Chapter 2: Matter, Atoms, Elements, and the Periodic Table

Vocabulary-style flashcards covering key terms from matter and atoms, chemical bonds, water and solutions, and biological macromolecules. Each card defines a essential term likely to appear on exams.

Matter

Anything that has mass and occupies space; exists as solid, liquid, or gas.

Atom

The smallest unit of an element that displays its chemical properties.

Element

A substance defined by the number of protons; 92 naturally occurring elements compose matter.

Periodic table

Organization of elements by atomic number and properties.

Proton

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

Neutron

Uncharged subatomic particle in the nucleus; mass ~1 amu.

Electron

Negatively charged subatomic particle orbiting the nucleus; mass ~1/1800 amu.

Atomic number

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

Atomic mass

Mass of protons and neutrons; average mass of the element.

Isotope

Atoms of the same element with same protons/electrons but different neutrons.

Radioisotope

An unstable isotope that emits radiation.

Half-life (physical)

Time required for 50% of a radioisotope to decay.

Biological half-life

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

Ion

Atom with a positive or negative charge from loss or gain of electrons.

Cation

Positively charged ion.

Anion

Negatively charged ion.

Ionic bond

Electrostatic attraction between oppositely charged ions; forms salts.

Salt

Ionic compound formed by cations and anions (e.g., NaCl).

Covalent bond

Atoms share electrons.

Single bond

One pair of electrons shared between atoms.

Double bond

Two pairs of electrons shared.

Triple bond

Three pairs of electrons shared.

Polar covalent bond

Unequal sharing of electrons; creates partial charges.

Nonpolar covalent bond

Equal sharing of electrons; no partial charges.

Electronegativity

Relative attraction of an atom for electrons in a bond.

Octet rule

Atoms tend to achieve eight electrons in the outer shell for stability.

Valence shell

Outermost electron shell involved in bonding.

Electron shell

Concentric energy levels around the nucleus that hold electrons.

Isomer

Molecules with the same formula but different arrangement.

Hydration shell

Water surrounding and stabilizing dissolved particles.

Hydrophilic

Water-loving; substances that readily dissolve in water.

Hydrophobic

Water-fearing; nonpolar substances that do not mix with water.

Amphipathic

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

Intermolecular attractions

Weak forces between molecules (e.g., hydrogen bonds) that influence structure.

Hydrogen bond

Weak bond between a partially positive H and a partially negative atom in another molecule.

Cohesion

Attraction between water molecules due to hydrogen bonding.

Adhesion

Attraction between water molecules and other substances.

Surface tension

Inward pull at the surface of a liquid due to cohesive forces.

High specific heat

Water's ability to resist temperature change due to hydrogen bonding.

High heat of vaporization

Large energy required to convert water from liquid to gas.

Universal solvent

Water; dissolves most substances in the body.

Electrolyte

Substance that dissociates into ions and conducts electricity.

Nonelectrolyte

Substance that does not dissociate into ions and does not conduct.

pH

Measure of hydrogen ion concentration; ranges 0–14 with 7 neutral.

Acid

Dissociates to release H+ in solution (proton donor).

Base

Accepts H+ in solution (proton acceptor).

Buffer

Substance that resists pH changes by neutralizing added acid/base.

Neutralization

Acids and bases react to form a neutral pH, often near 7.

Osmolarity

Number of particles in 1 liter of solution.

Osmolality

Number of particles in 1 kg of solvent.

Molarity

Moles of solute per liter of solution; temperature dependent.

Molality

Moles of solute per kilogram of solvent; temperature independent.

Osmole

Unit representing the number of particles in a solution.

Suspension

Mixture with large particles that settle; appears cloudy.

Colloid

Mixture with intermediate-sized particles that remain suspended.

Solution

Homogeneous mixture where solute is dissolved; transparent.

Emulsion

Colloid of water and nonpolar liquid; forms only when shaken.

Dehydration synthesis

Two subunits join; water is produced.

Hydrolysis

Water splits bonds to break molecules apart.

Monosaccharide

A simple sugar; monomer of carbohydrates.

Disaccharide

Two monosaccharides joined together.

Polysaccharide

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

Glycogen

Storage form of glucose in liver and muscle.

Glucose

Six-carbon sugar; primary energy source for cells.

Nucleotide

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

DNA

Deoxyribonucleic acid; double-stranded; stores genetic information.

RNA

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

ATP

Adenosine triphosphate; energy currency of the cell.

Amino acid

Monomer of proteins; contains an amine, carboxyl, and R group.

Peptide bond

Covalent bond linking amino acids during dehydration synthesis.

Primary structure

Linear sequence of amino acids in a protein.

Secondary structure

Localized patterns (alpha helix or beta sheet) in proteins.

Tertiary structure

Three-dimensional folding of a single polypeptide.

Quaternary structure

Protein with two or more polypeptide chains.

Denaturation

Loss of protein shape and function due to heat or pH changes.

Chaperone

Protein that assists in proper protein folding.

Glycoprotein

Protein with carbohydrate attached; involved in cell recognition.

Proline

Amino acid that can introduce bends in a protein chain.

Cysteine

Amino acid that can form disulfide bonds, stabilizing structure.

Glycosaminoglycans (GAGs)

Large carbohydrates that attach to proteins to form proteoglycans in connective tissue.

Proteoglycan

Proteins with attached glycosaminoglycans in connective tissue.

Phospholipid

Amphipathic lipid with polar head and nonpolar tails; forms cell membranes.

Triglyceride

Three fatty acids attached to glycerol; major energy storage lipid.

Phospholipid bilayer

Double layer of phospholipids forming cell membranes with hydrophilic heads and hydrophobic tails.

Steroid

Hydrocarbon rings (cholesterol, hormones) forming lipids with a four-ring structure.

Eicosanoid

Signaling lipids derived from arachidonic acid; include prostaglandins.

Glycogen

Stored form of glucose in liver and muscle tissue.