Chapter 2.txt

[L. acidus, sour] Any water-soluble substance that releases hydrogen ions (H+) in water, yielding a pH below 7.0.

The smallest unit of an element that still retains the element�s properties.

The number of protons in the nucleus of atoms of a given element.

Any water-soluble substance that releases hydroxyl ions in water to yield a pH greater than 7.0. Also the nitrogencontaining component of a nucleotide.

A weak acid and the salt that forms when it dissolves. The two work as a pair to counter slight shifts in pH.

A union between the electron structures of two or more atoms.

A capacity to resist rupturing when placed under tension (stretched).

Molecule consisting of two or more elements in proportions that do not vary, as they can in mixtures.

[L. con, together, + valere, to be strong] A sharing of one or more electrons between two atoms. In a polar covalent bond, the atoms share electrons unequally; in a nonpolar covalent bond, each atom gets an equal share of the electrons.

Negatively charged subatomicparticle. Electrons occupy orbitals around the atomic nucleus.

Fundamental form of matter that cannot be degraded to a simpler form by ordinary means. All atoms of an element have the same atomic number.

Process of conversion of a liquid to a gas; requires energy input.

A weak attraction that has formed between a covalently bonded hydrogen atom and an electronegative atom taking part in another covalent bond.

Free (or unbound) proton; one hydrogen atom that lost its electron and now bears a positive charge (H+).

[Gk. philos, loving] A polar molecule that dissolves easily in water; e.g., glucose.

[Gk. phobos, dreading] A nonpolar molecule that resists dissolving in water; e.g., oil.

Atom having an unequal number ofprotons and electrons; it carries a positive or negative electric charge.

Ions interacting through the attraction of their opposite charges.

One of two or more atoms of the same element (same number of protons) that differ in their number of neutrons.

Sum of protons and neutrons in the nucleus of an element�s atoms.

Two or more types of molecules intermingled in proportions that can and usually do vary.

Two or more covalently bonded atoms of the same or different elements.

Type of subatomic particle in the nucleus of all atoms except hydrogen; has mass but no charge.

Tabular arrangement of elements in order of their increasing atomic number.

Measure of the H+ concentration of a solution. pH 7 is neutral.

Positively charged subatomic particle in the nucleus of all atoms.

Natural, inevitable process by which an atom emits energy as subatomic particles and x-rays as its unstable nucleus spontaneously breaks apart; transforms one element into another in a predictable time span.

Any isotope that has an unstable nucleus.

Any compound that releases ions other than H+ and OH- in solution.

Model for how electrons are distributed in an atom; all of the orbitals are shown as a nested series of shells.

[L. solvere, to loosen] Any substance dissolved in a solution.

Any fluid (e.g., water) in which one or more substances are dissolved.

A clustering of water molecules around molecules or ions of a solute by positive and negative interactions.

Measure of molecular motion.

Any substance with a radioisotope attached; researchers can track it after delivering it into a cell, a multicelled body, ecosystem, or some other system.