Chapter 02 Atoms, Ions, and Molecules – Vocabulary Flashcards

Vocabulary flashcards covering key terms from Chapter 02: Atoms, Ions, and Molecules, including matter, atomic structure, bonds, water, mixtures, and biological macromolecules.

Matter

Anything that has mass and occupies space.

Solid

A form of matter with a definite shape and volume (e.g., bone).

Atom

The smallest unit of a chemical element that retains its properties.

Element

A pure substance consisting of only one type of atom; 92 naturally occurring elements.

Periodic Table

A tabular arrangement of elements organized by atomic number and properties.

Atomic number

The number of protons in the nucleus; shown above the element symbol.

Mass number

Total number of protons and neutrons in the nucleus.

Atomic mass unit (amu)

A standard unit used to express atomic and subatomic particle masses.

Neutron

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

Proton

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

Electron

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

Nucleus

Center of the atom containing protons and neutrons.

Electron shells (orbitals)

Energy levels surrounding the nucleus where electrons reside.

Isotopes

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

Carbon-12

An isotope of carbon with 6 protons and 6 neutrons.

Carbon-13

An isotope of carbon with 6 protons and 7 neutrons.

Carbon-14

An isotope of carbon with 6 protons and 8 neutrons.

Radioisotope

An isotope that is radioactive and releases radiation as it decays.

Half-life (physical)

Time required for 50% of a radioactive sample to decay.

Biological half-life

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

Ion

Atom with a net electrical charge due to loss or gain of electrons.

Cation

Positively charged ion (loss of electrons).

Anion

Negatively charged ion (gain of electrons).

Polyatomic ion

An ion composed of more than one atom.

Ionic bond

Electrostatic attraction between cations and anions; forms salts.

Salt

Ionic compound formed by ionic bonds (e.g., NaCl).

Ionic compound

Compound composed of ions held together by ionic bonds.

Covalent bond

Bond formed by sharing electron pairs between atoms.

Molecule

Two or more atoms held together by covalent bonds.

Molecular formula

Indicates the number and type of atoms in a molecule.

Structural formula

Shows arrangement of atoms and bonds in a molecule.

Isomer

Compounds with the same formula but different arrangement, leading to different properties.

Polar covalent bond

Covalent bond with unequal electron sharing, creating partial charges.

Nonpolar covalent bond

Covalent bond with equal electron sharing; no partial charges.

Electronegativity

Attraction of electrons in a bond; increases across periods and up groups.

Amphipathic

Molecule having both polar (hydrophilic) and nonpolar (hydrophobic) regions.

Hydrogen bond

Weak attraction between a partial positive H and a partial negative atom; key in water and biomolecules.

Intermolecular attractions

Weak bonds between molecules; include hydrogen bonds and hydrophobic interactions.

Water

Polar molecule (H2O) with strong hydrogen bonding; central to many properties of life.

Hydration shell

Layer of water molecules surrounding a dissolved ion or molecule.

Hydrophilic

Water-loving; substances that dissolve in water.

Hydrophobic

Water-fearing; substances that do not dissolve in water.

Electrolyte

Substance that dissociates into ions in solution and conducts electricity.

Nonelectrolyte

Substance that does not dissociate into ions in solution.

pH

Measure of hydrogen ion concentration in solution; scale 0-14.

Acid

Substance that donates H+ ions in water (proton donor).

Base

Substance that accepts H+ ions in water (proton acceptor).

Buffer

Substance that resists pH changes by accepting or donating H+.

Neutralization

Acid-base reaction that returns a solution toward pH 7.

Mixture

Substances mixed without chemical bonding; can be separated by physical means.

Suspension

Mixture with large particles that settle; cloudy.

Colloid

Mixture with particles intermediate in size that remain dispersed; scatters light.

Solution

Homogeneous mixture where solute is dissolved; does not scatter light.

Emulsion

A colloid-like mixture of water and a nonpolar liquid stabilized by emulsifiers.

Osmolarity

Number of particles in a 1-liter solution.

Osmolality

Number of particles in 1 kg of water; more accurate but harder to measure.

Molarity

Moles of solute per liter of solution.

Molality

Moles of solute per kilogram of solvent.

Macromolecule

Large organic molecule; carbohydrates, lipids, proteins, nucleic acids.

Monomer

Subunit that links to form polymers.

Polymer

Large molecule made of repeating monomer units.

Dehydration synthesis

Bond-forming reaction that releases water when monomers join.

Hydrolysis

Bond-breaking reaction that uses water to separate monomers.

Carbohydrate

Macromolecule made of sugar units; CH2O; includes monosaccharides, disaccharides, polysaccharides.

Monosaccharide

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

Disaccharide

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

Polysaccharide

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

Glucose

Six-carbon monosaccharide; primary cellular energy source.

Glycogen

Storage form of glucose in liver and muscle.

Nucleic acids

DNA and RNA; store and transfer genetic information.

Nucleotide

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

Purine

Two-ring bases (A and G).

Pyrimidine

Single-ring bases (C, U, T).

DNA

Double-stranded nucleic acid with deoxyribose; A-T and G-C base pairing; located in nucleus.

RNA

Single-stranded nucleic acid with ribose; A, U, C, G; no thymine.

ATP

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

Amino acid

Monomer of protein; amino group, carboxyl group, hydrogen, and R group.

Peptide bond

Covalent bond formed between amino acids via dehydration synthesis.

Primary structure

Linear sequence of amino acids in a protein.

Secondary structure

Patterned folding (alpha helix, beta sheet) stabilized by hydrogen bonds.

Tertiary structure

Three-dimensional folding of a single polypeptide; globular or fibrous.

Quaternary structure

Protein structure consisting of two or more polypeptide chains.

Denaturation

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

Lipids

Diverse nonpolar, water-insoluble molecules: triglycerides, phospholipids, steroids, eicosanoids.

Triglycerides

Glycerol + three fatty acids; energy storage.

Phospholipids

Amphipathic lipids forming cell membranes; glycerol backbone, phosphate head, fatty acid tails.

Steroids

Lipids with four fused rings; cholesterol, hormones, bile salts.

Eicosanoids

20-carbon fatty acids; local signaling molecules like prostaglandins.

Glycolipids

Lipids with attached carbohydrate found in plasma membranes.

Glycosaminoglycans (GAGs)

Large carbohydrates attached to proteins to form proteoglycans in connective tissue.