Periodic Table Of The Elements

Hydrogen

Lithium B Li

6.941

Sodium 11 Na

22.990

Element — Hydrogen

Beryllium

9.012

Magnesium

M2gO

24.B05

Atomic number -Symbol -Atomic mass -

9 Gas

^ Liquid

Q Solid

Q Synthetic

/

Metal

/

Metalloid

/

Nonmetal

/

Recently

V

10.811

Aluminum 1B Al

26.982

Carbon 6

12.011

28.086

Nitrogen

14.007

Phosphorus ya

B0.974

Oxygen

15.999

B2.066

Fluorine

B5.45B

Helium

20.180

B9.948

Potassium

Calcium 20 Ca

40.078

Scandium 21 Sc 44.956

Titanium

47.867

Vanadium

50.942

Chromium

51.996

Manganese

M5,a

54.9B8

55.847

Cobalt

58.933

Nickel 28 Ni

58.69B

Copper

6B.546

65.B9

Gallium

69.723

Germanium B2 Ge

72.61

Arsenic

BB r

As L

74.922

Selenium

78.96

Bromine

B5 4

79.904

Krypton

36 0

Rubidium

85.468

Strontium

Sr a

87.62

Yttrium B9 Y

Zirconium

91.224

Nb LJI

92.906

Molybdenum mM.0

95.94

Technetium

Ruthenium

101.07

Rhodium

Rh a Rh

102.906

Palladium 46 Pd

106.42

107.868

Cadmium 48 Cd 112.411

Indium 49

114.82

Tin 50 Sn

118.710

Antimony s5ba

121.757

Tellurium 52 Te

127.60

Iodine 53

ii4 9

1B1.290

Cesium

C5sa

1B2.905

Barium

137.327

Lanthanum iaa

1B8.905

Hafnium

178.49

Tantalum

180.948

18B.84

Rhenium

186.207

Osmium

76 a

190.2B

Iridium

77 a

192.217

Platinum ta

Gold fa

196.967

Mercury 80 &

200.59

Thallium

204.383

Lead

207.2

Bismuth

208.980

Polonium

208.982

Astatine

209.987

Radon

86 9

Rn v

222.018

Francium 87 Fr

Radium

Actinium

Rutherfordium 104 ©

Dubnium 105 ©

Seaborgium s;6®

Bohrium 107 ©

Hassium 108 ©

Meitnerium 109 ©

Darmstadtium

Roentgenium

Ununbium

Ununtrium W 11B Uut

Ununquadium W 114 Uuq

Ununpentium W 115 Uup

Ununhexium W 116 Uuh

The number in parentheses is the mass number of the longest lived isotope for that element.

*The names and symbols for elements 112, 113, 114, 115, 116, and 118 are temporary. Final names will be selected when the elements' discoveries are verified.

Lanthanidi series

Actinidi series

Cerium

Tb a

D6 a

Ho a

T6m a

L7:a

P1 a

9U20

Bk w

;°rB® (262)

Sulfur

Chlorine

Ununoctium

Surrounding the nucleus of an atom are smaller particles called electrons. An electron (e) has little mass, but it has a negative electric charge that is exactly the same magnitude as the positive charge of a proton. An atom has an equal number of protons and electrons; thus, the electric charge of an electron cancels the positive charge of a proton to produce an atom that has no overall charge. Notice that the electrons in Figure 3.1 are shown as a cloudlike region surrounding the nucleus. This is because electrons are in constant motion around an atom's nucleus, and their exact positions at any given moment cannot be determined.

Symbols for elements There are 92 elements that occur naturally on Earth and in the stars. Other elements have been produced in laboratory experiments. Generally, each element is identified by a one-, two-, or three-letter abbreviation known as a chemical symbol. For example, the symbol H represents the element hydrogen, C represents carbon, and O represents oxygen. Elements identified in ancient times, such as gold and mercury, have symbols of Latin origin. For example, gold is identified by the symbol Au for its Latin name, aurum. All elements are classified and arranged according to their chemical properties in the periodic table of the elements, shown in Figure 3.2.

Figure 3.2 The periodic table of the elements is arranged so that a great deal of information about all of the known elements is provided in a small space.

