1. Single atoms of an element are at relatively high potential energy When atoms bond with others, resulting in electron sharing or electron transfer, this energy is lowered. This is why it is more likely to find calcium carbonate or calcium chloride than pure calcium metal in nature. Mullis1

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3. Writing Formulas for Ionic Compounds The positive ion comes FIRST. Write the charge of each ion over each symbol to help you decide subscripts. The total charges must add to 0. If the charges of the negative ion and positive ion are equal, this is the complete formula. K Cl KCl = potassium chloride CaSO 4 CaSO 4 = calcium sulfate 3 +1 +2-2

4. Writing the formula for an ionic compound One type of positive ion (cation) is combined with one type of negative ion (anion). The total positive charge from the ions must equal the total negative charge from the ions. Example: What is the formula for a compound made with strontium and bromine ions? 4 Sr 2+ Br -1 Charges do not cancel with only one of each atom Sr 2+ Br -1 +2 is now balanced by 2 x(-1) Formula is SrBr 2

5. Example 2: Ionic compound formula What is the formula for a compound made with strontium and phosphorous ions? 5 Sr 2+ P -3 Charges do not cancel with only one of each atom The common factor is 6. Sr 2+ +6 [3x(+2)] is now balanced by -6 [2x(-3)] Formula is Sr 3 P 2 Sr 2+ P -3

6. Writing Formulas When Ion Charge is Unequal The total charges must add to 0. The criss-cross method may be used to accomplish this: Mg Cl MgCl 2 Use subscripts to indicate how many ions are needed to make the compound. Use parentheses for polyatomics if there is more than one. MgNO 3 Mg(NO 3 ) 2 6 +2 +2

7. Charges: Determine from Periodic Table Group +1 ☺ H +2+3+3 -3-2 He LiBeBCNOFNe NaMg Transition Metals (Several + charges possible) AlSiPSClAr KCaScTiVCrMnFeCoNiCuZn (+2) GaGeAsSeBrKr RbSrAg (+1) Cd (+2) InSnSbTeIXe CsBaTlPbAtRn FrRa Mullis7

8. 8 Naming Compounds Binary Ionic Compounds Cation (+ charge ) is listed first. Name of cation is the chemical name. –For many transition metals, the ion is distinguished by the addition of a roman numeral after the chemical name. –Find charge of the anion and choose appropriate roman numeral to balance the charge. Name of the anion ends in –ide. Examples: Al 2 O 3 aluminum oxide CuBr 2 copper(II) bromide

9. Binary compound examples Write formula for potassium sulfide: K +1 + S 2-  K +1 + S 2-  K 2 S ( 2 x +1 ) = +2 charge for K and (1 x -2) = -2 charge for S Write formula for aluminum sulfide: Al +3 + S 2-  Al +3 + S 2-  Al 2 S 3 ( 2 x +3 ) = +6 charge for Al and (3 x -2) = -6 charge for S Write formula for magnesium sulfide: Mg +2 + S 2-  +2 and -2 cancel  MgS 9

10. Naming Compounds with Transition Metals The positive (+) charge of the metal is represented by a roman numeral in parentheses after the name. (I) = +1 (II) = +2(III) = +3 (IV) = +4 Cu 2+ and Cl - copper(II)chloride, or CuCl 2. Iron(III) chloride = FeCl 3, in which Fe has a 3+ charge To find the charge when you are given the formula, find the number needed to cancel out the negative charge in the compound. Mullis10

11. Mullis11 To find the charge when you are given the formula, find the number needed to cancel out the negative charge in the compound. Ex. 1. What is lead’s charge in PbCl 2 ? ? -1 Pb | Cl 2 totals | 2 x -1 = -2 +2 | -2 These must add to zero. Pb has +2 charge. The name of this compound is lead(II) chloride.

12. Mullis12 Example 2: What is the charge of copper in CuSO 4 ? SO 4 is the formula for the polyatomic ion, SO 4 2-. There is one SO 4 2- ion, so +2 is needed to cancel the -2 charge. Therefore the one copper atom has a +2 charge. The name of this compound is copper(II) sulfate. Example 3: Name Cr (NO 3 ) 3 chromium (?) nitrate +? | -1 x 3 +? | -3  the + charge must be 3 to cancel The compound name is chromium(III) nitrate.

13. Mullis13 Diatomics Di = two Atomic = atoms To achieve stability of 8 electrons in the outer shell of each atoms, these elements exist in pairs. Also kn0wn as the “Magnificent 7,” or BrINClHOF. NOF Cl Br I H N2N2 Br 2 I2I2 Cl 2 O2O2 H2H2 F2F2

14. Mullis14 Naming Molecular Compounds Binary Molecular Compounds If more than one atom, name the first element with a numerical prefix. –The first element is the farthest to left on periodic table. –If elements are in same group, name the lower one first. Name the second element with a numerical prefix and a suffix –ide. For prefixes, drop o or a if the element name begins with a vowel. (Examples are monoxide and pentoxide.) Exceptions: Do not use mono- for first element. Prefix is not needed for H as first element. Examples: N 2 O 4 dinitrogen tetroxide OF 2 oxygen difluoride

15. Mullis15 Numerical Prefixes: Use for Molecular compounds only! NumberPrefix 1mono- 2di- 3tri- 4tetra- 5penta- 6hexa- 7hepta- 8octa- 9nona- 10deca-

16. Mullis16 Polyatomic ions Poly = many Atomic = atoms Entire group of atoms is an ion with a positive or negative charge. Within the polyatomic ion, atoms are bound covalently. Examples: Sulfate ion SO 4 2- S Carbonate ion CO 3 2- C

17. Mullis17 Oxyanions: Polyatomics Containing Oxygen -ate: The most common form (ClO 3 - ) -ite: One less oxygen atom (ClO 2 - ) Per-: One more oxygen atom (ClO 4 - ) Hypo-: One less than –ite ion (ClO - ) Recall: Anion has negative charge. Anion of Cl is chloride.

18. Mullis18 Naming Acids Definition of Acid (for now): H + donor in H 2 O H is the cation in acids (again for now). Need enough H + ions to balance the charge of the anion. AnionAcidExample -idehydro____icHCl = hydrochloric acid -ate_________icH 2 SO 4 = sulfuric acid -ite_________ousHClO 2 = chlorous acid HClO = hypochlorous acid

19. Mullis19 Naming Acids Binary Acid = 2 elements (HCl) –Begin with hydro-. –Use name of 2 nd element and end with –ic. –HCl is hydrochloric acid. Oxyacid = H + O + 3 rd element (H 2 SO 4 ) –Usually incorporates the polyatomic ion name into the acid name. –Written with H first, then the polyatomic ion. –H 2 SO 4 is sulfuric acid.