7.1 Ions > Chapter 7 Ionic and Metallic Bonding. 7.1 Ions. 7.2 Ionic Bonds and Ionic Compounds 7.3 Bonding in Metals

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1 Chapter 7 Ionic and Metallic Bonding 7.1 Ions 7.2 Ionic Bonds and Ionic Compounds 7.3 Bonding in Metals 1 Copyright Pearson Education, Inc., or its affiliates. All Rights Reserved.

2 CHEMISTRY & YOU What is fool s gold? Pyrite (FeS 2 ) is often mistaken for gold hence its nickname, fool s gold. Pyrite is an example of a crystalline solid. 2 Copyright Pearson Education, Inc., or its affiliates. All Rights Reserved.

3 Valence Electrons Valence Electrons How do you find the number of valence electrons in an atom of a representative element? 3 Copyright Pearson Education, Inc., or its affiliates. All Rights Reserved.

4 Valence Electrons Valence electrons are the electrons in the highest occupied energy level of an element s atoms. 4 Copyright Pearson Education, Inc., or its affiliates. All Rights Reserved.

5 Valence Electrons Valence electrons are the electrons in the highest occupied energy level of an element s atoms. The number of valence electrons largely determines the chemical properties of an element. 5 Copyright Pearson Education, Inc., or its affiliates. All Rights Reserved.

6 Valence Electrons Determining the Number of Valence Electrons To find the number of valence electrons in an atom of a representative element, simply look at its group (A) number. 6 Copyright Pearson Education, Inc., or its affiliates. All Rights Reserved.

7 Valence Electrons Atoms of the Group 1A elements (hydrogen, lithium, sodium, and so forth) all have one valence electron, corresponding to the 1 in 1A. Carbon and silicon atoms, in Group 4A, have four valence electrons. The noble gases (Group 8A) are the only exceptions to the group-number rule. Exception: Atoms of helium (in Group 8A) have two valence electrons 7 Copyright Pearson Education, Inc., or its affiliates. All Rights Reserved.

8 Valence Electrons Valence electrons are usually the only electrons involved in chemical bonds. As a general rule, only the valence electrons are shown in electron dot structures. Electron dot structures are diagrams that show valence electrons in the atoms of an element as dots. 8 Copyright Pearson Education, Inc., or its affiliates. All Rights Reserved.

9 Period Interpret Data Electron Dot Structures of Some Group A Elements Group 1A 2A 3A 4A 5A 6A 7A 8A This table shows electron dot structures for atoms of some Group A elements. Notice that all the electrons within a given group (with the exception of helium) have the same number of electron dots in their structures. 9 Copyright Pearson Education, Inc., or its affiliates. All Rights Reserved.

10 Generally you write the dots: left, right, top, bottom, then counterclockwise from the top. 10 Copyright Pearson Education, Inc., or its affiliates. All Rights Reserved.

11 Valence Electrons The Octet Rule Noble gases, such as neon and argon, are nonreactive in chemical reactions. That is, they are stable. 11 Copyright Pearson Education, Inc., or its affiliates. All Rights Reserved.

12 Valence Electrons In 1916, chemist Gilbert Lewis used this fact to explain why atoms form certain kinds of ions and molecules. He called his explanation the octet rule. 12 Copyright Pearson Education, Inc., or its affiliates. All Rights Reserved.

13 Valence Electrons The octet rule states that in forming compounds, atoms tend to achieve the electron configuration of a noble gas. An octet is a set of eight. Atoms of each of the noble gases (except helium) have eight electrons in their highest occupied energy levels and the general electron configuration of ns 2 np Copyright Pearson Education, Inc., or its affiliates. All Rights Reserved.

14 Valence Electrons Atoms of metals tend to lose their valence electrons, leaving a complete octet in the next-lowest energy level. Atoms of some nonmetals tend to gain electrons or share electrons with another nonmetal atom or atoms to achieve a complete octet. 14 Copyright Pearson Education, Inc., or its affiliates. All Rights Reserved.

