Is copper pipe a pure substance

1.1 Matter and Its Classification 5

Phosphorus Copper Bromine Nickel Lead

Gold Carbon Aluminum Sulfur Tin

FIGURE 1.4 Some elements. Which of these are metals? (Phosphorus, Bromine, Nickel, Lead, Aluminum, Sulfer & Tin): ©McGraw-Hill Education/Stephen Frisch; (Copper): ©Jim Birk; (Gold): ©Digital Vision/Getty Images; (Carbon): ©Photodisc/Getty Images.

Carbon Magnesium

Sulfur Aluminum

EXAMPLE 1.1 Metals and Nonmetals

Which of the elements pictured are metals? Why do you think so?

Solution: Notice that three of the elements—iron, aluminum, and magnesium—have a luster; that is, they shine. They are metals. If you could handle and test the substances, you could use other properties, such as electrical conductivity, to distinguish between metals and nonmetals.

Consider This 1.1 What if you were given element properties and had to determine the identity of the element from a list of possibilities? Suppose an element is rather dull in ap- pearance, a poor conductor of electricity, and a gas at room temperature. Would this element be zinc, platinum, or chlorine?

Practice Problem 1.1 Identify the nonmetals in Figure 1.4. Explain the characteristics you considered in making your decision.

Further Practice: Questions 1.31 and 1.32 at the end of the chapter

IronIron

(Iron): ©Sinclair Stammers/Science Source; (Carbon): ©Photodisc/Getty Images; (Magnesium, Sulfur & Aluminum): ©McGraw-Hill Education/ Stephen Frisch.

6 Chapter 1 Matter and Energy

To avoid having to write out the name of an element every time we refer to it, we use a system of symbols. An element symbol is a shorthand version of an element’s longer name. Often, the symbol is one or two letters of the element’s name (C for carbon, He for helium, Li for lithium). The first letter is uppercase, and the second letter, if present, is lowercase. When the names of two elements start with the same two first letters (magnesium and manganese, for example), the symbol uses the first letter and a later letter to distinguish them (Mg for magnesium, Mn for manganese).

For a few elements, the symbols are based on their Latin names or on names from other languages. These are listed in Table 1.1. Some recently synthesized ele- ments have been named for famous scientists or locations. See the periodic table and list of elements on the first page of this book for a complete list of the modern names and symbols.

To become familiar with the periodic table, you should learn the names and symbols for the first 36 elements, as well as the symbols for silver, tin, gold, mercury, and lead. Your instructor may ask you to learn others.

TABLE 1.1 Symbols of Selected Elements

English Name

Original Name

Symbol

English Name

Original Name

Symbol

copper cuprum Cu potassium kalium K

gold aurum Au silver argentum Ag

iron ferrum Fe sodium natrium Na

lead plumbum Pb tin stannum Sn

mercury hydrargyrum Hg tungsten wolfram W

Compounds A compound, sometimes called a chemical compound, is a pure substance composed of two or more elements combined in definite proportions. A compound has properties different from those of its component elements. For example, iron pyrite can be broken down into its component elements, iron and sulfur, but its characteristics are different from both (Figure 1.5). Anna and Bill

Iron pyrite

IronSulfur

FIGURE 1.5 Iron pyrite is composed of the elements iron and sulfur. Iron is magnetic and can be separated from sulfur when the two exist as elements mixed together. Iron pyrite, a compound of iron and sulfur, is not magnetic. (left): ©McGraw-Hill Education/Doug Sherman; (right): ©McGraw-Hill Education/ Stephen Frisch

EXAMPLE 1.2 Element Symbols

Potassium is a soft, silver-colored metal that reacts vigorously with water. Write the symbol for the element potassium.

Solution: The symbol for potassium is K. In the periodic table, potassium is element 19 in group (column) IA (1) of the periodic table.

Consider This 1.2 What if you instinctively identified the element symbol as P or Po? Why are these symbols incorrect for potassium?

Practice Problem 1.2 (a) Lead is a soft, dull, silver-colored metal. Write the symbol for the element

lead. (b) The symbol for a common element used to make jewelry is Ag. What is the

name of this element?

Further Practice: Questions 1.39 and 1.40 at the end of the chapter

1.1 Matter and Its Classification 7

saw many compounds during their trek around campus. These, and all com- pounds, can be chemically separated into their component elements. Sand is a compound of silicon and oxygen. Water, as discussed earlier, is composed of hydrogen and oxygen. The cheese on their pizza contains many complex com- pounds, but each of the compounds contains carbon, hydrogen, oxygen, nitrogen, and a few other elements.

Chemists represent compounds with formulas based on the symbols for the elements that are combined in the compound. (Chemical formulas are not the same as the mathematical formulas that may be familiar to you, such as A = πr2 for the area of a circle.) A chemical formula describes the composition of a compound, using the symbols for the elements that make up the compound. Sub- script numbers show the relative proportions of the elements in the compound. If no subscript number is given for an element in a formula, then you may assume that the element has a relative proportion of one. For example, water is known to consist of one unit of oxygen and two units of hydrogen. This compound is rep- resented by the formula H2O. Sodium chloride, the chemical compound com- monly called table salt, contains equal portions of the elements sodium and chlorine. Its formula is therefore NaCl. We will discuss formulas in detail in Chapter 3.