Octet Rule = atoms tend to gain, lose or share electrons so as to have 8 electrons C would like to N would like to O would like to Gain 4 electrons Gain 3 electrons Gain 2 electrons

Electron Dot Structures Symbols of atoms with dots to represent the valence-shell electrons H  He:            Li  Be   B   C   N   O  : F  : Ne :                    Na  Mg   Al   Si   P   S  : Cl  : Ar :        

Chemical bond A chemical bond forms when outer-shell electrons of different atoms come close enough to each other to interact and rearrange themselves into a more stable arrangement.

Types of Chemical Bonds Ionic bonds formed when metal atoms combined with non-metal atoms Metallic bonds formed when metal atoms combined with metal atoms. Covalent bonds formed when non-metal atoms combined with non-metal atoms.

Ionic Compounds

1). Ionic bond – electron from Na is transferred to Cl, this causes a charge imbalance in each atom. The Na becomes (Na+) and the Cl becomes (Cl-), charged particles or ions.

How many chlorine ions surround each sodium ion and vice versa? NaCl coordination number- 6:6 The coordination number of an ionic lattice is written as a ratio x:y

Hardness and Brittleness  Figure 6.4 The repulsion between like charges causes this sodium chloride crystal to shatter when it is hit sharply.

Electrical Conductivity In the solid form, ions in sodium chloride are held in the crystal lattice and are not free to move so cannot conduct electricity. When the solid melts the ions are free to move. In a similar way, when sodium chloride dissolves in water, the ions separate and are free to move towards the opposite charge.

Properties of Ionic Compounds –Forms crystal composed of 3d array of ions (ionic network lattice) –Have high melting and boiling temperatures. –Are hard but brittle –Do NOT conduct electricity in the solid state –They will only conduct electricity if they are melted or dissolved in water.

Structure From the properties we can conclude: –The forces between the particles are strong. –There are no free-moving electrons present, unlike in metals. –There are charged particles present, but in solid state they are not free to move. –When an ionic compound melts, however, the particles are free to move and the compound will conduct electricity.

Use Electron shell diagram and simple equation to show the formation of: NaCl MgO

Naming Binary Ionic Compounds Contain 2 different elements Name the metal first, then the nonmetal as -ide. Examples: NaClsodium chloride ZnI 2 zinc iodide Al 2 O 3 aluminum oxide

Practise Complete the names of the following binary compounds: Na 3 N________________ KBr________________ Al 2 O 3 ________________ MgS_________________________

Solution Complete the names of the following binary compounds: Na 3 Nsodium nitride KBrpotassium bromide Al 2 O 3 aluminum oxide MgSmagnesium sulfide

Transition Metals Many form 2 or more positive ions or or 3+ Ag + Cd 2+ Cu +, Cu 2+ Fe 2+, Fe 3+ silver cadmium copper(I) ion iron(II) ion ion ion copper (II) ion iron(III) ion Zn 2+ zinc ion

Write symbols for these: Potassium ion Magnesium ion Copper (II) ion Chromium (VI) ion Barium ion Mercury (II) ion

Formula of ionic compounds

Criss-Cross Method 1.Write the symbols for the ions side by side. Write the cation first. Al 3+ O 2-Al 3+ O 2- 1.Write the symbols for the ions side by side. Write the cation first. Al 3+ O 2-Al 3+ O 2- 2.Cross over the charges by using the absolute value of each ion’s charge as the subscript for the other ion. Al 2 O 3Al 2 O 3 3. Check the subscripts and divide them by their largest common factor to give the smallest possible whole-number ratio of ions. Then write the formula. Al 2 O 3 Al 2 O 3 For Al: 2 x 3 + = 6 + For O: 3 x 2 - = 6 -For Al: 2 x 3 + = 6 + For O: 3 x 2 - = Cross over the charges by using the absolute value of each ion’s charge as the subscript for the other ion. Al 2 O 3Al 2 O 3 3. Check the subscripts and divide them by their largest common factor to give the smallest possible whole-number ratio of ions. Then write the formula. Al 2 O 3 Al 2 O 3 For Al: 2 x 3 + = 6 + For O: 3 x 2 - = 6 -For Al: 2 x 3 + = 6 + For O: 3 x 2 - = 6 -

Example 1: Calcium and Oxygen Calcium Ca 2+ Oxide O 2- Ca 2 O 2 Criss-Cross Method CaO

Example 2: Magnesium and Phosphorus Magnesium Mg 2+ Phosphorus P 3- Mg 3 P 2 Criss-Cross Method The sum of the cation charge and the sum of the anion charge must cancel each other so that the compound formed is neutral.

Practise 1. The formula for the ionic compound of Na + and O 2- is 1) NaO2) Na 2 O3) NaO 2 2. The formula of a compound of aluminum and chlorine is 1) Al 3 Cl2) AlCl 2 3) AlCl 3 3. The formula of Fe 3+ and O 2- is 1) Fe 3 O 2 2) FeO 3 3) Fe 2 O 3

Solution A. The formula for the ionic compound of Na + and O 2- is 2) Na 2 O B. The formula of a compound of aluminum and chlorine is 3) AlCl 3 C. The formula of Fe 3+ and O 2- is 3) Fe 2 O 3

Sample Problem 7-1 Write the formulas for the binary ionic compounds formed between the following elements:Write the formulas for the binary ionic compounds formed between the following elements: A. lithium and fluorine B. lithium and oxygen

Names of Variable Ions Use a roman number after the name of a metal that forms two or more ions Transition metals and the metals in groups 4A and 5A FeCl 3 (Fe 3+ ) iron (III) chloride CuCl (Cu + ) copper (I) chloride SnF 4 (Sn 4+ ) tin (IV) fluoride PbCl 2 (Pb 2+ )lead (II) chloride Fe 2 S 3 (Fe 3+ )iron (III) sulfide

II. Stock system (roman numerals) yExample: Fe 2+ Iron(II)Iron(II) Fe 3+ Iron(III)Iron(III) CuCl copper(I) chloridecopper(I) chloride CuCl 2 copper(II) chloridecopper(II) chloride

Sample Problem 7-2 a. Write the formula and give the name for the compound formed from the ions Cr 3+ and F -. b. Write the name for Cu 3 N 2.