15 Draw 7.1 Ions the > electron dot structure for bismuth. Bi Lithium Li Fluorine Neon F Ne 15

16 Formation of Cations Formation of Cations How are cations formed? 16 Copyright Pearson Education, Inc., or its affiliates. All Rights Reserved.

17 Formation of Cations Formation of Cations How are cations formed? An atom is electrically neutral because it has equal numbers of protons and electrons. An ion forms when an atom or group of atoms loses or gains electrons. 17 Copyright Pearson Education, Inc., or its affiliates. All Rights Reserved.

18 Formation of Cations A positively charged ion, or cation, is produced when an atom loses one or more valence electrons. CA+ION 18 Copyright Pearson Education, Inc., or its affiliates. All Rights Reserved.

19 Formation of Cations A positively charged ion, or cation, is produced when an atom loses one or more valence electrons. A sodium atom (Na) forms a sodium cation (Na + ). A calcium atom (Ca) forms a calcium cation (Ca + ). 19 Copyright Pearson Education, Inc., or its affiliates. All Rights Reserved.

20 Formation of Cations Group 1A Cations The most common cations are those produced by the loss of valence electrons from metal atoms. Most of these atoms have one to three valence electrons, which are easily removed. 20 Copyright Pearson Education, Inc., or its affiliates. All Rights Reserved.

21 Formation of Cations Group 1A Cations When forming a compound, a sodium atom loses its one valence electron and is left with an octet in what is now its highest occupied energy level. The number of protons in the sodium nucleus is still eleven, so the loss of one unit of negative charge produces a cation with a charge of 1+. Na 1s 2 2s 2 2p 6 3s 1 e Na + 1s 2 2s 2 2p 6 octet 21 Copyright Pearson Education, Inc., or its affiliates. All Rights Reserved.

22 Formation of Cations Group 1A Cations Both the sodium ion and the neon atom have eight electrons in their valence shells (highest occupied energy levels). 22 Copyright Pearson Education, Inc., or its affiliates. All Rights Reserved.

23 Formation of Cations Group 2A Cations Magnesium (atomic number 12) belongs to Group 2A of the periodic table, so magnesium atoms have two valence electrons. Mg Magnesium atom (electrically neutral, charge = 0) 23 Copyright Pearson Education, Inc., or its affiliates. All Rights Reserved.

24 Formation of Cations Group 2A Cations Magnesium (atomic number 12) belongs to Group 2A of the periodic table, so magnesium atoms have two valence electrons. A magnesium atom attains the electron configuration of a neon atom by losing both valence electrons and producing a magnesium cation with a charge of 2+. loses all its valence Mg Mg e Magnesium atom (electrically neutral, charge = 0) electrons Magnesium ion (2+ indicates two units of positive charge) (2 in front of e indicates two units of negative charge) 24 Copyright Pearson Education, Inc., or its affiliates. All Rights Reserved.

25 Formation of Cations The figure at right lists the symbols of the cations formed by metals in Groups 1A and 2A. Cations of Group 1A elements always have a charge of 1+. Cations of Group 2A elements always have a charge of Copyright Pearson Education, Inc., or its affiliates. All Rights Reserved.

26 Formation of Cations Transition Metal Cations The charges of cations of the transition metals may vary. An atom of iron may lose two valence electrons, forming the Fe 2+ cation, or three valence electrons, forming the Fe 3+ cation. 26 Copyright Pearson Education, Inc., or its affiliates. All Rights Reserved.

27 Formation of Cations Transition Metal Cations Some ions formed by transition metals do not have noble-gas electron configurations (ns 2 np 6 ) and are therefore exceptions to the octet rule. Silver, with the electron configuration of 1s 2 2s 2 2p 6 3s 2 2p 6 3d 10 4s 2 4p 6 4d 10 5s 1, is an example. To achieve the structure of krypton, a silver atom would have to lose eleven electrons. To acquire the electron configuration of xenon, a silver atom would have to gain seven electrons. Ions with charges of three or greater are uncommon. 27 Copyright Pearson Education, Inc., or its affiliates. All Rights Reserved.

