The Periodic Table. Introduction to the Periodic Table. Before You Read. Read to Learn

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1 chapter 15 3 The Periodic Table section 1 Introduction to the Periodic Table Before You Read Write what you think an element is on the lines below. What You ll Learn the history of the periodic table how to read an element key how the periodic table is organized Read to Learn Development of the Periodic Table People who lived long ago knew about a few of the substances that are now called elements. They used gold and silver to make coins and jewelry. They used copper, tin, and iron to make tools. By 1830, scientists had found and named 55 different elements. The list of elements is still growing. What was Mendeleev s table of elements? Dmitri Mendeleev (men duh LAY uhf) was a Russian chemist. In 1869, he published his first periodic table. Mendeleev arranged the elements according to increasing atomic mass. Elements with similar properties made groups. Not all of the elements were known. So, Mendeleev left three spaces for missing elements. He predicted what the missing elements were like. Within 15 years, all three elements were found. They were gallium, scandium, and germanium. How did Moseley add to the periodic table? In the early 1900s, the English physicist Henry Moseley rearranged Mendeleev s table. He arranged the elements according to atomic number instead of atomic mass. Moseley put the elements in order of increasing number of protons in the nucleus. With Moseley s table, it was easy to see how many elements still had not been discovered. Identify Vocabulary Highlight each vocabulary term you read in this section. Also, highlight the definition of each term. After you read the section, go back and read the vocabulary terms and their definitions again. A Compare and Contrast Make the following Foldable to compare and contrast how Mendeleev and Moseley arranged the periodic table. Mendeleev Moseley Reading Essentials 221

a few of the substances that are now called elements. They used gold and silver to make coins and jewelry. They used copper, tin, and iron to make tools.

2 1. Identify What are the elements in Groups 3 12 called? Today s Periodic Table Today, the elements are still organized by increasing atomic number. Look at the periodic table at the back of your textbook. The periods, or rows, are labeled 1 7. A period is a row of elements whose properties change gradually. The periodic table has 18 columns. Each column has a group, or family, of elements. A group has elements that have similar physical or chemical properties. How is the periodic table divided? The periodic table can be divided into parts. Look at the figure below. The representative elements are the elements in Groups 1 and 2 and the elements in Groups They include metals, metalloids, and nonmetals. The transition elements are the elements in Groups They are all metals. Some transition elements are placed below the main table. These inner transition elements are called the lanthanide and actinide series. One series follows the element lanthanum, element 57. The other series follows actinium, element 89. Representative elements Representative elements 2. Label Number the groups of representative and transition elements from left to right. Start in the top row of the representative elements on the far left. Lanthanide series Actinide series Transition elements Inner transition elements What are metals? The periodic table is divided into metals, nonmetals, and metalloids. Examples of a metal, a nonmetal, and a metalloid are shown in the figure near the top of the next page. All of the metals except for mercury are solids. Most metals have high melting points. A metal is an element that has luster, is a good conductor of heat and electricity, is malleable (MAL yuh bul), and is ductile (DUK tul). 222 The Periodic Table

Each column has a group, or family, of elements. A group has elements that have similar physical or chemical properties. How is the periodic table divided?

