The science of the structure and interactions of matter.
Anything that occupies space and has mass.
The amount of matter in any object; never changes.
The building blocks of all forms of matter -- both living and nonliving; cannot be split into a simpler substance by ordinary chemical means.
One or two letters of an element's name in English, Latin, or another language (ex. H for Hydrogen, Ne for Neon, or K for Potassium).
Carbon, Hydrogen, Oxygen, and Nitrogen; they alone make up about 96% of the body's mass.
Carbon, Hydrogen, Oxygen, and Nitrogen
The four major elements in the human body.
Calcium, Phosphorous, Potassium, Sulfur, Sodium, Chlorine, Magnesium, and Iron; make up about 3.6% of the body's mass.
Calcium, Phosphorous, Sulfur, Potassium, Sodium, Chlorine, Magnesium, and Iron
The eight lesser elements in the human body.
The elements that make up the last .4% of the mass of the body.
The smallest units of matter that retain the properties and characteristics of the elements.
The dozens of particles that compose atoms, namely protons, neutrons, and electrons.
The dense central core of an atom where protons and neutrons are located.
Positively charged particles located within the nucleus of an atom.
Uncharged (neutral) particles located within the nucleus of an atom.
Negatively charged particles located in a cloud, moving about the nucleus of an atom.
The regions outside the nucleus that electrons move about in; depicted as simple circles around the nucleus; each region holds a specific number of electrons (2.8.18).
The number of protons in an atom.
The sum of an atom's protons and neutrons.
Atoms of an element that have different numbers of neutrons and therefore different mass numbers; most of them are stable and do not change over time.
radioactive isotopes (radioisotopes)
Unstable isotopes; their nuclei decay into a stable configuration over time, emitting radiation as they do so, and transform into a different element; the time span of the change is anywhere from a fraction of a second to millions of years, depending on the isotope.
The time required for half of the radioactive atoms in a sample of an isotope to decay into a more stable form.
dalton (atomic mass unit)
The standardized unit of measurement for the mass of atoms and their subatomic particles.
atomic mass (atomic weight)
The average mass of all of an atom's naturally occurring isotopes.
An atom that has a positive or negative charge because it has unequal numbers of protons and electrons.
The process of giving up or gaining electrons.
Two or more atoms sharing electrons.
Indicates the elements and the number of atoms of each element that make up a molecule.
A substance that contains atoms of two or more different elements.
An atom or group of atoms with an unpaired electron in the outermost shell; makes the atom unstable, highly reactive, and destructive to nearby molecules.
Substances that inactivate oxygen-derived free radicals.
Radioisotopes used to follow movements of certain substances through the body.