28 Formation of Cations Transition Metal Cations A copper atom loses its lone 4s electron to form a copper ion (Cu + ) with a pseudo noble-gas electron configuration, as illustrated below. 28 Copyright Pearson Education, Inc., or its affiliates. All Rights Reserved.

29 CHEMISTRY & YOU Fool s gold is composed of iron(ii) cations (Fe 2+ ) and disulfide anions (S 2 2 ). Write the electron configuration of the Fe 2+ ion. 29 Copyright Pearson Education, Inc., or its affiliates. All Rights Reserved.

30 CHEMISTRY & YOU Fool s gold is composed of iron(ii) cations (Fe 2+ ) and disulfide anions (S 2 2 ). Write the electron configuration of the Fe 2+ ion. Fe: 1s 2 2s 2 2p 6 3s 2 3p 6 3d 6 4s 2 Fe 2+ : 1s 2 2s 2 2p 6 3s 2 3p 6 3d 6 30 Copyright Pearson Education, Inc., or its affiliates. All Rights Reserved.

31 How does a cesium atom form a cation? A. By losing 2 electrons B. By gaining 1 electron C. By losing 1 electron D. By gaining 2 electrons 31 Copyright Pearson Education, Inc., or its affiliates. All Rights Reserved.

32 How does a cesium atom form a cation? A. By losing 2 electrons B. By gaining 1 electron C. By losing 1 electron D. By gaining 2 electrons 32 Copyright Pearson Education, Inc., or its affiliates. All Rights Reserved.

33 Formation of Anions Formation of Anions How are anions formed? 33 Copyright Pearson Education, Inc., or its affiliates. All Rights Reserved.

34 Formation of Anions An anion is produced when an atom gains one or more valence electrons. ANION 34 Copyright Pearson Education, Inc., or its affiliates. All Rights Reserved.

35 Formation of Anions An anion is produced when an atom gains one or more valence electrons. Note that the name of an anion of a nonmetallic element is not the same as the element name. The name of the anion typically ends in -ide. Thus, a chlorine atom (Cl) forms a chloride anion (Cl ). An oxygen atom (O) forms an oxide anion (O 2 ). 35 Copyright Pearson Education, Inc., or its affiliates. All Rights Reserved.

36 Formation of Anions Atoms of nonmetals and metalloids form anions by gaining enough valence electrons to attain the electron configuration of the nearest noble gas. 36 Copyright Pearson Education, Inc., or its affiliates. All Rights Reserved.

37 Formation of Anions Atoms of nonmetallic elements attain noble-gas electron configurations more easily by gaining electrons than by losing them because these atoms have relatively full valence shells. 37 Copyright Pearson Education, Inc., or its affiliates. All Rights Reserved.

38 Formation of Anions Atoms of nonmetallic elements attain noble-gas electron configurations more easily by gaining electrons than by losing them because these atoms have relatively full valence shells. Atoms of chlorine have seven valence electrons. A gain of one electron gives a chlorine atom an octet and converts a chlorine atom into a chloride atom. +e Cl 1s 2 2s 2 2p 6 3s 2 3p 5 Cl 1s 2 2s 2 2p 6 3s 2 3p 6 octet 38 Copyright Pearson Education, Inc., or its affiliates. All Rights Reserved.

39 Formation of Anions Chlorine atoms need one more valence electron to achieve the electron configuration of the nearest noble gas. 39 Copyright Pearson Education, Inc., or its affiliates. All Rights Reserved.

40 Formation of Anions The ions produced when atoms of chlorine and other halogens gain electrons are called halide ions. All halogen atoms have seven valence electrons and need to gain only one electron to achieve the electron configuration of a noble gas. All halide ions (F, Cl, Br, and I ) have a charge of Copyright Pearson Education, Inc., or its affiliates. All Rights Reserved.

