Transcript AP_Summer_Naming

Chemical Formulae
symbols, naming, writing formulae
Symbols and Formulae
118 known elements
ten million known compounds
elements - represented by chemical symbols (periodic
table)
compounds - represented by combos of chemical symbols
so we need a very concise naming system!
Some basics
cations vs anions
ions - electrically charged particle usually obtained
from an atom by adding or removing electrons
anion - negatively charged particle
gains/adds electrons
cation - positively charged particle
loses/removes electrons
monatomic ions - single atom with a charge
polyatomic ions - several atoms covalently bonded
but possessing an overall charge
Monatomic Naming
Cations
You should remember or revisit monatomic naming
handouts
cations are named by naming the element followed
by the word “ion” (i.e. calcium ion)
specific charges can be found on the periodic table
(see handout)
transition metals (gray boxes on handout) require
Roman numerals because these elements have
multiple oxidation numbers (charges):
value of charge = oxidation number
Monatomic Naming
Cations
CAUTION
Silver ion is always 1+ and does not require a
Roman numeral
Mercury (1) is Hg2+2 Mercury (II) Hg2+
Boron ion is B3+
Two polyatomic cations: ammonia (NH3+) and
hydronium (H3O+)
Monatomic Naming
Anions
There are monatomic anions and polyatomic anions
Monatomic anions are named by naming the element,
dropping the ending, and replacing with “-ide.”
Charges can be determined from the periodic table
(see handout).
Monatomic Naming
Anions
CAUTION (monatomic anions)
nitrogen, hydrogen, oxygen, and phosphorus lose
the last two syllables before adding “-ide”
oxide is O2- and peroxide is O22-
Polyatomic Anions
Polyatomic anions require a little work (see handout)
PLEASE learn the patterns for each group; they are
clearly explained to you in the handout titled
“Polyatomic Anions: The fifth level of the inferno”
If you know the “-ate” form of one member of each
group you will be able to determine the other forms
Suffix
General number of oxygen atoms
per- whatever -ate
1 more oxygen than “-ate”
whatever -ate
usually the most common form
whatever -ite
1 less oxygen than “-ate”
hypo- whatever -ite
1 less oxygen than “-ite”
Polyatomic Anions
There are special cases of polyatomic ions that must
be memorized, no trends! (see handout - 7th level)
acetate, cyanate, cyanide, hydroxide, oxalate,
peroxide
Polyatomic Anions
Sometimes there are prefixes with the polyatomic
ions, this is memorization of prefix meanings
bi- and hydrogen: hydrogen ion (H+) is added and
charge of polyatomic is changed
dihydrogen: two hydrogen ions are added and
charge is changed
di-: two polyatomic ions bonded AND one oxygen
atom is lost in the process (charge remains the
same)
thio-: replace an oxygen with a sulfur
Chemical Symbols
combo of symbols that represent the composition of
the compound
indicates the elements present and the relative
numbers of each element (subscripts)
Oxidation Numbers
predict oxidation number (charge on an atom) based
on stability
to determine the ratio of elements in a compound
when writing a chemical formula is to add charges
algebraically to equal zero
Ionic Compounds
compound/formula unit composed of cations and
anions
positive ion is ALWAYS written first
gives the smallest possible integer number of
different ions
parentheses enclose polyatomic ions when subscript
is greater than one
ionic substances are electrically neutral
Ionic Compounds
Examples: Write the ionic compound that results
from the combination of the following
• calcium and bromine: Ca2+ and Br- : CaBr2
•we need two bromines to balance the positive two charge of calcium
• aluminum and sulfate: Al3+ and SO42-: Al2(SO4)3
•we need two aluminums (@ 3+ each) to balance the three sulfates (@ 2- each)
Ionic
Compounds
Shortcut: Cross-and-Drop Method
charge of cation becomes subscript of anion
charge of anion becomes subscript of cation
•
Examples: Write the ionic compound that results
from the combination of the following
• chromium and oxygen: Cr3+ and O2-
•
Cr3+ O2-: Cr2O3
Ionic Compounds
Naming ionic compounds: name of metal followed by anion
name
Examples:
CaBr2 calcium bromide
CaCl2 calcium chloride
Al2(SO4)3 aluminum sulfate
Cr2O3 chromium oxide
SrO strontium oxide
Try these...
