1. Sec. 7.1 & 9.1: Formation and Naming of Ions Valence Electrons The electrons responsible for the chemical properties of atoms, and are those in the outer energy level. Valence electrons - The s and p electrons in the outer energy level –the highest occupied energy level Core electrons -those in the energy levels below. Atoms in the same group (family)... –Have the same outer electron configuration. –Have the same valence electrons. The number of valence electrons are easily determined: the group number for a representative element Group 2A: Be, Mg, Ca, etc. 2 valence electrons – have 2 valence electrons

2. Sec. 7.1 & 9.1: Formation and Naming of Ions Electron Dot Diagrams A way of showing & keeping track of valence electrons. How to write them? Write the symbol - it represents the nucleus and inner (core) electrons Put one dot for each valence electron (8 maximum) They don’t pair up until they have to (Hund’s rule) X

3. The Electron Dot diagram for Nitrogen l Nitrogen has 5 valence electrons to show. l First we write the symbol. N l Then add 1 electron at a time to each side. Sec. 7.1 & 9.1: Formation and Naming of Ions

4. Learning Check A. X would be the electron dot formula for 1) Na2) K3) Al B. X would be the electron dot formula 1) B2) N3) P

5. Sec. 7.1 & 9.1: Formation and Naming of Ions Symbols of atoms with dots to represent the valence-shell electrons 1 2 13 14 15 16 17 18 H  He:            Li  Be   B   C   N   O  : F  : Ne :                    Na  Mg   Al   Si   P   S  : Cl  : Ar :        

6. Sec. 7.1 & 9.1: Formation and Naming of Ions The Octet Rule l Noble gases are unreactive in chemical reactions l In 1916, Gilbert Lewis used this fact to explain why atoms form certain kinds of ions and molecules l The Octet Rule: l The Octet Rule: in forming compounds, atoms tend to achieve a noble gas configuration; 8 in the outer level is stable l Each noble gas (except He) has 8 electrons in the outer level

7. Sec. 7.1 & 9.1: Formation and Naming of Ions Formation of Cations Metals lose electronsMetals lose electrons to attain a noble gas configuration. (cations)They make positive ions (cations) If we look at the electron configuration, it makes sense to lose electrons: Na 1s 2 2s 2 2p 6 3s 1 1 valence electron Na 1+ 1s 2 2s 2 2p 6 This is a noble gas configuration with 8 electrons in the outer level.

8. Sec. 7.1 & 9.1: Formation and Naming of Ions Electron Dots For Cations Metals will have few valence electrons (usually 3 or less); calcium has only 2 valence electrons Ca

9. Sec. 7.1 & 9.1: Formation and Naming of Ions Electron Dots For Cations Metals will have few valence electrons Metals will lose the valence electrons Ca

10. Sec. 7.1 & 9.1: Formation and Naming of Ions Electron Dots For Cations Metals will have few valence electrons Metals will lose the valence electrons Forming positive ions Ca 2+ NO DOTS NO DOTS are now shown for the cation. This is named the calcium ion.

11. Predicting Ionic Charges Group 1A: Lose 1 electron to form 1+ ions H 1+ Li 1+ Na 1+ K 1+ Rb 1+

12. Predicting Ionic Charges Group 2A: Loses 2 electrons to form 2+ ions Be 2+ Mg 2+ Ca 2+ Sr 2+ Ba 2+

13. Predicting Ionic Charges Group 3A: B 3+ Al 3+ Ga 3+ Loses 3 electrons to form 3+ ions

14. Predicting Ionic Charges Group 4A: Do they lose 4 electrons or gain 4 electrons? Do they lose 4 electrons or gain 4 electrons? Neither! Group 4A elements rarely form ions (they tend to share)

15. Let’s do Scandium, #21 1s 2 2s 2 2p 6 3s 2 3p 6 4s 2 3d 1The electron configuration is: 1s 2 2s 2 2p 6 3s 2 3p 6 4s 2 3d 1 Thus, it can lose 2e - (making it 2+), or lose 3e - (making 3+) Sc = Sc 2+ Scandium (II) ion Scandium (III) ion Sc = Sc 3+ Sec. 7.1 & 9.1: Formation and Naming of Ions

16. Predicting Ionic Charges Group B elements: Many transition elements Many transition elements have more than one possible oxidation state. have more than one possible oxidation state. Iron (II) = Fe 2+ Iron (III) = Fe 3+ Note the use of Roman numerals to show charges

