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THINK ABOUT IT

There are two bottles on a shelf in a chemistry lab. Each contains a substance that resembles diamonds. Bottle 1 is labeled C(s), and Bottle 2 is labeled ZrO₂(s). Does either bottle contain diamonds? Do both bottles contain diamonds?

What do chemical names and symbols tell you about matter?

To answer this question, you will explore

EXPLORING THE TOPIC

The Language of Chemistry

Some chemical names are used in daily language, such as aluminum and iron, which cookware and machinery are made of, and ammonia, which is used for cleaning. Other chemical names, such as sodium chloride for salt and calcium carbonate for chalk, are used mainly by chemists.

Names and Symbols

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Elements are the building materials of all matter. In total, there are about 115 known elements. A few are shown here.

Here are some things you might notice. The chemical symbols for the elements consist of one or two letters. The first letter is always capitalized. If there is a second letter, it is lowercase. An element can be a solid, liquid, or gas. Some elements are metals, some are not. Sometimes, the symbol for an element is an abbreviation for its name. Other times, the symbol comes from another source, such as a word in another language. For example, the symbol for iron is Fe from the Latin word ferrum, and the symbol for gold is Au from the Latin word aurum.

Elements combine in specific ratios to form compounds. A compound is represented by a chemical formula. For example, sodium chloride, or table salt, is NaCl, which tells you that salt is made of the elements sodium, Na, and chlorine, Cl, in a 1:1 ratio. The chemical formula for carbon dioxide is CO₂. The subscript number “2” in the formula indicates that the elements carbon and oxygen are combined in a 1:2 ratio. (If the subscript is 1, you normally don’t write it.)

Compounds can differ greatly in appearance and behavior from the elements that they are composed of. For example, sodium is a shiny metal and chlorine is a gas. They are very different from sodium chloride, table salt.

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These minerals contain copper, Cu. Notice that not one of them is copper colored.

Physical Form

Elements and compounds can exist as solids, liquids, or gases. These forms are called the phases of matter, and are represented by using (s), (l), or (g) after the chemical formula. For example, water in the gas phase is written as H₂O(g), water in the liquid phase is written as H₂O(l), and water in the solid phase as ice is written as H₂O(s).

There is another symbol for physical form, the symbol (aq) for aqueous. A substance is aqueous when it dissolves and forms a clear mixture with water. Many familiar liquids are actually aqueous solutions, such as grape juice, vinegar, and ocean water.

Most substances are a mixture of compounds. For example, an orange is a mixture of water, H₂O, fructose, C₆H₁₂O₆, citric acid, C₆H₈O₇, limonene, C₁₀H₁₆, and many other compounds. Notice that in mixtures, the components are not combined in a specific ratio. Some oranges are sweeter or more sour or more juicy because they have more fructose, citric acid, or water than other oranges. But the ratios of the elements in compounds never change. Water is always water, H₂O.

LESSON SUMMARY

What do chemical names and symbols tell you about matter?

All matter is composed of elements. Each element has a unique symbol. Elements combine with one another to form compounds. A chemical formula specifies which elements are present in a compound. The letters in chemical formulas are symbols for the elements, and the subscript numbers indicate the amount of each element in that substance. A chemical formula may also include the lowercase letters (s), (g), (l), and (aq), which stand for solid, gas, liquid, and aqueous.

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