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Representative Elements

Groups 1 and 2

Groups 1 and 2 are always found in nature combined with other elements. They’re called active metals because of their readiness to form new substances with other elements. They are all metals except hydrogen, the first element in Group 1. Although hydrogen is placed in Group 1, it shares properties with the elements in Group 1 and Group 17.

Alkali Metals The Group 1 elements have a specific family name—alkali metals. All the alkali metals are silvery solids with low densities and low melting points. These elements increase in their reactivity, or tendency to combine with other substances, as you move from top to bottom on the periodic table. Some uses of the alkali metals are shown in Figure 5.

Alkali metals are found in many items. Lithium batteries are used in cameras. Sodium chloride is common table salt. Sodium and potassium, dietary requirements, are found in small quan- tities in potatoes and bananas.

Figure 5 These items contain alkali metals.

Group 1 Alkali Metals

Lithium 3 Li

Sodium 11 Na

  • Recognize the properties of representative elements.

  • Identify uses for the representa- tive elements.

  • Classify elements into groups based on similar properties.

Many representative elements play key roles in your body, your envi- ronment, and in the things you use every day.

Review Vocabulary atomic number: the number of protons in the nucleus of a given element

New Vocabulary

  • alkali metal

  • alkaline earth metal

  • semiconductor

  • halogen

  • noble gas

Potassium 19 K

Rubidium 37 Rb

Cesium 55 Cs

Francium 87 Fr

SECTION 2 Representative Elements K

105

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