Session Review Exam 3
Oxidation Numbers through Atomic Radii (plus anything needed from Exams 1 & 2)
Exam Topics
Guidelines for assigning oxidation numbers.
1. The oxidation number of any free, uncombined element is zero. 2. The oxidation number of an element in a simple (monatomic) ion is the charge on the ion. 3. In the formula for any compound, the sum of the oxidation numbers of all elements in the compound is zero. 4. In a polyatomic ion, the sum of the oxidation numbers of the constituent elements is equal to the charge on the ion.
Exam Topics
5. Fluorine has an oxidation number of 1 in its compounds. 6. Hydrogen, H, has an oxidation number of +1 unless it is combined with metals, where it has the oxidation number -1.
Examples LiH, BaH2 Exceptions: In peroxides O has oxidation number of 1.
Examples - H2O2, CaO2, Na2O2
7. Oxygen usually has the oxidation number -2.
In OF2 O has oxidation number of +2.
Exam Topics
8. Use the periodic table to help with assigning oxidation numbers of other elements.
a. IA metals have oxidation numbers of +1. b. IIA metals have oxidation numbers of +2. c. IIIA metals have oxidation numbers of +3.
There are a few rare exceptions.
d. VA elements have oxidation numbers of 3 in binary compounds with H, metals or NH4+. e. VIA elements below O have oxidation numbers of 2 in binary compounds with H, metals or NH4+.
Question 1
What is the oxidation number of phosphorus in Mg2P2O3? 1. +5 2. +3 3. +1 4. 0 5. -1 6. -3 7. -5
Exam Topics
Binary compounds are made of two elements.
metal + nonmetal = ionic compound nonmetal + nonmetal = covalent compound
Name the more metallic element first.
Use the element's name.
Name the less metallic element second.
Add the suffix "ide" to the element's stem.
Exam Topics
Binary ionic compounds containing metals that exhibit more than one oxidation state Metals exhibiting multiple oxidation states are:
1.most of the transition metals 2.metals in groups IIIA (except Al), IVA, & VA
Exam Topics
There are two methods to name these compounds. 1.Older method
add suffix "ic" to element's Latin name for higher oxidation state add suffix "ous" to element's Latin name for lower oxidation state
2.Modern method
use Roman numerals in parentheses to indicate metal's oxidation state
Exam Topics
Pseudobinary ionic compounds There are three polyatomic ions that commonly form binary ionic compounds.
1.OH- hydroxide 2.CN- cyanide 3.NH4+ ammonium
Exam Topics
Binary Acids are binary compounds consisting of hydrogen and a nonmetal. Compounds are usually gases at room temperature and pressure.
Nomenclature for the gaseous compounds is hydrogen (stem)ide.
When the compounds are dissolved in water they form acidic solutions.
Nomenclature for the acidic solutions is hydro (stem)ic acid.
Exam Topics
Binary covalent molecular compounds composed of two nonmetals other than hydrogen
Nomenclature must include prefixes that specify the number of atoms of each element in the compound.
Use the minimum number of prefixes necessary to specify the compound.
Frequently drop the prefix mono-.
Exam Topics
Ternary Acids and Their Salts are made of three elements.
The elements are H, O, & a nonmetal.
Two of the compounds are chosen as the basis for the nomenclature system.
Higher oxidation state for nonmetal is named (stem)ic acid. Lower oxidation state for nonmetal is named (stem)ous acid
Salts are named based on the acids.
Anions of -ic acids make "ate" salts. Anions of -ous acids make "ite" salts.
Exam Topics
There are two other possible acid and salt combinations. Acids that have a higher oxidation state than the "ic" acid are given the prefix "per".
These acids and salts will have one more O atom than the "ic" acid.
Acids that have a lower oxidation state than the "ous" acid are given the prefix "hypo".
These acids and salts will have one less O atom than the "ous" acid.
Exam Topics
Illustrate this series of acids and salts with the Cl ternary acids and salts. Acid Na Salt HClO NaClO
hypochlorous acid sodium hypochlorite
HClO2
chlorous acid
NaClO2
sodium chlorite
HClO3
chloric acid
NaClO3
sodium chlorate
HClO4
perchloric acid
NaClO4
sodium perchlorate
Exam Topics
Acidic Salts are made from ternary acids that retain one or more of their acidic hydrogen atoms.
Made from acid base reactions where there is an insufficient amount of base to react with all of the hydrogen atoms.
Old system used the prefix "bi" to denote the hydrogen atom. Modern system uses prefixes and the word hydrogen.
Exam Topics
Basic Salts are analogous to acidic salts.
The salts have one or more basic hydroxides remaining in the compound.
Basic salts are formed by acid-base reactions with insufficient amounts of the acid to react with all of the hydroxide ions. Use prefixes to indicate the number of hydroxide groups.
Exam Topics Redox Rxns
Oxidation is an increase in the oxidation number.
Corresponds to the loss of electrons.
Reduction is a decrease in the oxidation number.
Good mnemonic reduction reduces the oxidation number. Corresponds to the gain of electrons
Exam Topics
Oxidizing agents are chemical species that:
1. oxidize some other substance 2. contain atoms that are reduced in the reaction 3. gain electrons
Reducing agents are chemical species that:
1. reduce some other substance 2. contain atoms that are oxidized in the reaction 3. lose electrons
Exam Topics
Combination reactions occur when two or more substances combine to form a compound. There are three basic types of combination reactions.
