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Lab Today! Bring Prelab, Lab print out, goggles, calculator.
WEAR THE CORRECT ATIRE!!!!!!!!
Exam M through however far we get today….
Problem: Calculate the abundance of the two Bromine isotopes: 79Br = 78.918336 amu and 81Br = 80.91629 amu , given that the average mass of Bromine is 79.904 amu.
Plan: Let the abundance of 79Br = X and of 81Br = Y and X + Y = 1.0
Solution: X(78.918336) + Y(80.91629) = 79.904
X + Y = 1.00 therefore X = 1.00 - Y (1.00 - Y)(78.918336) + Y(80.91629) = 79.904
78.918336 - 78.918336 Y + 80.91629 Y = 79.904
1.997954 Y = 0.985664 or Y = 0.4933
X = 1.00 - Y = 1.00 - 0.4933 = 0.5067
%X = % 79Br = 0.5067 x 100% = 50.67% = 79Br %Y = % 81Br = 0.4933 x 100% = 49.33% = 81Br
Modern Reassessment of the Atomic Theory
1. All matter is composed of atoms. Although atoms are composed of smaller particles (electrons, protons, and neutrons), the atom is the smallest body that retains the unique identity of the element.
2. Atoms of one element cannot be converted into atoms of another element in a chemical reaction. Elements can only be converted into other elements in Nuclear reactions in which protons are changed.
3. All atoms of an element have the same number of protons and electrons, which determines the chemical behavior of the element. Isotopes of an element differ in the number of neutrons, and thus in mass number, but a sample of the element is treated as though its atoms have an average mass.
4. Compounds are formed by the chemical combination of two or more elements in specific ratios, as originally stated by Dalton.
Definitions
• ELEMENT - A substance that cannot be separated into simpler substances by chemical means
• COMPOUND - A substance composed of atoms of two or more elements chemically united in fixed proportions
• PERIODIC TABLE - “MENDELEEV TABLE” - A tabular arrangement of the elements, vertical groups or families of elements based upon their chemical properties - actually combining ratios with oxygen
Fig. 2.16
Metal
A substance or mixture that has a characteristic luster or shine and is generally a good conductor of heat and electricity
Nonmetal
An element that does not exhibit the characteristics of a metal
Metalloid
An element having characteristics of both metals and nonmetals
Fig. 2.17
A period consists of the elements in one horizontal row.
A group consists of the elements in one vertical column.
Groups are numbered using two systems:IUPAC Numbers 1 through 18
Older system Roman numerals I–VIII and the letters A and B
Groups in the Periodic Table
Main Group Elements (Vertical Groups) Group IA - Alkali Metals Group IIA - Alkaline Earth Metals Group IIIA - Boron Family Group IVA - Carbon Family Group VA - Nitrogen Family Group VIA - Oxygen Family (Calcogens) Group VIIA - Halogens Group VIIIA - Noble GasesOther Groups ( Vertical and Horizontal Groups)Group IB - 8B - Transition MetalsPeriod 6 Group - Lanthanides (Rare Earth Elements)Period 7 Group - Actinides
O
S
Se
Te
Po
N
P
As
Sb
Bi
C
Si
Ge
Sn
Pb
B
Al
Ga
In
Tl
ZnCu
Cd
Hg
Ag
Au
Ni
Pd
Pt
Co
Rh
Ir
Fe
Ru
Os
Mn
Tc
Re
Cr
Mo
W
V
Nb
Ta
Ti
Zr
Hf
Sc
Y
La
Ac
The Periodic Table of the Elements
The Alkali Metals
The Alkaline Earth Metals
Ce Pr Nd PmSmEu Gd Tb Dy Ho Er TmYb Lu
Th Pa Np PuAmCmBk Cf Es FmMd No LrU
H
Li
Na
K
Rb
Cs
Fr
Be
Mg
Ca
Sr
Ba
Ra Rf Sg
The Halogens
The Noble Gases
He
Ne
Ar
Kr
Xe
Rn
F
Cl
Br
I
At
Du Bo HaMe
Figure 2.14: A modern form of the periodic table.
Chemical Compounds and Bonds
Chemical Bonds - The electrostatic forces that hold the atoms of elements together in the compound.
Ionic Compounds - Electrons are transferred from one atom to another to form Ionic Cpds.