Write the formula and name of the ionic compound that
would result from the combination of the following ions
• 1. K+ CrO42• 2. Ca2+ O2-
• 3. Pb4+ Cr2O72• solutions:
•1. K2CrO4, potassium chromate
•2. CaO, calcium oxide
•3. Pb(Cr2O4)2, lead(IV) dichromate
Try these...
Write the ionic formula given the name of the
compound
• 1. iron(II) phosphate
• 2. titanium (IV) oxalate
• 3. thallium (III) nitrate
•solutions:
•1. Fe3(PO4)2
•2. Ti(C2O4)2
•3. Tl(NO3)3
Molecular Compounds
binary and organic
molecule - name given to covalently bonded
compounds; formed by neutral elements combining
diatomic molecules - made of two atoms of the same
element; there are 7 and they create a 7 on the
periodic table (hydrogen does not help make the “7” due
to placement)
•
H2, N2, O2, F2, Cl2, Br2, I2
Binary Molecular
Compounds
molecule composed of two elements; usually two
nonmetals, two metalloids, or a nonmetal and
metalloid
naming: use a prefix system
•1. name first element using exact element name
•2. name second element by writing stem of the
name
with the “-ide” ending
•3. add a Greek prefix to each element name to
denote the subscript of each element in formula
•(mono- is not usually used, unless needed to distinguish
two compounds of the same two elements, CO2 and CO)
Binary Molecular
Compounds
subscript
1
2
Greek prefixes
3
4
Oftentimes, the final
5
vowel of prefix is dropped
6
for ease in pronunciation
7
(i.e. heptaoxide and heptoxide)
8
9
10
prefix
monoditritetrapentahexaheptaoctanonadeca-
Binary Molecular
Compounds
Examples:
•N2O3: dinitrogen trioxide
•P4O6: tetraphosphorus hexoxide
•N2O4: dinotrogen tetroxide
•SF6: sulfur hexafluoride
•*note: the subscripts do not need to be the simplest ratio for
molecular compounds
Try these…
Write the formula or name the following:
• 1. Cl2O7
• 2. disulfur trichloride
• 3. SO3
• 4. CO2
• 5. carbon disulfide
• 6. CO
• solutions: 1. dichlorine hetpoxide; 2. S2Cl3; 3. sulfur
trioxide; 4. carbon dioxide; 5. CS2; 6. carbon
monoxide
Organic Molecular
Compounds (usually called just organic
compounds)
organic compounds - molecular substances that
contain carbon combined with other elements (H, O,
N…)
hydrocarbons - organic compounds that consist of
only carbon and hydrogen (hence the name!)
Organic Compounds
naming hydrocarbons
• 1. count the number of carbon atoms in the chain and select the
appropriate stem (see next slide)
• 2. add a suffix to indicate how the carbon atoms are attached
(single, double, or triple bonds)
•-ane (single bonds) CnH2n+2; n = number of carbon atoms,
number of hydrogen atoms is 2n+2
•-ene (double bond) CnH2n; n = number of carbon atoms,
number of hydrogen atoms is 2n
•-yne (triple bond) CnH2n-2; n = number of carbon atoms, number
of hydrogen atoms is 2n-2
• 3. combine prefix and suffix
Organic Compounds
IUPAC Hydrocarbon Prefixes
# of carbon atoms
prefix
1
meth-
2
eth-
3
prop-
4
but-
5
pent-
6
hex-
7
hept-
8
oct-
9
non-
10
dec-
11
undec-
12
dodec-
20
iscos-
Organic Compounds
Example: name the following
• C6H14
•1. C: 6 = hex
•2. H: 14 = 2n+2 = ane
•3. hexane
• C3H6
•1. C: 3 = prop
•2. H: 6 = 2n = ene
•3. propene
Organic Compounds
Examples: write the formula of the following
•octyne: C8H14
•methane: CH4 (understood 1 for C)
Try these...
Write the name or formula for the following:
• 1. C12H24
• 2. nonane
• 3. C20H42
• 4. ethene
• solutions: 1. dodecene; 2. C9H20; 3. icosane; 4. C2H4
Please Practice
There are several worksheets posted on moodle with
solutions, please take some time to review naming
concepts!
Please let me know of any difficulties or issues with
this Keynote, PowerPoint, or PDF (whichever you
select), thanks!