□^rtCBptiiflMOU^

Interactive Figure To see an animation of the periodic table of elements, visit glencoe.com.

Mass number The number of protons and neutrons in atoms of different elements varies widely. The lightest of all atoms is hydrogen, which has only one proton in its nucleus. The heaviest naturally occurring atom is uranium. Uranium-238 has 92 protons and 146 neutrons in its nucleus. The number of protons in an atom's nucleus is its atomic number. The sum of the protons and neutrons is its mass number. Because electrons have little mass, they are not included in determining mass number. For example, the atomic number of uranium is 92, and its mass number is 238 (92 protons + 146 neutrons). Figure 3.3 explains how atomic numbers and mass numbers are listed in the periodic table of the elements.

Isotopes

Recall that all atoms of an element have the same number of protons. However, the number of neutrons of an element's atoms can vary. For example, all chlorine atoms have 17 protons in their nuclei, but they can have either 18 or 20 neutrons. This means that there are chlorine atoms with mass numbers of 35 (17 protons + 18 neutrons) and 37 (17 protons + 20 neutrons). Atoms of the same element that have different mass numbers are called isotopes. The element chlorine has two isotopes: Cl-35 and Cl-37. Because the number of electrons in an atom equals the number of protons, isotopes of an element have the same chemical properties.

Look again at the periodic table in Figure 3.2. Scientists have measured the mass of atoms of elements. The atomic mass of an element is the average of the mass numbers of the isotopes of an element. Most elements are mixtures of isotopes. For example, notice in Figure 3.2 that the atomic mass of chlorine is 35.453. This number is the average of the mass numbers of the naturally occurring isotopes of chlorine-35 and chlorine-37.

Identify Elements

What elements are in your classroom? Most substances on Earth occur in the form of chemical compounds. Around your classroom, there are numerous objects or substances that consist mostly of a single element.

Procedure

1. Read and complete the lab safety form.

2. Create a data table with the following column headings: Article, Element, Atomic Number, Properties.

3. Name three objects in your classroom and the three different elements of which they are made.

4. List the atomic numbers of these elements and describe some of their properties. Analysis

1. Categorize List two examples of a solid, a liquid, and a gaseous object or substance.

2. Compare and contrast liquids, solids, and gases.

Figure 3.3 The element chlorine is atomic number 17.

Infer In what state is chlorine at room temperature?

Figure 3.3 The element chlorine is atomic number 17.

Infer In what state is chlorine at room temperature?

Element Krypton Subatomic Particles

Radioactive isotopes The nuclei of some isotopes are unstable and tend to break down. When this happens, the isotope also emits energy in the form of radiation. Radioactive decay is the spontaneous process through which unstable nuclei emit radiation. In the process of radioactive decay, a nucleus can lose protons and neutrons, change a proton to a neutron, or change a neutron to a proton. Because the number of protons in a nucleus identifies an element, decay changes the identity of an element. For example, the isotope polonium-218 decays at a steady rate over time into bismuth-214. The polonium originally present in a rock is gradually replaced by bismuth. You will learn about the use of radioactive decay to calculate the ages of rocks in Chapter 21.

Electrons in Energy Levels

Although the exact position of an electron cannot be determined, scientists have discovered that electrons occupy areas called energy levels. Look again at Figure 3.1. The volume of an atom is mostly empty space. However, the size of an atom depends on the number and arrangement of its electrons.

Filling energy levels Figure 3.4 presents a model to help you visualize the position of atomic particles. Note that electrons are distributed over one or more energy levels in a predictable pattern. Keep in mind that the electrons are not sitting still in one place. Each energy level can hold only a limited number of electrons. For example, the smallest, innermost energy level can hold only two electrons, as illustrated by the oxygen atom in Figure 3.4. The second energy level is larger, and it can hold up to eight electrons. The third energy level can hold up to 18 electrons and the fourth energy level can hold up to 32 electrons. Depending on the element, an atom might have electrons in as many as seven energy levels surrounding its nucleus.

Figure 3.4 Electrons occupy one energy level in hydrogen, two energy levels in oxygen, and three energy levels in aluminum.

