Formation of Ions. Ions formed when atoms gain or lose valence e - to achieve a stable octet

Transcription

1 Ionic Bonding

2 Formation of Ions Ions formed when atoms gain or lose valence e - to achieve a stable octet Cation Positively charged ion Forms when atom loses electrons Anion negatively charged ion Forms when atom gains electrons

3 Naming Ions Naming Metal as is (Sodium ion) non-metal with ide suffix (chloride)

4 Monatomic Ions + Transition Metals Monatomic ion = single atom with +/- charge Transition Metals always cations Use Roman numerals (stock system) to denote charge: For Fe+, cation name = iron(i) For Fe 2+, cation name = iron(ii) For Fe 3+, cation name = iron(iii) There are classical names for metals with ous and ic endings.

5 Polyatomic Ions Polyatomic ion = a charged species form from two or more atoms covalently bonded Cation: NH 4 + (ammonium) Anions: NO 3 - (nitrate), OH - (hydroxide) Acts as a unit NEVER change its structure! Most names end in ate or ite suffixes

6 Naming Ionic Compounds Ionic compound Made of metal + nonmetal Transfer electrons from metal to nonmetal Always electrically neutral Two parts - Cation and Anion Cation Always listed first Use name of element Anion Cation NaCl Monatomic Anion use ide suffix on element name Polyatomic Anion use name Anion

7 Naming Ionic Compounds For Transition Metals Use Roman numerals in name to denote charge of cation OR use classical name Example: FeCl 2 is iron (II) chloride or ferrous chloride FeCl 3 is iron (III) chloride or ferric chloride NaCl K 2 O Na 2 SO 4 Cu(NO 3 ) 2 Sodium chloride Potassium oxide Sodium sulfate Copper (II) nitrate

8 How Atoms make Compounds When elements react with each other: Atoms must collide with others and then bond together Collisions are between electron clouds not the nuclei of the atoms

9 Ionic Bonding Transfer of e - Sodium (Na = 1 e -, 1s 2 2s 2 2p 6 3s 1 ) collides with chlorine (Cl = 7 e -, 1s 2 2s 2 2p 6 3s 2 3p 5 ) to form sodium chloride (salt). BAM - Na s 1 e - transferred to Cl Na has 11 p +, and 10 e - Na + ion Cl has 17 p +, and 18 e - Cl - ion Cl 8 e - [Ar] Na 8 e- [Ne] Na + strongly electrically attracted to Cl -, forms ionic compound NaCl (salt) + -

10 Formulas Formula = unique designation of how a compound (ionic or covalent) is made up of elements Subscripts - how many of each type of atom No subscript shown - only one atom of element Example: NaCl - one Na atom and one Cl atom Example: AlBr 3 - one Al atom and three Br atoms

11 Formula unit - simplest ratio of atoms in formula Example: CaCl 2, Ca 2 Cl 4, and Ca 3 Cl 6 are all calcium chloride. CaCl 2 = simplest ratio = best formula for calcium chloride.

12 Ways To Write An Ionic Formula Charge Balance

13 Ionic Bonding Charge Balance Method Ca P - Calcium has two positives Phosphorus has three negatives

14 Ionic Bonding Charge Balance Method Ca P - Ca + + BUT Ca is not balanced now! Need to bring in another Ca to balance out P

15 Ionic Bonding Charge Balance Method Ca P - Ca + + P BUT P is not balanced now! - - Need to bring in another P to balance out Ca

16 Ionic Bonding Charge Balance Method Ca P - Ca + + P - - Need to bring in another Ca to balance out P Ca + + NOW It is all balanced!