3 Metal Properties Luster is the ability to reflect light. A good conductor of heat and electricity lets heat and electricity pass through it easily. Something that is malleable can be shaped easily into objects or pounded into thin sheets. Something that is ductile can be stretched into wire. Boron, a metalloid, has a slight luster and conducts electricity at high temperatures like a metal. But like a nonmetal, boron is brittle and does not conduct electricity well at low temperatures. Carbon is a nonmetal. In graphite, carbon is a soft, brittle solid. It is not reflective, ductile, or malleable. Copper, a metal, is reflective, ductile, malleable, and a good conductor of heat and electricity. What are nonmetals and metalloids? Nonmetals are usually gases or brittle solids at room temperature. They do not conduct heat and electricity well. Brittle solids break apart easily. Carbon, sulfur, nitrogen, oxygen, and phosphorus are nonmetals that are necessary for life. The elements between metals and nonmetals on the periodic table are metalloids (ME tuh loydz). A metalloid is an element that shares some properties with metals and some with nonmetals. They are also called semimetals. What does an element key show? Each element on the periodic Element Hydrogen table has an element key. The Atomic number 1 key shows the name of the Symbol H element, its atomic number, its Atomic mass symbol, and its average atomic mass. The figure shows the element key for hydrogen. Element keys also have symbols that show an element s state of matter at room temperature. Gases are marked with a balloon. Solids are marked with a cube. Liquids are marked with a drop. The elements that are not found naturally on Earth, or synthetic elements, are marked with a bull s-eye. State of matter 3. Identify Which of the elements in the figure conducts heat well? B Draw and Label Use a quarter-sheet of paper to make an element key for hydrogen. Label each part of the element key. Hydrogen 1 H Reading Essentials 223

Boron, a metalloid, has a slight luster and conducts electricity at high temperatures like a metal. But like a nonmetal, boron is brittle and does not conduct electricity well at low temperatures.

4 4. Identify How many letters do element symbols in the periodic table have? What are element symbols? The symbols for the elements are either one or two letters, often based on the element s name. For example, V is the symbol for vanadium and Sc is the symbol for scandium. Sometimes the symbols do not match the names. Ag is the symbol for silver and Na is the symbol for sodium. In those cases, the symbols might come from Greek or Latin names for the elements. Some elements are named for scientists such as Lise Meitner (meitnerium, Mt). Some are named for geographic locations such as France (francium, Fr). New Elements Newly discovered elements are given a temporary name and three-letter symbol. The symbol is related to the element s atomic number. The International Union of Pure and Applied Chemistry (IUPAC) started using this system in When the discovery of an element is confirmed, the discoverers can choose a name. The table shows where some element names and symbols come from. Chemical Symbols and Their Origins Name Symbol Where the Name Comes From 5. Explain Why is the symbol for gold Au instead of G? Mendelevium Md For Dimitri Mendeleev Lead Pb The Latin name for lead is plumb bum. Thorium Th The Norse god of thunder is Thor. Polonium Po For Poland, where Marie Curie, a famous scientist, was born Hydrogen H From Greek words meaning water former. Mercury Hg Hydrarg gyrum means liquid silver in Greek. Gold Au Aurum means shining dawn in Latin. Unununium Uuu Named using the IUPAC naming system. 224 The Periodic Table

In those cases, the symbols might come from Greek or Latin names for the elements. Some elements are named for scientists such as Lise Meitner (meitnerium, Mt).

5 After You Read Mini Glossary group: a collection of elements that have similar physical or chemical properties metal: an element that has luster, is a good conductor of heat and electricity, is malleable, and is ductile metalloid: an element that shares some properties with metals and some with nonmetals nonmetals: elements that are gases or brittle solids at room temperature and do not conduct heat and electricity well period: a row of elements whose properties change gradually representative elements: the elements in Groups 1 and 2 and the elements in Groups transition elements: the elements in Groups Read the key terms and definitions in the Mini Glossary above. Write a sentence that tells how to locate a period and a group on the periodic table of elements. 2. In the Venn diagram, write properties of metals and nonmetals. In the middle, write the name of the group that has properties of both. Metals Nonmetals 3. How would you explain to an elementary school student what the periodic table is? Visit blue.msscience.com to access your textbook, interactive games, and projects to help you learn more about the periodic table. End of Section Reading Essentials 225

conduct heat and electricity well period: a row of elements whose properties change gradually representative elements: the elements in Groups 1 and 2 and the elements in Groups 13 18 transition

PERIODIC TABLE. reflect

PERIODIC TABLE. reflect reflect Suppose you wanted to organize your locker at school. How could you separate and arrange everything in an organized way? You could place the books, notebooks, and folders on a shelf that is separate