Nucleus

Hydrogen atom

Oxygen atom

Aluminum atom e e e e e e e e e e e e e e e e e e e

Figure 3.5 The inert nature of argon makes it an ideal gas to use inside an incandescent light bulb because it does not react with the extremely hot filament.

Figure 3.5 The inert nature of argon makes it an ideal gas to use inside an incandescent light bulb because it does not react with the extremely hot filament.

Animated Element Hafnium

Vocabulary

Academic vocabulary

Region a continuous part of an area or body, with or without definite boundaries or with certain characteristics The region surrounding the flood was labeled as a disaster area

Valence electrons The electrons in the outermost energy level determine the chemical behavior of the different elements. These outermost electrons are called valence electrons. Elements with the same number of valence electrons have similar chemical properties. For example, both a sodium atom, with the atomic number 11, and a potassium atom, with the atomic number 19, have one valence electron. Thus both sodium and potassium exhibit similar chemical behavior. These elements are highly reactive metals, which means that they combine easily with many other elements.

Elements such as helium and argon have full outermost energy levels. For example, an argon atom, shown in Figure 3.5, has 18 electrons, with two electrons in the first energy level and eight electrons in the second and outermost energy levels. Elements that have full outermost energy levels are highly unreactive. The gases helium, neon, argon, krypton, xenon, and radon have full outer energy levels.

Ions

Sometimes atoms gain or lose electrons from their outermost energy levels. Recall that atoms are electrically neutral because the number of electrons, which have negative charges, balances the number of protons, which have positive charges. An atom that gains or loses an electron has a net electric charge and is called an ion. In general, an atom in which the outermost energy level is less than half-full—that is, it has fewer than four valence electrons—tends to lose its valence electrons. When an atom loses valence electrons, it becomes positively charged. In chemistry, a positive ion is indicated by a superscript plus sign. For example, a sodium ion is represented by Na+. If more than one electron is lost, that number is placed before the plus sign. For example, a magnesium ion, which forms when a magnesium atom has lost two electrons, is represented by Mg2+.

^ Reading Check Explain what makes an ion positive.

An atom in which the outermost energy level is more than half-full—that is, it has more than four valence electrons—tends to fill its outermost energy level. Such an atom forms a negatively charged ion. Negative ions are indicated by a superscript minus sign. For example, a nitrogen atom that has gained three electrons is represented by N3. Some substances contain ions that are made up of groups of atoms—for example, silicate ions. These complex ions are important constituents of most rocks and minerals.

Abundance of Elements

In the Universe

In Earth's Crust

Hydrogen 93.5% Helium 6.3%

Oxygen 0.065% Carbon 0.039% Neon 0.009% Nitrogen 0.008% Magnesium 0.004% Silicon 0.004% Iron 0.003% Sulfur 0.002%

Hydrogen 93.5% Helium 6.3%

Oxygen 0.065% Carbon 0.039% Neon 0.009% Nitrogen 0.008% Magnesium 0.004% Silicon 0.004% Iron 0.003% Sulfur 0.002%

Oxygen 46.6%

What elements are most abundant?

Astronomers have identified the two most abundant elements in the universe as hydrogen and helium. All other elements account for less than 1 percent of all atoms in the universe, as shown in Figure 3.6. Analyses of the composition of rocks and minerals on Earth indicate that the percentages of elements in Earth's crust differ from the percentages in the universe. As shown in Figure 3.6, 98.5 percent of Earths crust is made up of only eight elements. Two of these elements, oxygen and silicon, account for almost 75 percent of the crust's composition. This means that most of the rocks and minerals on Earth's crust contain oxygen and silicon. You will learn more about these elements and the minerals they form in Chapter 4.

Iron 5.0% Calcium 3.6% Sodium 2.8% Potassium 2.6% Magnesium 2.1% All others 1.5%

Figure 3.6 The most abundant elements in the universe are greatly different from the most abundant elements on Earth. Hypothesize Where might most of the hydrogen and helium in the universe be found?

Oxygen 46.6%

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Responses

  • Salvia
    How many valence electrons are in ununbium?
    8 years ago
  • Eduardo
    Is chlorine radioactive?
    8 years ago
  • gabriel
    How does fish react in a light bulb?
    7 years ago
  • Leonardo Kelly
    What is the isotope for chlorine?
    7 years ago

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