17 Ionic Bonding Ca 3 P 2 Formula Unit

18 Ways To Write An Ionic Formula Crisscross Method

19 Ionic Bonding Crisscross Method Ca +2 P -3 (3) = 6 (2) = 6 Need the least common denominator

20 Ionic Bonding Crisscross Method Ca +2 P Just crisscross charges they become subscripts

21 Ionic Bonding Crisscross Method Ca P 3 2 Tells you how many of each you need

22 Ionic Bonding Ca 3 P 2 Formula Unit

23 Balancing Ionic Charge Criss-Cross method - simple way of writing names of neutral ionic compounds Al 3+ O 2- Al 3+ O 2- Al 2 O 3 Cation charge # Anion subscript Anion charge # Cation subscript Polyatomic Ions = use parenthesis Aluminum Sulfate = Al 2 (SO 4 ) 3

24 Criss-Cross Polyatomic Ions NEVER EVER CHANGE A SUBSCRIPT OF A POLYATOMIC ION! USE PARENTHESES TO SHOW THE NUMBER OF POLYATOMIC IONS! Al 3+ SO 4 2- Al 2 (SO 4 ) 3

25 Electron Dot diagrams A way of keeping track of valence electrons. Write the symbol. Put one dot for each valence electron Don t pair up until they have to X

26 The Electron Dot diagram for Nitrogen Nitrogen has 5 valence electrons. First we write the symbol. Then add 1 electron at a time to each side. Then pair up. N

27 Lewis Dot Diagrams (Electron Dot Structure) Lewis Dot Diagrams show valence e s on elements that are not transition metals Only the outermost s- and p- orbital electrons

28 Lewis Dot Diagrams Draw the Lewis Dot Diagrams for the following elements: O 1s 2 2s 2 2p 4 Cl [Ne]3s 2 3p 5 Cl O P 1s 2 2s 2 2p 6 3s 2 3p 3 P Li 1s 2 2s 1 Li Ne 1s 2 2s 2 2p 6 Ne Ca [Ar]4s 2 Ca

29 Electron Dots For Ions

30 Ionic Bonding Anions and cations are held together by opposite charges. Ionic compounds are called salts. Simplest ratio is called the formula unit. The bond is formed through the transfer of electrons. Electrons are transferred to achieve noble gas configuration.

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32 Properties of Ionic Compounds Crystalline structure. A regular repeating arrangement of ions in the solid. Ions are strongly bonded. Structure is rigid. High melting points- because of strong forces between ions.

33 Properties of Ionic Compounds NaCl forms a very regular structure: Each Na + ion surrounded by 6 Cl - ions Each Cl - ion is surrounded by six Na + ions Ions packed as closely as possible Most ionic compounds are: Crystalline solids at room temperature Have high melting points Dissolve into ions in water Conduct electrical current when dissolved in water

34 Crystalline structure Called Crystal Lattice

35 Do they Conduct? Conducting electricity is allowing charges to move. In a solid, the ions are locked in place. Ionic solids are insulators. How can we get them to Melt them! conduct? Dissolve in water!

36 Ionic solids are brittle

37 Ionic solids are brittle Strong Repulsion breaks crystal apart

38 Metallic Bonds How atoms are held together in the solid. Metals hold onto their valence electrons very weakly. Think of them as positive ions floating in a sea of electrons. Malleability, ductility, conductibility

39 Sea of Electrons Electrons are free to move through the solid. Metals conduct electricity

40 Malleable Electrons allow atoms to slide by

41 Malleable/Ductile Hammered into shape (bend). Ductile - drawn into wires

42 Bonding in Metals Metallic objects (like copper wire) are made up of closely packed atoms Crystalline structure (like ionic compounds) Valence e - can be modeled as a sea of electrons, with nucleus + core electrons acting like cations Valence e - are free to move! Alloy = homogenous mixture of metals Mixture is superior to base metals properties

43 Practice Sodium Ion Na + Phosphide ion P 3- Chloride Ion Cl - Strontium ion Sr 2+

44 Pb 2+ Lead(II) ion Sn 4+ Tin(IV) ion Be 2+ Beryllium ion S 2- Sulfide ion Practice

45 Practice Carbonate CO 2-3 Cyanide CN - NH4 + ammonium OH - hydroxide

46 Beryllium chloride BeCl 2 LiF Mixed Practice Lithium fluoride Sr 3 (PO 4 ) 2 Strontium phospate Calcium acetate Ca(C 2 H 3 O 2 ) 2