Identify VocabularyHighlight each vocabulary termyou read in this section. Also,highlight the definition of eachterm. After you read the section,go back and read the vocabularyterms and their definitionsagain.

●A Compare and ContrastMake the following Foldable tocompare and contrast howMendeleev and Moseley arrangedthe periodic table.

The Periodic Table

section ● Introduction to the Periodic Table1

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

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Before You ReadWrite what you think an element is on the lines below.

Development of the Periodic TablePeople who lived long ago knew about a few of the

substances that are now called elements. They used gold andsilver to make coins and jewelry. They used copper, tin, andiron to make tools. By 1830, scientists had found and named55 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 increasingatomic mass. Elements with similar properties made groups.Not all of the elements were known. So, Mendeleev left threespaces for missing elements. He predicted what the missingelements were like. Within 15 years, all three elements werefound. 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 elementsaccording to atomic number instead of atomic mass.Moseley put the elements in order of increasing number ofprotons in the nucleus. With Moseley’s table, it was easy tosee how many elements still had not been discovered.

chapter

315

Reading Essentials 221

Mendeleev Moseley

1. Identify What are theelements in Groups 3–12called?

Picture This2. Label Number the

groups of representativeand transition elementsfrom left to right. Start inthe top row of therepresentative elements onthe far left.

Today’s Periodic TableToday, the elements are still organized by increasing

atomic number. Look at the periodic table at the back ofyour textbook. The periods, or rows, are labeled 1–7. Aperiod is a row of elements whose properties changegradually. The periodic table has 18 columns. Each columnhas a group, or family, of elements. A group has elementsthat 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 inGroups 1 and 2 and the elements in Groups 13–18. Theyinclude metals, metalloids, and nonmetals. The transitionelements are the elements in Groups 3–12. They are allmetals. Some transition elements are placed below the maintable. These inner transition elements are called the lanthanideand actinide series. One series follows the element lanthanum,element 57. The other series follows actinium, element 89.

What are metals?The periodic table is divided into metals, nonmetals, and

metalloids. Examples of a metal, a nonmetal, and ametalloid are shown in the figure near the top of the nextpage. All of the metals except for mercury are solids. Mostmetals have high melting points. A metal is an element thathas luster, is a good conductor of heat and electricity, ismalleable (MAL yuh bul), and is ductile (DUK tul).

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222 The Periodic Table

Transition elements

Inner transition elements

Representativeelements

Representative elements

Lanthanide series

Actinide series

Picture This3. Identify Which of the

elements in the figureconducts heat well?

●B Draw and Label Use aquarter-sheet of paper to makean element key for hydrogen.Label each part of the elementkey.

Metal Properties Luster is the ability to reflect light. Agood conductor of heat and electricity lets heat andelectricity pass through it easily. Something that is malleablecan be shaped easily into objects or pounded into thinsheets. Something that is ductile can be stretched into wire.

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, oxy-gen, and phosphorus are nonmetals that are necessary for life.

The elements between metals and nonmetals on theperiodic table are metalloids (ME tuh loydz). A metalloid isan element that shares some properties with metals andsome with nonmetals. They are also called semimetals.

What does an element key show?Each element on the periodic

table has an element key. Thekey shows the name of theelement, its atomic number, itssymbol, and its average atomicmass. The figure shows theelement key for hydrogen.Element keys also have symbols that show an element’s stateof matter at room temperature. Gases are marked with aballoon. Solids are marked with a cube. Liquids are markedwith a drop. The elements that are not found naturally onEarth, or synthetic elements, are marked with a bull’s-eye.

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Reading Essentials 223

Hydrogen

1

H

1.008

Element

Atomic number

Symbol

Atomic mass

State of matter

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

Copper, a metal, is reflective, ductile, malleable, and agood conductor of heat andelectricity.

Carbon is a nonmetal. In graphite,carbon is a soft, brittle solid. It is notreflective, ductile, or malleable.

Hydrogen1H

1.008

4. Identify How manyletters do element symbolsin the periodic table have?

Picture This5. Explain Why is the

symbol for gold Au insteadof G?

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 thesymbol for vanadium and Sc is the symbol for scandium.Sometimes the symbols do not match the names. Ag is thesymbol for silver and Na is the symbol for sodium. In thosecases, the symbols might come from Greek or Latin namesfor the elements. Some elements are named for scientistssuch as Lise Meitner (meitnerium, Mt). Some are named forgeographic locations such as France (francium, Fr).

New Elements Newly discovered elements are given atemporary name and three-letter symbol. The symbol isrelated to the element’s atomic number. The InternationalUnion of Pure and Applied Chemistry (IUPAC) startedusing this system in 1978. When the discovery of an elementis confirmed, the discoverers can choose a name. The tableshows where some element names and symbols come from.

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224 The Periodic Table

Chemical Symbols and Their Origins

Name Sy olymbo the Name Comes FromWhere

Mendellevium Md mitri MendeleevFor Dim

Lead Pb in name for leadThe Latis bumplumb .

Thoriumm Th rse god of thunder is Thor.The Nor

Poloniuum Po and, where Marie Curie,For Polaus scientist, was borna famou

Hydroggen H reek words meaningFrom Gr“ former.water f ”

Mercuryy Hg gyrumHydrarg means“ silverliquid s ” in Greek.

Gold Au Aurum means m “shining dawn”.in Latin

Unununnium Uuu using the IUPACNamed g system.naming

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1. Read the key terms and definitions in the Mini Glossary above. Write a sentence that tellshow 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 thename of the group that has properties of both.

3. How would you explain to an elementary school student what the periodic table is?

After You ReadMini Glossarygroup: a collection of elements that have similar physical or

chemical propertiesmetal: an element that has luster, is a good conductor of

heat and electricity, is malleable, and is ductilemetalloid: an element that shares some properties with

metals and some with nonmetals

nonmetals: elements that are gases or brittle solids at roomtemperature and do not conduct heat and electricity well

period: a row of elements whose properties change graduallyrepresentative elements: the elements in Groups 1 and

2 and the elements in Groups 13–18transition elements: the elements in Groups 3–12

End ofSection

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Reading Essentials 225

Metals Nonmetals