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Chemical Bonds. Octet Rule = atoms tend to gain, lose or share electrons so as to have 8 electrons. Gain 4 electrons. C would like to N would like to O would like to. Gain 3 electrons. Gain 2 electrons. Electron Dot Structures.
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Octet Rule = atoms tend to gain, lose or share electrons so as to have 8 electrons Gain 4 electrons • C would like to • N would like to • O would like to Gain 3 electrons Gain 2 electrons
Electron Dot Structures Symbols of atoms with dots to represent the valence-shell electrons 1 2 13 14 15 16 17 18 H He: LiBe B C N O : F :Ne : Na Mg AlSiPS: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.
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.
The coordination number of an ionic lattice is written as a ratio x:y How many chlorine ions surround each sodium ion and vice versa? NaCl coordination number- 6:6
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 CompoundsContain 2 different elements • Name the metal first, then the nonmetal as -ide. Examples: NaCl sodium chloride ZnI2 zinc iodide Al2O3 aluminum oxide
Practise Complete the names of the following binary compounds: Na3N ________________ KBr ________________ Al2O3 ________________ MgS _________________________
Solution Complete the names of the following binary compounds: Na3N sodium nitride KBr potassium bromide Al2O3 aluminum oxide MgS magnesium sulfide
Transition Metals Many form 2 or more positive ions 1+ 2+ 1+ or 2+ 2+ or 3+ Ag+ Cd2+ Cu+,Cu2+ Fe2+, Fe3+ silver cadmium copper(I) ion iron(II) ion ion ion copper (II) ion iron(III) ion Zn2+ zinc ion
Write symbols for these: • Potassium ion • Magnesium ion • Copper (II) ion • Chromium (VI) ion • Barium ion • Mercury (II) ion
Criss-Cross Method • Write the symbols for the ions side by side. Write the cation first. • Al3+ O2- • Cross over the charges by using the absolute value of each ion’s charge as the subscript for the other ion. • Al2 O3 • 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. • Al2O3 • For Al: 2 x 3+ = 6+ For O: 3 x 2- = 6-
Criss-Cross Method Example 1: Calcium and Oxygen O2- Ca2+ Ca2+ Calcium Ca2O2 O2- Oxide CaO
Criss-Cross Method Example 2: Magnesium and Phosphorus P3- Mg2+ Mg2+ Magnesium P3- Phosphorus Mg3P2 • 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 O2- is 1) NaO 2) Na2O 3) NaO2 2. The formula of a compound of aluminum and chlorine is 1) Al3Cl 2) AlCl2 3) AlCl3 3. The formula of Fe3+ and O2- is 1) Fe3O2 2) FeO3 3) Fe2O3
Solution A. The formula for the ionic compound of Na+ and O2- is 2) Na2O B. The formula of a compound of aluminum and chlorine is 3) AlCl3 C. The formula of Fe3+ and O2- is 3) Fe2O3
Sample Problem 7-1 • 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 FeCl3(Fe3+) iron (III) chloride CuCl (Cu+ ) copper (I) chloride SnF4 (Sn4+) tin (IV) fluoride PbCl2 (Pb2+) lead (II) chloride Fe2S3 (Fe3+) iron (III) sulfide
II. Stock system (roman numerals) • Example: Fe2+ Fe3+ • Iron(II) • Iron(III) CuCl2 CuCl • copper(I) chloride • copper(II) chloride
Sample Problem 7-2 a. Write the formula and give the name for the compound formed from the ions Cr3+ and F-. b. Write the name for Cu3N2.
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: FeBr2 iron (_____) bromide Cu2O copper (_____) oxide SnCl4 ___(_____ ) ______________ Fe2O3 ________________________ CuS ________________________
Solution Complete the names of the following binary compounds with variable metal ions: FeBr2 iron ( II ) bromide Cu2O copper ( I ) oxide SnCl4tin (IV) chloride Fe2O3iron (III) oxide CuS copper (II) sulfide
Learning Check Name the following compounds: A. CaO 1) calcium oxide 2) calcium(I) oxide 3) calcium (II) oxide B. SnCl4 1) tin tetrachloride 2) tin(II) chloride 3) tin(IV) chloride C. Co2O3 1) cobalt oxide 2) cobalt (III) oxide 3) cobalt trioxide
Solution Name the following compounds: A. CaO 1) calcium oxide B. SnCl43) tin(IV) chloride C. Co2O32) cobalt (III) oxide
Learning Check Write the correct formula for the compounds containing the following ions: A. Na+, S2- 1) NaS 2) Na2S 3) NaS2 B. Al3+, Cl- 1) AlCl3 2) AlCl 3) Al3Cl C. Mg2+, N3- 1) MgN 2) Mg2N3 3) Mg3N2
Solution A. Na+, S2- 2) Na2S B. Al3+, Cl- 1) AlCl3 C. Mg2+, N3- 3) Mg3N2
Practise Name the following ionic compounds: Na2O K2S MgBr2 AlN Ba3As2 CaCl2 AgCl AlH3 ZnI2 Li3P
Nomenclature of binary ionic compounds Answers: Na2O = sodium oxide K2S = potassium sulfide MgBr2 = magnesium bromide AlN = aluminum nitride Ba3As2 = barium arsenide CaCl2 = calcium chloride AgCl = silver chloride AlH3 = aluminum hydride ZnI2 = zinc iodide Li3P = lithium phosphide
III. Polyatomic Ions • A charged group of covalently bonded atoms • Combine with ions of opposite charge to form ionic compounds • Ex: NH4+, NO3-, SO42-
Nomenclature of binary ionic compounds Some polyatomic anions that you must know: NO3- = nitrate NO2- = nitrite SO4 2- = sulfate SO32- = sulfite PO43- = phosphate PO33- = phosphite CO32- = carbonate HCO31- = hydrogen carbonate or bicarbonate OH- = hydroxide CN- = cyanide C2H3O2- = acetate C2O42- = oxalate
III. Polyatomic Ions • Most common ion is given the ending –ate. • One less oxygen than –ateends in–ite. • One less oxygen than –iteis given the prefixhypo. • One more oxygen than -ateis given the prefixper. ClO3- ClO4- ClO2- ClO- • perchlorate • chlorate • chlorite • hypochlorite NO3- NO2- • nitrate • nitrite
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.
Ionic Nomenclature Practice • potassium chloride • magnesium nitrate • copper(II) chloride KCl • K+ Cl- • Mg2+ NO3- Mg(NO3)2 CuCl2 • Cu2+ Cl-
Nomenclature of binary ionic compounds Naming salts composed of the polyatomic ions is the same as with the monatomic anions. Metal name then polyatomic name. NaOH sodium hydroxide Ba(NO3)2 barium nitrate H2SO4 hydrogen sulfate CsNO2 cesium nitrite Sometimes there is a common name: KHCO3potassium hydrogen carbonate or potassium bicarbonate • Note: the polyatomic anions must be memorized. Name the following ionic compounds: NaHCO3 K2SO3 MgSO4 KCN H2PO4 Ca(OH)2 NH4NO3 Zn(NO3)2 Li3PO4 HNO3