Chapter 02 Atoms, Ions, and Molecules

A vocabulary-focused set of flashcards covering the key terms and concepts from Chapter 2 notes on atoms, ions, molecules, and basic biochemistry.

Matter

Substance that has mass and occupies space; exists in solid, liquid, or gas forms.

Atom

Smallest particle that exhibits the chemical properties of an element.

Element

Fundamental substance composed of atoms with the same atomic number; 92 naturally occurring elements.

Periodic Table

Organization of elements by atomic number and properties.

Proton

Positively charged subatomic particle in the nucleus; mass ~1 amu; +1 charge.

Neutron

Electrically neutral subatomic particle in the nucleus; mass ~1 amu; no charge.

Electron

Negatively charged subatomic particle; very light; located in electron orbitals.

Atomic Number

Number of protons in an atom; shown above the element symbol.

Mass Number

Total number of protons and neutrons in the nucleus.

Isotopes

Atoms of the same element with the same protons but different neutrons; different atomic masses.

Radioisotopes

Unstable isotopes that emit radiation as they decay to a stable form.

Half-life (physical)

Time required for 50% of a radioisotope to decay.

Biological Half-life

Time required for half of a radioactive substance to be eliminated from the body.

Ions

Atoms with a net charge due to loss or gain of electrons (cations or anions).

Cations

Positively charged ions formed when an atom loses electrons.

Anions

Negatively charged ions formed when an atom gains electrons.

Ionic Bond

Electrostatic attraction between oppositely charged ions in a lattice (salts).

Covalent Bond

Chemical bond formed by sharing electrons between atoms.

Single Covalent Bond

One pair of electrons shared between atoms.

Double Covalent Bond

Two pairs of electrons shared between atoms.

Triple Covalent Bond

Three pairs of electrons shared between atoms.

Molecule

Two or more atoms held together by covalent bonds.

Molecular Formula

Notation that shows the number and type of atoms in a molecule.

Structural Formula

Diagram showing the arrangement of atoms and bonds in a molecule.

Isomer

Compounds with the same molecular formula but different structures.

Valence Shell

Outermost electron shell; determines bonding behavior.

Octet Rule

Atoms gain, lose, or share electrons to achieve eight electrons in the outer shell.

Noble Gases

Inert elements with full outer shells (chemically stable).

Electronegativity

Atom’s tendency to attract electrons in a bond; increases across a period and up a group.

Polar Covalent Bond

Covalent bond with unequal sharing of electrons, creating partial charges.

Nonpolar Covalent Bond

Covalent bond with equal sharing of electrons.

Amphipathic

Molecule with both polar (water-loving) and nonpolar regions.

Hydrogen Bond

Weak intermolecular attraction between a partially positive H and a negatively charged atom.

Intermolecular Attractions

Weak forces between molecules, including hydrogen bonds and dipole interactions.

Cohesion

Attraction between water molecules due to hydrogen bonding.

Adhesion

Attraction between water molecules and other substances.

Surface Tension

Inward pulling of cohesive forces at a liquid surface.

Water’s High Specific Heat

Water requires a lot of energy to change temperature, stabilizing body temperature.

Heat of Vaporization

Energy required to convert a liquid to a gas; high for water.

Universal Solvent

Water dissolves many substances, especially polar molecules and ions.

Hydration Shell

Water molecules surrounding dissolved ions or polar solutes.

Hydrophilic

Substances that dissolve readily in water.

Hydrophobic

Substances that do not dissolve in water; water-fearing.

Suspension

Mixture where larger particles are dispersed but may settle out; not evenly mixed.

Colloid

Mixture with smaller particles that do not settle; remains mixed.

Solution

Homogeneous mixture where solute is dissolved in solvent; light passes through.

Emulsion

Emulsified mixture of water and a nonpolar liquid stabilized by agitation.

Concentration (Mass/Volume)

Mass of solute per volume of solution.

Concentration (Mass/Volume Percent)

Grams of solute per 100 mL solution.

Molarity

Moles of solute per liter of solution; temperature dependent.

Molality

Moles of solute per kilogram of solvent; temperature independent.

Osmoles (osm)

Unit of particle concentration in solution; indicates dissociation.

Osmolarity

Number of particles per liter of solution.

Osmolality

Number of particles per kilogram of water.

Mole

Amount of substance containing 6.022×10^23 entities; mass equals molar mass in grams.

Dehydration Synthesis (Condensation)

Chemical reaction where monomers join and a water molecule is released.

Hydrolysis

Bond breaks with addition of water, yielding monomers.

Carbohydrates

Biomolecule class built from monosaccharides; general formula (CH2O)n.

Monosaccharide

Simple sugar monomer (e.g., glucose, fructose, galactose).

Disaccharide

Two monosaccharides linked (e.g., sucrose, lactose, maltose).

Polysaccharide

Many monosaccharides linked (e.g., glycogen, starch, cellulose).

Glycogen

Storage form of glucose in liver and muscle.

Hexose

Six-carbon sugar (e.g., glucose, galactose, fructose).

Pentose

Five-carbon sugar (e.g., ribose, deoxyribose).

Nucleic Acids

DNA and RNA; store and transfer genetic information.

Nucleotide

Monomer of nucleic acids comprised of sugar, phosphate, and base.

Phosphodiester Bond

Covalent bond linking nucleotides in DNA/RNA.

DNA

Deoxyribonucleic acid; double-stranded; stores genetic information.

RNA

Ribonucleic acid; usually single-stranded; involved in protein synthesis.

ATP

Adenosine triphosphate; energy currency of the cell; three phosphates.

Amino Acids

Monomers of proteins; 20 types with an amino group, carboxyl group, and R group.

Peptide Bond

Covalent bond linking amino acids during dehydration synthesis.

Protein Structure (Levels)

Primary, secondary, tertiary, and quaternary structures. Primary = sequence; secondary = alpha helix/beta sheet; tertiary = 3D folding; quaternary = multiple polypeptides.

Denaturation

Loss of protein structure and function due to heat, pH, or chemicals.