Covalent Compounds - Electrons are shared between atoms of different elements to form Covalent Cpds.
“Cations” - Metal atoms lose electrons to form “ + ” ions.
“Anions” - Nonmetal atoms gain electrons to form “ - ” ions.
Mono-atomic ions form binary ionic compounds
Figure 2.16: Molecular and structural formulas and molecular models for some compounds.
• An ionic compound is composed of cations and anions.
• Ions are arranged in a repeating three-dimensional pattern, forming a crystal.
• The formula of an ionic compound gives the smallest possible integer number of ions in the substance (without writing charges) so that the combination is electrically neutral.
• The formula gives the formula unit of the compounds. A formula unit is not a molecule!
Fig. 2.18
Figure 2.19: A model of a portion of NaCl.
He
Ne
Ar
Kr
Xe
Rn
The Periodic Table of the Elements
Most Probable Oxidation State
Cr Mn Fe Co Ni
Mo
W
Tc
Re
Ru
Os
Rh
Ir
Pd
Pt
+1
+2
+3 +4
+3 +_4 - 3 - 2 - 1
0
H
Li
Na
K
Rb
Cs
Fr
Sc
Y
Be
Mg
Ca
Sr
Ba
Ra
La
Ac
B
Al
Ga
In
Tl
Ti
Rf
Hf
Zr
C
Si
Ge
Sn
Pb
F
Cl
Br
I
At
O
S
Se
Te
Po
N
P
As
Sb
Bi
Zn
Cd
Hg
+ 2+1
Cu
Ag
Au
+5
V
Nb
Ta
Ce
Th
Pr Nd Pm Sm Eu Gd Tb Dy Ho Er Tm Yb Lu
Pa U Np Pu Am Cm Bk Cf Es Fm Md No Lr
+3
+3
Du Sg Bo Ha Me
Fig. 2.20
Fig. 2.19
• What is formula of the ionic compound of Mg2+ and N3-?
• The common multiple of the charges is 6, so we need three Mg2+ and two N3-. The resulting formula is
• Mg3N2
• What is the formula of the ionic compound of Ca2+ and PO4
3-?
• The common multiple of the charges is 6, so we need three Ca2+ and two PO4
3-. The resulting formula is
• Ca3(PO4)2
• Organic Compounds
• An important class of molecular substances; they contain carbon combined with other elements – notably hydrogen, oxygen, and nitrogen.
• Hydrocarbons contain only carbon and hydrogen.
• A functional group is a reactive portion of a molecule that undergoes predictable reactions.
•Examples•Name of Group
•Functional Group
•Methyl alcohol•AlcoholOH
•Dimethyl ether•EtherO
•Acetic acid•Carboxylic acid
C
O
OH
Figure 2.23: Molecular model of nitric acid.
What is the formula for nitric acid?
HNO3
• Chemical nomenclature is the systematic naming of chemical compounds.
• Compounds that are not organic are called inorganic compounds.
Carbon monoxide, carbon dioxide, carbonates, and cyanides are also classified as inorganic compounds.
• Naming Inorganic Compounds
1.Name the cation.
2.Name the anion.
• 2. Some main-group metals with high atomic number have more than one cation. One cation will have the charge of the group number minus 2; the second cation will have a charge equal to the group number
Pb in Group IVA(14) has two ions:
Pb2+ and Pb4+
Tl in Group IIIA(13) has two ions:
Tl+ and Tl3+
• 3. Most transition metals form more than one cation, of which one is +2.Zn and Cd form only the +2 ion.
Ag forms only the +1 ion.
• 4. Nonmetal main-group elements form one monatomic anion with a charge equal to the group number minus 8.F in Group VIIA(17) forms the F- ion.
S in Group VIA(16) forms the S2- ion.
N in Group VA(15) forms the N3- ion.
• Naming Monatomic Ions
• Monatomic cations are named after the element if the element forms only one cation.
• If more than one cation forms:
a.In the Stock system, the charge is written using a Roman numeral and is enclosed in parentheses.
Cu2+ is copper(II).
Cu+ is copper(I).
• Fe3+ is iron(III)• Fe2+ is iron(II)
• Hg2+ is mercury(II).• The second ion mercury forms is diatomic:
Hg22+ is mercury(I).
