Chapter 2: The Nature of Molecules and the Properties of Water

Flashcards covering definitions and explanations of key terms related to the nature of molecules and the properties of water.

Atom

The basic unit of a chemical element, composed of protons, neutrons, and electrons.

Protons

Subatomic particles within an atom's nucleus that have a positive charge.

Neutrons

Subatomic particles within an atom's nucleus that have no charge.

Electrons

Negatively charged subatomic particles that orbit the nucleus of an atom.

Electron shells

The energy levels where electrons are found surrounding the nucleus.

Valence shell

The outermost shell of electrons that determines an atom's chemical properties.

Isotopes

Atoms of the same element that have different numbers of neutrons.

Decay

The process by which an unstable atomic nucleus loses energy by radiation.

Radiation

Energy emitted in the form of waves or particles.

Radioisotopes

Isotopes that undergo radioactive decay and emit radiation.

Radioactivity

The spontaneous emission of radiation from certain unstable atomic nuclei.

Ionizing radiation

Radiation that carries enough energy to liberate electrons from atoms or molecules.

Mutagenic

Substances that can cause changes in the DNA of organisms.

Carcinogenic

Substances capable of causing cancer in living tissue.

Half-life

The time required for half of the quantity of a radioactive isotope to decay.

Physical half-life

The time required for a radioactive substance to reduce to half its initial value due solely to physical decay.

Biological half-life

The time it takes for a substance to be reduced by half in a biological system.

Elements

Pure substances that cannot be broken down into simpler substances by chemical means.

Atomic number

The number of protons in the nucleus of an atom, which defines the element.

Trace elements

Elements required by living organisms in minute quantities.

Molecules

Two or more atoms bonded together, representing the smallest fundamental unit of a chemical compound.

Compounds

Substances formed when two or more elements are chemically bonded together.

Molecular formulas

Notations that indicate the types and numbers of atoms in a molecule.

Chemical bonds

Forces that hold atoms together in molecules.

Ionic bonds

Chemical bonds formed through the electrical attraction between oppositely charged ions.

Covalent bonds

Bonds formed when two atoms share one or more pairs of electrons.

Hydrogen bonds

Weak attractions that occur between hydrogen atoms and electronegative atoms.

Van der Waals forces

Weak intermolecular forces that occur between molecules.

Nonpolar covalent bond

A type of bond where two atoms share electrons equally.

Polar covalent bond

A bond in which electrons are shared unequally between two atoms.

Protein folding

The process by which a protein assumes its functional shape or conformation.

Chemical reactions

Processes that involve the rearrangement of molecular or ionic structure of substances.

Mixtures

Combinations of two or more substances where each retains its properties.

Solvency

The ability of a solvent to dissolve a solute.

Hydrophilic

Substances that are attracted to water.

Hydrophobic

Substances that repel water.

Adhesion

The tendency of dissimilar particles or surfaces to cling to one another.

Cohesion

The tendency of similar or identical particles or surfaces to cling to each other.

Surface film

A thin layer at the surface of a liquid that behaves like an elastic membrane.

Surface tension

The energy required to increase the surface area of a liquid due to intermolecular forces.

Chemical reactivity

The tendency of a substance to undergo chemical reactions.

Thermal stability

The ability of a molecule to remain intact at high temperatures.

Heat capacity

The amount of heat energy required to change the temperature of a substance.

Acid

A substance that increases the concentration of hydrogen ions in a solution.

Base

A substance that decreases the concentration of hydrogen ions in a solution.

pH

A measure of how acidic or basic a solution is, on a scale of 0 to 14.

Buffers

Substances that minimize changes in pH when acids or bases are added.