17. Predicting Ionic Charges Some of the post-transition elements also Some of the post-transition elements also have more than one possible oxidation state. have more than one possible oxidation state. Tin (II) = Sn 2+ Lead (II) = Pb 2+ Tin (IV) = Sn 4+ Lead (IV) = Pb 4+

18. Predicting Ionic Charges Group B elements: Some transition elements Some transition elements have only one possible oxidation state, such as these three: have only one possible oxidation state, such as these three: Zinc = Zn 2+ Silver = Ag 1+ Cadmium = Cd 2+

19. Naming cations Two methods can clarify when more than one charge is possible: 1)Stock system – uses roman numerals in parenthesis to indicate the numerical value 2)Classical method – uses root word with suffixes (-ous, -ic) Does not give true value

20. Naming cations We will use the Stock system. Cation - if the charge is always the same (like in the Group A metals) just write the name of the metal. Transition metals can have more than one type of charge. –Indicate their charge as a roman numeral in parenthesis after the name of the metal (Table 9.2, p.255)

21. Exceptions: Some of the transition metals have only one ionic charge: –Do not need to use roman numerals for these: –Silver is always 1+ (Ag 1+ ) –Cadmium and Zinc are always 2+ (Cd 2+ and Zn 2+ )

22. Electron Dots For Cations Let’s do Silver, element #47 5s 2 4d 9Predicted configuration is: 1s 2 2s 2 2p 6 3s 2 3p 6 4s 2 3d 10 4p 6 5s 2 4d 9 5s 1 4d 10Actual configuration is: 1s 2 2s 2 2p 6 3s 2 3p 6 4s 2 3d 10 4p 6 5s 1 4d 10 Ag = Ag 1+ (can’t lose any more, charges of 3+ or greater are uncommon)

23. Electron Dots For Cations Silver did the best job it could, but it did not achieve a true Noble Gas configuration Instead, it is called a “pseudo-noble gas configuration”

24. Practice by naming these: Na 1+ Ca 2+ Al 3+ Fe 3+ Fe 2+ Pb 2+ Li 1+ sodium calcium aluminum iron (III) iron (II) lead (II) lithium

25. Write symbols for these: Potassium ion Magnesium ion Copper (II) ion Chromium (VI) ion Barium ion Mercury (II) ion K +1 Mg +2 Cu +2 Cr +4 Ba +2 Hg +2

26. Anions Electron Configurations: Anions Nonmetals gain electrons to attain noble gas configuration. They make negative ions (anions) S = 1s 2 2s 2 2p 6 3s 2 3p 4 = 6 valence electrons S 2- = 1s 2 2s 2 2p 6 3s 2 3p 6 = noble gas configuration. Halide ions are ions from chlorine or other halogens that gain electrons

27. Naming Anions Anions are always the same charge Change the monatomic element ending to – ide F 1- a Fluorine atom will become a Fluoride ion.

28. Predicting Ionic Charges Group 5A: Gains 3 Gains 3 electrons to form 3- ions N 3- P 3- As 3- Nitride Phosphide Arsenide

29. Predicting Ionic Charges Group 6A: Gains 2 Gains 2 electrons to form 2- ions O 2- S 2- Se 2- Oxide Sulfide Selenide

30. Predicting Ionic Charges Group 7A: Gains 1 electron to form Gains 1 electron to form 1- ions F 1- Cl 1- Br 1- Fluoride Chloride Bromide I 1- Iodide

31. Predicting Ionic Charges Group 8A: Stable noble gases do not form ions! Stable noble gases do not form ions!

32. Practice by naming these: Cl 1- N 3- Br 1- O 2- Ga 3+ chloride nitride bromide oxide gallium

33. Write symbols for these: Sulfide ion Iodide ion Phosphide ion Strontium ion S -2 I -1 P -3 Sr +2

34. Polyatomic ions are… Groups of atoms that stay together and have an overall charge, and one name. Usually end in –ate or -ite Acetate: C 2 H 3 O 2 1- Nitrate: NO 3 1- Nitrite: NO 2 1- Permanganate: MnO 4 1- Hydroxide: OH 1- and Cyanide: CN 1- ?

35. Sulfate: SO 4 2- Sulfite: SO 3 2- Carbonate: CO 3 2- Chromate: CrO 4 2- Dichromate: Cr 2 O 7 2- Phosphate: PO 4 3- Phosphite: PO 3 3- Ammonium: NH 4 1+ Know Table 9.3 on page 257 If the polyatomic ion begins with H, then combine the word hydrogen with the other polyatomic ion present: H 1+ + CO 3 2- → HCO 3 1- hydrogen + carbonate → hydrogen carbonate ion (One of the few positive polyatomic ions)