protein polypeptide chain.

Quaternary structure

The complex protein shape formed by the interaction and combination of two or more separate polypeptide chains.

Fibrous protein

A strandlike, water-insoluble, stable protein that provides structural support and mechanical strength.

Globular protein

A compact, spherical, water-soluble protein with specific active sites that carries out functional chemical roles.

Denaturation

The process in which globular proteins unfold and lose their functional $3\text{D}$ shape due to changes in pH or temperature.

Enzyme

A globular protein that acts as a biological catalyst to accelerate chemical reactions by lowering activation energy.

Nucleotide

The monomer unit of nucleic acids, consisting of a nitrogenous base, a pentose sugar, and a phosphate group.

DNA (Deoxyribonucleic acid)

A double-stranded helical nucleic acid containing deoxyribose sugar and thymine that stores cellular genetic blueprints.

RNA (Ribonucleic acid)

A single-stranded nucleic acid containing ribose sugar and uracil that carries out DNA instructions for protein synthesis.

ATP (Adenosine triphosphate)

An adenine-containing RNA nucleotide with three phosphate groups that provides usable chemical energy to power cell processes.