Atomic Weight

When new substances are found in nature or are produced in the laboratory, the first thing chemists try to determine is the chemical formula for the substance. This new compound, a substance made of two or more kinds of atoms, is analyzed to find what elements it is composed of. This is usually done by chemically separating the compound into its elements and then determining how much of each element was present. Chemical formulas tell how many atoms are in a compound, not the amount of mass. So the mass of each element must be expressed as a part of a mole by comparing it to the atomic weight. When expressed in this manner, the quantity is a way of representing how many atoms are present in the compound. These numbers of moles are expressed as ratios, reduced to the lowest whole numbers and then combined with the symbols for the elements to represent the simplest chemical formula.

Companies that produce raw materials or manufacture goods use atomic and molecular weights to help determine the amounts of reactants needed to produce a given amount of product. Or they can determine how much product they can produce from a given amount of reactant. Once again, the quantities involved in chemical reactions depend on how many atoms or molecules react, not on the amount of mass of each. So the known amount of reactant or product must be expressed as a part of a mole by comparing it to the molecular weight. Although other factors are involved in these determinations, this quantity, along with the balanced equation for the chemical reaction, allows chemists to figure out how much of any other reactant or product is involved in the reaction. Calculations of this type can save manufacturers many dollars because the amounts of chemicals needed to manufacture a product can be accurately determined. If a billion tires are produced in one year and one penny can be saved on each tire by not using more of a substance than can be reacted, it would be a substantial savings to the company of $10,000,000 per year.