law of conservation of mass
mass is neither created nor destroyed.
law of definite proportion
a given compound always contains exactly the same proportion of elements by mass.
law of multiple proportions
a law stating that when two elemts form a series of compounds, the ratios of the masses of the second element that combine with one gram of the first element can always be reduced to small whole numbers.
atomic masses
the weighted averages of isotopes
atomic weights
the weighted average mass of the atoms in a naturally occuring element.
Avogadro's hypothesis
equal volumes of gases at the same temperature and pressure contain equal numbers of particles
cathode-ray tubes
the "rays" emanating from the negative electrode in a partially evacuated tube; a stream of electrons.
electrons
negatively charged particles
radioactivity
the spontaneous emission of a stream of particles or electromagnetic rays in nuclear decay
nuclear atom
an atom having a dense center of positive charge (the nucleus) with electrons moving around the outside.
nucleus
the small, dense center of positive charge in an atom.
protons
a positively charged particle in an atomic nucleus.
neutrons
the small, dense center of positive charge in an atom.
atomic number
the number of protons in the nucleus of an atom.
mass number
the total number of protons and neutrons in the atomic nucleus of an atom.
chemical bonds
the force or, more accurately, the energy, that holds two atoms together in a compound.
molecule
a bonded collection of two or more atoms of the same or different elements.
chemical formula
the representation of a molecule in which the symbols for the elements are used to indicate the types of atoms present and subscripts are used to show the relative numbers of atoms.
structural formula
the representation of a molecule in which the relative positions of the atoms are shown and the bonds are indicated by lines.
space-filling model
a model of a molecule showing the relative sizes of the atoms and their relative orientations.
ball-and-stick models
a molecular model that distorts the sizes of atoms but shows bond relationships clearly.
anion
a negative ion.
ionic bonding
the electrostatic attraction between oppositely charged ions.
ionic solid
a solid containing cations and anions that dissolves in water to give a solution containing the separated ions which are mobile and thus free to conduct electrical current.
polyatomic ion
an ion containing a number of atoms.
periodic table
a chart showing all the elements arraigned in columns with similar chemical properties.
metals
an element that gives up electrons relatively easily and is lustrous, malleable, and a good conductor of heat and electricity.
nonmetals
an element not exhibiting metallic characteristics. Chemically, a typical nonmetal accepts electrons from a metal.
groups
a vertical column of elements having the same valence electron configuration and showing similar properties.
families
another word for groups, columns of elements on the periodic table
alkali metals
a group 1A metal.
alkaline earth metals
a group 2A metal.
halogens
a group 7A element.
noble gases
a group 8A element.
periods
horizontal rows in the periodic table
binary compunds
a two-element compound.
binary ionic compounds
compounds composed of two different elements
oxyanions
polyatomic ions that contain oxygen
acids
a substance that produces hydrogen ions in solution; a proton donor.