1.Two elements react form to a new compound 2.An element and a compound react to form one new compound 3.Two compounds react to form one compound
Exam Topics
Decomposition reactions occur when one compound decomposes to form:
1.Two elements 2.One or more elements and one or more compounds 3.Two or more compounds
Exam Topics
Displacement reactions occur when one element displaces another element from a compound.
These are redox reactions in which the more active metal displaces the less active metal of hydrogen from a compound in aqueous solution. Activity series is given in Table 4-6
Exam Topics
Metathesis reactions occur when two ionic aqueous solutions are mixed and the ions switch partners.
AX + BY AY + BX
Metathesis reactions remove ions from solution in two ways:
1. form predominantly unionized molecules like H2O 2. form an insoluble solid
Ion removal is the driving force of metathesis reactions.
Exam Topics
A gas-formation reaction is a type of reaction in which there is a formation of an insoluble or slightly soluble gas when there are no gaseous reactants. Displacement reactions in which an active metal displaces from an acid or from water are gas-formation reactions; they are not methathesis reactions.
Exam Topics
Humphrey Davy in the early 1800's passed electricity through compounds and noted:
that the compounds decomposed into elements. concluded that compounds are held together by electrical forces.
Michael Faraday in 1832-1833 realized that the amount of reaction that occurs during electrolysis is proportional to the electrical current passed through the compounds
Exam Topics
J.J. Thomson modified the cathode ray tube experiments in 1897 by adding two adjustable voltage electrodes.
Studied the amount that the cathode ray beam was deflected by additional electric field.
Thomson used his modification to measure the charge to mass ratio of electrons.
Charge to mass ratio e/m = -1.75881 x 108 coulomb/g of e-
Thomson named the cathode rays electrons. Thomson is considered to be the "discoverer of electrons".
Exam Topics
In 1909 Millikan determined the charge and mass of the electron. Millikan determined that the charge on a single electron = -1.60218 x 10-19 coulomb. Using Thomson's charge to mass ratio we get that the mass of one electron is 9.11 x 10-28 g.
Exam Topics
Eugene Goldstein noted streams of positively charged particles in cathode rays in 1886. Particles move in opposite direction of cathode rays. Called "Canal Rays" because they passed through holes (channels or canals) drilled through the negative electrode. Canal rays must be positive. Goldstein postulated the existence of a positive fundamental particle called the "proton".
Exam Topics
Ernest Rutherford directed Hans Geiger and Ernst Marsden's experiment in 1910.
- particle scattering from thin Au foils Gave us the basic picture of the atom's structure.
In 1913 H.G.J. Moseley realized that the atomic number determines the element .
The elements differ from each other by the number of protons in the nucleus. The number of electrons in a neutral atom is also equal to the atomic number.
Exam Topics
James Chadwick in 1932 analyzed the results of -particle scattering on thin Be films. Chadwick recognized existence of massive neutral particles which he called neutrons.
Chadwick discovered the neutron.
Exam Topics
Mass number is given the symbol A. A is the sum of the number of protons and neutrons.
Z = proton number N = neutron number A=Z+N
A common symbolism used to show mass and proton numbers is A 48 E for example 12 C, 20 Ca, 197Au Z 6 79 Can be shortened to this symbolism .
14
N, Cu,
63
107
Ag, etc.
Exam Topics
The atomic weight of an element is the weighted average of the masses of its stable isotopes
Exam Topics
The wavelength of electromagnetic radiation has the symbol Wavelength is the distance from the top (crest) of one wave to the top of the next wave.
Measured in units of distance such as m,cm, . 1 = 1 x 10-10 m = 1 x 10-8 cm
The frequency of electromagnetic radiation has the symbol Frequency is the number of crests or troughs that pass a given point per second.
Measured in units of 1/time - s-1
Exam Topics
In 1900 Max Planck studied black body radiation and realized that to explain the energy spectrum he had to assume that:
1. energy is quantized 2. light has particle character
Planck's equation is
E h
or E
hc
h Planck' s constant
6.626 x 10-34 J s
Exam Topics
The Rydberg equation is an empirical equation that relates the wavelengths of the lines in the hydrogen spectrum.
1 1 R 2 n1 1 n2 2
7 -1
R is the Rydberg constant R 1.097 10 m n1 n 2 n' s refer to the numbers of the energy levels in the emission spectrum of hydrogen
Exam Topics
In 1925 Louis de Broglie published his Ph.D. dissertation.
A crucial element of his dissertation is that electrons have wavelike properties. The electron wavelengths are described by the de Broglie relationship
h mv h Planck' s constant m mass of particle v velocity of particle
Exam Topics
The principal quantum number has the symbol n.
The angular momentum quantum number has the symbol . The symbol for the magnetic quantum number is m. The last quantum number is the spin quantum number, ms.
Question
What is the electron configuration of Re (Rhenium)?
Exam Topics
Atomic radii describes the relative sizes of atoms. Atomic radii increase within a column going from the top to the bottom of the periodic table. Atomic radii decrease within a row going from left to right on the periodic table. This last fact seems contrary to intuition. How does nature make the elements smaller even though the electron number is increasing?