Chapter 2: Life's Chemical Basis

Vocabulary flashcards covering the key terms and concepts from Chapter 2: Life's Chemical Basis.

Mercury

A naturally occurring toxic metal released into the atmosphere by volcanic activity and burning coal that combines with carbon to form methylmercury.

Methylmercury

A toxic compound formed when mercury combines with carbon, which ends up in the tissues of aquatic organisms and in large amounts in large predatory fish.

Charge

An electrical property where like charges repel and opposite charges attract.

Atomic number

The number of protons in the nucleus of an atom, which determines the type of atom, or element.

Elements

Pure substances that consist only of atoms with the same atomic number.

Periodic table

An arrangement of the elements by atomic number, invented by Dmitry Mendeleyev.

Isotopes

Atoms of an element that differ in their number of neutrons.

Mass number

The total number of neutrons and protons in the nucleus of an isotope.

Radioisotope

A radioactive isotope with an unstable nucleus that breaks up spontaneously and emits radiation.

Tracers

Substances with a detectable component, such as radioisotopes, widely used in research and medical applications.

PET (positron-emission tomography)

A medical application of radioisotopes that allows viewing a process within a person's body using a radioactive sugar or other tracer.

Free radicals

Atoms with unpaired electrons that are very unstable and dangerous to life.

Ions

Atoms with an unequal number of protons and electrons that carry a net positive or negative charge.

Chemical bond

An attractive force arising between two atoms when their electrons interact.

Molecule

A structure formed when atoms interact and are held together by chemical bonds.

Compound

A molecule consisting of two or more elements.

Ionic bond

A chemical bond in which atoms are held together by mutual attraction of opposite charges.

Polarity

The separation of charge.

Electronegativity

A measure of an atom's tendency to pull electrons away from another atom.

Covalent bond

A chemical bond formed when electrons from different atoms share a space in an electron shell.

Hydrogen bond

An attraction between a covalently bonded hydrogen atom and another atom taking part in a separate polar covalent bond.

Hydrophilic

Water-loving; describes substances that dissolve easily in water.

Solution

A uniform mixture of substances, such as salt dissolved in water.

Concentration

The amount of solute dissolved in a given amount of fluid.

Hydrophobic

Water-dreading; describes substances, such as oils, that do not interact with water.

Cohesion

The property of water where hydrogen bonds collectively exert a continuous pull on individual water molecules, playing a role in surface tension.

Evaporation

The process by which water molecules escape from a liquid water surface as vapor.

Temperature

A measure of the energy of motion of atoms and molecules.

pH

A measure of the number of hydrogen ions in a water-based fluid.

Acids

Substances that give up hydrogen ions in water and have a pH below 7.

Bases

Substances that accept hydrogen ions from water and have a pH above 7.

Buffer

A set of chemicals, such as carbonic acid ($\text{H}_2\text{CO}_3$) and bicarbonate ($\text{HCO}_3^-$), that act to keep pH stable.