• Cr3+ is chromium(III).• Cr2+ is chromium(II).
• Mn2+ is manganese(II).• Co2+ is cobalt(II).
• Zinc forms only Zn2+, so it is called zinc ion.• Cadmium forms only Cd2+, so it is called
cadmium ion.• Silver forms only Ag+, so it is called silver ion.
• Polyatomic Ion
• An ion consisting of two or more atoms chemically bonded together and carrying an electrical charge.
• Table 2.5 lists common polyatomic ions.
• Cations
• mercury(I) or mercurous Hg22+
• ammonium NH4+
• Anions
• peroxide O2-
• hydroxide OH-
• cyanide CN-
• phosphate PO43-
• monohydrogen phosphate HPO42-
• dihydrogen phosphate H2PO4-
• carbonate CO32-
• bicarbonate HCO3-
• sulfate SO42-
• bisulfate HSO4-
• sulfite SO32-
• bisulfite HSO3-
acetate C2H3O2-
oxalate C2O42-
chromate CrO42-
dichromate Cr2O72-
permanganate MnO4-
nitrate NO3-
nitrite NO2-
hypochlorite ClO-
chlorite ClO2-
chlorate ClO3-
perchlorate ClO4-
• What are the names of the following ionic compounds?
– BaO
– Cr2(SO4)3
BaO is barium oxide.Cr2(SO4)3 is chromium(III) sulfate or chromic sulfate.
• What are the chemical formulas for the following ionic compounds?
– potassium carbonate
– manganese(II) sulfateThe ions K+ and CO3
2- form K2CO3
The ions Mn2+ and SO42- form MnSO4
• Binary Molecular Compounds
• A compound composed of only two elements.
• Binary compound of a metal and a nonmetal are generally named using ionic rules.
• Naming Binary MolecularMolecular Compounds
• We usually name the elements in the order given in the formula.
• Name the first element using the element name.
• Name the second element using the element root + -ide suffix.
• Add a prefix to each name to indicate the number of atoms of that element. The prefix mono- is used only when needed to distinguish two compounds of the same two elements.
• The final vowel of the prefix is often dropped when followed by an element name that begins with a vowel. Oxygen is the most common example.N2O4 dinitrogen tetroxide (“a” is dropped)
NO nitrogen monoxide (only one “o”)
(also called nitric oxide)
Don’t use thesewhen naming ioniccompounds--they’reONLY for covalentcompounds!!
• Some compounds have common names that differ from their systematic names:
H2S hydrogen sulfide (the “di” is omitted)
H2O water
NH3 ammonia
• Common names need to be memorized.
• What are the names of the following compounds?
– OF2
– S4N4
– BCl3
OF2 is oxygen difluoride
S4N4 is tetrasulfur tetranitride
BCl3 is boron trichloride
• What are the formulas for the following binary molecular compounds?
– carbon disulfide
– nitrogen tribromide
– dinitrogen tetrafluorideThe formula for carbon disulfide is CS2.
The formula for dinitrogen tetrafluoride is N2F4.
The formula for nitrogen tribromide is NBr3.
• Acids and Corresponding Anions
• Oxoacids contain hydrogen, oxygen, and a third central atom.
To name an acid from its anion name:1. Change an –ate suffix to –ic.2. Change an –ite suffix to –ous.3. Add the word “acid.””
• For example:HNO3 nitric acid
H2SO4 sulfuric acid
Figure 2.23: Molecular model of nitric acid.
What is the formula for nitric acid?
HNO3
• Bromine has an oxoacid, HBrO2, bromous
acid (compare to HClO2, chlorous acid). What are the name and formula of the corresponding anion?
The anion corresponding to HBrO2 isbromite, BrO2
-.
• Hydrate
• A compound that contains water molecules weakly bound in the crystals.
• The formula of a hydrate is written with a dot before the water molecule(s) included.
• For example:CuSO45H2O
• Hydrates are named using the anhydrous (without water) compound name followed by the prefix for the number of water molecules included and the word “hydrate.”
• For example:CuSO45H2O is named
copper(II) sulfate pentahydrate.
• A compound whose common name is green vitriol has the chemical formula FeSO47H2O. What is the chemical name of this compound?
FeSO47H2O is iron(II) sulfate heptahydrate.