41 Formation of Anions Oxygen is in Group 6A, and an oxygen atom has six valence electrons. An oxygen atom attains the electron configuration of neon by gaining two electrons. 41 Copyright Pearson Education, Inc., or its affiliates. All Rights Reserved.

42 Interpret Data This table lists some common anions. Some Common Anions Name Symbol Charge Fluoride F 1 Chloride Cl 1 Bromide Br 1 Iodide I 1 Oxide O 2 2 Sulfide S 2 2 Nitride N 3 3 Phosphide P Copyright Pearson Education, Inc., or its affiliates. All Rights Reserved.

43 What is the electron configuration of a sulfide ion? What noble gas shares this configuration? 43 Copyright Pearson Education, Inc., or its affiliates. All Rights Reserved.

44 What is the electron configuration of a sulfide ion? What noble gas shares this configuration? S 2 : 1s 2 2s 2 2p 6 3s 2 3p 6 This is the same configuration as Ar. 44 Copyright Pearson Education, Inc., or its affiliates. All Rights Reserved.

45 Element Valence 7.1 Ions > Formation of Anions Lewis Dot Charge S 6ve S S -2 B 3ve B B +3 Na 1ve Na Na +1 Br 7ve Br Br -1 Sr 2ve Sr Sr +2 Al 3ve Al Al +3 Fr 1ve Fr Fr +1 N 5ve N N -3 45

46 Element Charge 7.1 Ions > 46 Formation of Anions Ion/Lewis Dot Noble Gas S S -2 S -2 Ar B B +3 B +3 He Na Na +1 Na +1 Ne Br Br -1 Br -1 Kr Sr Sr +2 Sr +2 Kr Al Al +3 Al +3 Ne Fr Fr +1 Fr +1 Rn N N -3 N Ne

47 Element 7.1 Ions > Electron Configuration Formation of Anions B 1s 2 2s 2 2p 1 B +3 1s 2 Na 1s 2 2s 2 2p 6 3s 1 Na +1 1s 2 2s 2 2p 6 Br 1s 2 2s 2 2p 6 3s 2 3p 6 3d 10 4s 2 4p 5 Br -1 1s 2 2s 2 2p 6 3s 2 3p 6 4s 2 3d 10 4p 6 Sr 1s 2 2s 2 2p 6 3s 2 3p 6 3d 10 4s 2 4p 6 5s 2 Sr +2 1s 2 2s 2 2p 6 3s 2 3p 6 3d 10 4s 2 4p 6 Al 1s 2 2s 2 2p 6 3s 2 3p 1 Al +3 1s 2 2s 2 2p 6 47

48 Key Concepts To find the number of valence electrons in an atom of a representative element, simply look at its group number. A positively charged ion, or cation, is produced when an atom loses one or more valence electrons. An anion is produced when an atom gains one or more valence electrons. 48 Copyright Pearson Education, Inc., or its affiliates. All Rights Reserved.

49 Glossary Terms valence electron: an electron in the highest occupied energy level of an atom electron dot structure: a notation that depicts valence electrons as dots around the atomic symbol of the element; the symbol represents the inner electrons and atomic nucleus; also called Lewis dot structure 49 Copyright Pearson Education, Inc., or its affiliates. All Rights Reserved.

50 Glossary Terms octet rule: atoms react by gaining or losing electrons so as to acquire the stable electron structure of a noble gas, usually eight valence electrons halide ion: a negative ion formed when a halogen atom gains an electron 50 Copyright Pearson Education, Inc., or its affiliates. All Rights Reserved.

51 BIG IDEA Bonding and Interactions Atoms form positive ions (cations) by losing valence electrons and form negative ions (anions) by gaining valence electrons. 51 Copyright Pearson Education, Inc., or its affiliates. All Rights Reserved.

52 END OF Copyright Pearson Education, Inc., or its affiliates. All Rights Reserved.