a complete chemical unit. While a molecule is often thought of as consisting of more than one atom, this is not always true. For instance, helium has only one atom per molecule. The oxygen m

is the basic unit of measurement in chemistry. By definition, in modern chemistry, one mole represents the number of carbon atoms in exactly 12 grams of carbon 12 (C12).

is a unit that enables scientists to calculate the weight of any chemical substance, be it an element or a compound. Molar mass is the sum of all of the atomic masses in a formula. More info

the number of moles of a solute dissolved in a liter of solvent. Note: be careful not to confuse molality and molarity. Molality is represented by a small "m," whereas molarity is

is the number of moles of solute dissolved in one kilogram of solvent. Note: be careful not to confuse molality and molarity. Molality is represented by a small "m," whereas molari

Forms or species of an element that has the same numbers of protons (hence the same atomic number), but different numbers of neutrons, thus different atomic masses. Technically speaking if a

elements that do not exhibit the characteristics of metals. These elements differ markedly from metals in respect to electronegativity and thermal and electrical conductivity. These elements

elements belonging to Group 18 of the periodic table. These elements are very unreactive, however, they are not nonreactive as compounds containing these elements have been synthesized. Ther

a particle of matter that has a mass of 1.009 amu but no electrical charge. These particles are constituents of the nucleus of all elements except for hydrogen (H). Neutrons can exist in a f

One billionth of a meter (10-9 or 0.000000001 m) or ten Ångstroms.

an association of substances, which cannot be represented by a chemical formula. In a heterogeneous mixture the substances are not uniformly dispersed, as is the case in Italian salad dressi

this term is no longer commonly used by chemists, however, it refers to elements that exhibit some properties of metals and nonmetals. These elements tend to be semiconductors. is an extrem

Elements that form cations when compounds of it are in solution and oxides of the elements form hydroxides rather than acids in water. Most metals are conductors of electricity, have crystal

The temperature at which the crystals of a pure substance are in equilibrium with the liquid phase at atmospheric pressure. This temperature is commonly referred to as melting point when a s

An amorphous (non-crystalline) form of matter between a gas and a solid that has a definite volume, but no definite shape.

This structure is similar to high density polyethylene except that it is a less rigid and less dense form of the molecule.

The fourteen elements of the upper row on the inner-transition metals on the periodic table that follow the element lanthanum (#57). Some reference sources include lanthanum in this series o

the temperature scale used in chemistry, physics and some engineering calculations. Zero degrees Kelvin (-273 centigrade) is the temperature at which all thermal motion ceases. To convert fr

International Union of Pure and Applied Chemists, the standards body that among other things, makes recommendations regarding the names of newly discovered elements and forms other chemistry

The radius exhibited by an ion in an ionic crystal where the ions are packed together to a point where their outermost electronic orbitals are in contact with each other.