• Calcium chloride hexahydrate is used to melt snow on roads. What is the chemical formula of the compound?
The chemical formula for calcium chloride hexahydrate is CaCl26H2O.
• A chemical equation is the symbolic representation of a chemical reaction in terms of chemical formulas.
• For example: 2Na + Cl2 2NaCl
• Reactants are the starting materials; they are written on the left of the equation.
• Products are the materials at the end of the reaction; they are written on the right of the equation.
• Because a reaction must accurately describe the chemical reaction, it must be consistent with the law of conservation of mass.
• When this is not the case, after correct formulas are written for each reactant and product, the coefficients are adjusted so that the same number of each atom is present in both the reactants and the products.
• This is called balancing the equation.
• For example, the reaction of sodium with chlorine produced sodium chloride.
• First, we determine the correct formula for each compound.
Sodium is Na.
Chlorine is Cl2.
Sodium chloride is NaCl.
Second, we write the reaction.
Na + Cl2 NaCl
• Third, we check the number of each atom on each side of the equation.
• This equation shows two Cl atoms on the reactant side and only one Cl atom on the product side. To balance the Cl atoms, we insert a coefficient of “2” before NaCl on the product side.
Na + Cl2 2NaCl
Na + Cl2 2NaCl
• Now the Na are not balanced: there is one on the reactant side and there are two on the product side. To balance Na, we insert the coefficient “2” before Na on the reactant side.
2Na + Cl2 2NaCl
• The reaction is now balanced!
• Balance the following equation:
• CS2 + O2 CO2 + SO2
Tally the number of each atom on each side:C 1 on reactant side; 1 on product sideS 2 on reactant side; 1 on product sideO 2 on reactant side; 4 on product side
Begin by inserting the coefficient “2” before SO2 on the product side. We leave O2 until later because it is an element.
• CS2 + O2 CO2 + 2SO2
• Tally the atoms again:
• C 1 on reactant side; 1 on product side
• S 2 on reactant side; 2 on product side
• O 2 on reactant side; 6 on product side
• Insert a “3” before O2:
• CS2 + 3O2 CO2 + 2SO2
• CS2 + 3O2 CO2 + 2SO2
• Tally the atoms again:
• C 1 on reactant side; 1 on product side
• S 2 on reactant side; 2 on product side
• O 6 on reactant side; 6 on product side
• The reaction is now balanced!
• Balance the following equation:
• NH3 + O2 NO + H2OTally the number of each atom on each side:
N 1 on reactant side; 1 on product sideH 3 on reactant side; 2 on product sideO 2 on reactant side; 2 on product side
Begin by inserting the coefficient “2” before NH3 on the reactant side and the coefficient “3” before H2O on the product side. We leave O2 until later because it is an element.
• 2NH3 + O2 NO + 3H2O
• Tally the atoms again:
• N 2 on reactant side; 1 on product side
• H 6 on reactant side; 6 on product side
• O 2 on reactant side; 4 on product side
• To balance N, insert a “2” before NO:
• 2NH3 + O2 2NO + 3H2O
•2NH3 + O2 2NO + 3H2O
•Tally the atoms again:N 2 on reactant side; 2 on product side
H 6 on reactant side; 6 on product side
O 2 on reactant side; 5 on product side
•Since this gives us an odd number oxygens, we double the coefficients on NH3, NO, and H2O and to balance O, insert a “5” before O2.
Tally the atoms again to double check:
4NH3 + 5O2 4NO + 6H2O
N 4 on reactant side; 4 on product side
H 12 on reactant side; 12 on product side
O 10 on reactant side; 10 on product side
•The reaction is now balanced!
• Balance the following equation:
• C2H5OH + O2 CO2 + H2O
Tally the number of each atom on each side:C 2 on reactant side; 1 on product sideH 6 on reactant side; 2 on product sideO 3 on reactant side; 3 on product side
Begin by balancing H. Insert the coefficient “3” before H2O on the product side. We leave O2 until later because it is an element.
• C2H5OH + O2 CO2 + 3H2O
• Tally the number of each atom on each side:
• C 2 on reactant side; 1 on product side
• H 6 on reactant side; 6 on product side
• O 3 on reactant side; 5 on product side
• To balance C, insert a “2” before CO2.
