Chemistry

1. Chemistry Chapter 7.1 Chemical Formulas and Chemical Compounds

2. Chemical Formulas • Elements- represented by symbols: shorthand method • JJ Berzelius given credit for establishing modern symbols • Symbols derived from name of element (Latin) • One letter= capitalized • O C F • Two letters= 1st capitalized, 2nd lowercase • He Hg Se

3. remember, atoms are electrically neutral (=# of e- and p) • elements form compounds sometimes by gaining e- or losing e- • forming ions • ions- atoms that have a charge • cation • anion

4. compounds are formed by a rxn between 2 or more elements • represented by combo of symbols called a chemical formula • represents composition (elements & # of atoms) • H2O C8H18 Al2(SO4)3

5. molecular comp- molecules • ionic comp- formula units • chemical formulas are exact & cannot be changed • represent amount of subst

6. Monatomic Ions • ions formed by single atom • metals form ions by losing e- • group 1 form ____ ions • group 2 form ____ ions • group 3 form ____ ions

7. nonmetals form ions by gaining e- • group 15 form _____ ions • group 16 form _____ ions • group 17 form ______ ions • group 18 form _____ ions

8. d block elements form 2+, 3+, or 1+ ions • cations are named by writing the elements name followed by ion • Na+ sodium ion

9. anions are named by dropping the ending of the element’s name, adding –ideto it, followed by ion • F- fluoride ion

10. Binary Ionic Compounds • in ionic compounds, ions must be combined so that the total positive and negative charges are equal • compounds composed of 2 different elements are binary compounds • to write formula: • write symbol for positive ion first, neg ion last • cross over the pos & neg values to give subscripts

11. aluminum and oxygen • calcium and iodine • magnesium and oxygen • ionic compounds are named by combining the names of the pos and neg ions • (don’t use words ion in name)

12. name previous examples

13. Nomenclature • methods of naming compounds • different names are used for positive ions that have 2 different charges: • Fabulous Five • 2 methods are used in the naming of these cations

14. Old System- Latin names for the elements are used a. –ous ending indicates the lower charged ion ex: Cu+ cuprous b. –icending indicates the higher charged ion ex: Cu2+ cupric

15. ex: Cu+ O2- • name: • Cu2+ O2- • name:

16. 2. stock system- actual charge of the ion is given as a Roman numeral Cu+ copper I ion Cu2+ copper II ion

17. Cu+ O2- • name: • Cu2+ O2- • name:

18. Polyatomic Ions • group of atoms covalently bonded with an overall charge • almost all are neg charged • almost all are oxyanions- polyatomic ions that contain oxygen

19. several cases where 2 different oxyanions are formed by the same element • NO3- NO2- • to distinguish between them, the ion w/ the larger # of oxygen atoms is named w/ an –ate ending

20. the ion w/ the lower # of oxygen atoms is named w/ an –ite ending SO42- SO32- name compounds containing polyatomic ions in same manner as binary ionic comp

21. to write the formulas: 1. metal cation written first, followed by polyatomic ion 2. cross over values to become subscripts 3. when more than 1 polyatomic ion is present, parentheses are used & a subscript is put outside the ()

22. lithium nitrate • barium phosphate • aluminum sulfite

23. Pop Quiz Write the name or the formula for the following: • NH4OH • lithium sulfate • Cu2O • hydrogen sulfide • FePO4 (old way)

24. Binary Molecular compounds • compounds betw nonmetals • since molecular, ionic charges are not used to assign formulas or names to the compounds • prefixes are used to tell how many atoms of ea element are present in ea molecule

25. RULES: 1. use a prefix w/ the name of the 1st element only if it has more than one atom present 2. name the 2nd element by combining a prefix (if > 1 compound can be formed by the 2 elements) w/ the root of the name and the –ide ending write the least EN element first

26. phosphorus trichloride • carbon tetrachloride • dinitrogenpentoxide

27. Acids and Salts • 2 groups;: 1. binary acids- soln in H2O containing H and one of the halogens ex: HCl hydrogen chloride or hydrochloric acid

28. 2. oxyacids- acids containing H, O , and a 3rd element HNO3 hydrogen nitrate (nitric acid) HNO2 hydrogen nitrite (nitrous acid)

29. Naming Organic Compounds • hydrocarbons- simplest group of organic compounds • composed of H and C only • ex; CH4 C2H6 • carbon can have 4 bonds w/ other elements or other C atoms • C atoms can link to elements or other atoms in chains or rings

30. Naming Compounds 1. when naming org comp, 1st count how many C atoms in comp determines the stem of the name 2. add to the stem the suffix -ane

31. 3. if the C atoms are attached in a ring, the prefix cyclo- is added to the stem and ane draw structural formulas write chemical formulas

32. Hydrocarbon Stems # C atoms/Stem • meth- • eth- • prop- • but- • pent- • hex- • hept- • oct- • non- • dec-

33. Oxidation Numbers • oxidation # (or states) are assigned to atoms in molecules (including molecular ions) to show the general distribution of e- among bonded atoms • the more EN atom in bond has been assigned ownership of e-

34. very useful in naming compounds & writing formulas • F most EN element = has assigned ox # of -1 in every comp • O is 2nd most EN usu has an ox # of -2 in most comp • Elements with most EN are written to the right of formula (they attract e-) • oxidation # is the charge the atom would posses if the bonding were ionic

35. RULES: • ox # of an element in elemental form is 0 • ox # of monatomic ion is the same as its ionic charge • in binary compounds, the element w/ the greater EN is assigned a neg ox# equal to its charge in simple ionic compounds • the sum of the ox #s is = 0 for an electrically neutral compound & = to charge on polyatomic ion

36. ox #exhibit periodic trends • H has ox # of +1 when it is bonded to more EN element • ex: HCl • H has a neg 1 ox # when it is bonded to a less EN element • ex: NaH