Fe[Ar] 3d 6 4s 2 Fe 2+ [Ar] 3d 6 Fe 3+ [Ar] 3d 5 Here are the changes in the electronic structure of iron to make the 2+ or the 3+ ion.

Learning Check Complete the names of the following binary compounds with variable metal ions: FeBr 2 iron (_____) bromide Cu 2 Ocopper (_____) oxide SnCl 4 ___(_____ ) ______________ Fe 2 O 3 ________________________ CuS________________________

Solution Complete the names of the following binary compounds with variable metal ions: FeBr 2 iron ( II ) bromide Cu 2 Ocopper ( I ) oxide SnCl 4 tin (IV) chloride Fe 2 O 3 iron (III) oxide CuScopper (II) sulfide

Learning Check Name the following compounds: A. CaO 1) calcium oxide2) calcium(I) oxide 3) calcium (II) oxide B. SnCl 4 1) tin tetrachloride2) tin(II) chloride 3) tin(IV) chloride C. Co 2 O 3 1) cobalt oxide 2) cobalt (III) oxide 3) cobalt trioxide

Solution Name the following compounds: A. CaO1) calcium oxide B. SnCl 4 3) tin(IV) chloride C.Co 2 O 3 2) cobalt (III) oxide

Learning Check Write the correct formula for the compounds containing the following ions: A. Na +, S 2- 1) NaS 2) Na 2 S3) NaS 2 B. Al 3+, Cl - 1) AlCl 3 2) AlCl 3) Al 3 Cl C. Mg 2+, N 3- 1) MgN 2) Mg 2 N 3 3) Mg 3 N 2

Solution A. Na +, S 2- 2) Na 2 S B. Al 3+, Cl - 1) AlCl 3 C. Mg 2+, N 3- 3) Mg 3 N 2

Practise Na 2 O K 2 S MgBr 2 AlN Ba 3 As 2 CaCl 2 AgCl AlH 3 ZnI 2 Li 3 P Name the following ionic compounds:

Nomenclature of binary ionic compounds Na 2 O = sodium oxide K 2 S = potassium sulfide MgBr 2 = magnesium bromide AlN = aluminum nitride Ba 3 As 2 = barium arsenide CaCl 2 = calcium chloride AgCl = silver chloride AlH 3 = aluminum hydride ZnI 2 = zinc iodideLi 3 P = lithium phosphide Answers:

III. Polyatomic Ions zA charged group of covalently bonded atoms yCombine with ions of opposite charge to form ionic compounds zEx: NH 4 +, NO 3 -, SO 4 2-

Nomenclature of binary ionic compounds Some polyatomic anions that you must know: NO 3 - = nitrateNO 2 - = nitrite SO = sulfateSO 3 2- = sulfite PO 4 3- = phosphatePO 3 3- = phosphite CO 3 2- = carbonate HCO 3 1- = hydrogen carbonate or bicarbonate OH - = hydroxideCN - = cyanide C 2 H 3 O 2 - = acetateC 2 O 4 2- = oxalate

III. Polyatomic Ions zMost common ion is given the ending –ate. ClO 3 - chloratechlorate ClO 2 - chloritechlorite ClO - hypochloritehypochlorite ClO 4 - perchlorateperchlorate One less oxygen than –ate ends in –ite. One less oxygen than –ate ends in –ite. One less oxygen than –ite is given the prefix hypo. One less oxygen than –ite is given the prefix hypo. One more oxygen than -ate is given the prefix per. One more oxygen than -ate is given the prefix per. NO 3 - nitratenitrate NO 2 - nitritenitrite

Sample Problem 7-3 a. Write the formula for potassium sulfate. b. Write the formula for calcium carbonate. c. Write the formula for tin(IV) sulfate.

zpotassium chloride zmagnesium nitrate zcopper(II) chloride K + Cl  Mg 2+ NO 3  Cu 2+ Cl   KCl  Mg(NO 3 ) 2  CuCl 2 Ionic Nomenclature Practice

Nomenclature of binary ionic compounds NaHCO 3 K 2 SO 3 MgSO 4 KCN H 2 PO 4 Ca(OH) 2 NH 4 NO 3 Zn(NO 3 ) 2 Li 3 PO 4 HNO 3 Naming salts composed of the polyatomic ions is the same as with the monatomic anions. Metal name then polyatomic name. NaOH sodium hydroxide Ba(NO 3 ) 2 barium nitrate H 2 SO 4 hydrogen sulfate CsNO 2 cesium nitrite Sometimes there is a common name: KHCO 3 potassium hydrogen carbonate or potassium bicarbonate  Note: the polyatomic anions must be memorized. Name the following ionic compounds: