1. Chapter 7.1 Chemical Formulas and Chemical Compounds
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. ions- atoms that have a charge
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. ions formed by single atom metals form ions by losing e-
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 –ide to 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. –ic ending indicates the higher charged ion
ex: Cu2+ cupric

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

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-

18. group of atoms covalently bonded with an overall charge
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. Write the name or the formula for the following: NH4OH lithium sulfate
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
dinitrogen pentoxide

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. HNO3 hydrogen nitrate (nitric acid)
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