UNIT 0:
Nomenclature: Ionic Compounds, Molecular Compounds, Acids & Bases, & Simple Organic Molecules
The Periodic Table
· You can identify elements by their atomic number, which can be read off the periodic table.
History
Ø Dimitri Mendeleev noticed a periodicity in the properties when elements were arranged in increasing atomic mass
Ø GJ Moseley reformed the hypothesis to state that periodic properties are functions of increasing atomic number
Organization
Ø Period- horizontal rows (7 of them)
Ø Group – vertical columns also called families
ü Groups are numbered from 1-18 starting at left
ü Group numbers of representative elements or main group elements are 1,2,13-18
ü Transition elements are in the center of the periodic table; groups 3 – 12; they contain many elements with more than 1 charge(multi-valent)
ü Groups can also be numbered with a letter
A elements are called representative element or main group
B elements are called transition elements; all metallic solids
ü Groups with special names
Alkali metals: group 1 or 1A
properties- react vigorously with water to produce hydrogen gas & alkaline
solutions, all metals, all solids, always combined, easily lose 1 valence
electron; form +1 ions
Alkaline earth metals: group 2 or 2A
properties- reactive but not as strong as 1A all metals; all solids; form
alkaline solutions, lose 2 valence electrons, forms +2 ions
Halogens: group 17 or 7A
properties: very reactive nonmetals, react with alkali metals to form salts,
F,Cl, I, Br are diatomic, gains 1 valence electron, forms -1 ions
Noble gases (rare or inert): group 18 or 8A properties- does not react with
any other substances, all gases, stable, does not form ions
Metals, Nonmetals, and Metalloids
ü diagonal line or stair way starts to the left of boron separates the metals from the nonmetals
ü metals are great conductors of heat &electricity, mostly solids, high luster, malleable, ductile, and form alloys
ü nonmetals are poor conductors, dull & brittle, mostly gases and liquids
ü metalloids lie to the immediate right or left of the stairway with the exception of Al share properties of metals and nonmetals
B, Si, Ge, As, Sb, Te, Po, and At are the 8 metalloids
Chemical Formulas
A. Shorthand way of expressing compounds by using a symbol for the element and a subscript for the number of atoms
Molecular formula: shows the exact number of atoms of each element in the smallest unit of a substance
Ø Molecules are 2 or more atoms of the same or different nonmetal elements covalently bonded together; act as discreet units: C6H6
Ø Diatomic Molecules contain only 2 atoms (Professor BrINClHOF references the diatomic elements): H2, N2, O2, Br2, F2, I2, Cl2, Br2, HCl, CO
Ø Covalent bonding occurs when valence electrons are shared between 2 nonmetal atoms
Ø Forces between neighboring molecules are usually weak in comparison to ionic bonding
Empirical formula: shows the simplest whole-number ratio of the atoms in a substance
Ø Ions are charged particles formed when an atom or group of atoms gain or lose electrons
Ø Cations are positively charged ions formed from metals that lose electrons example: Na+1
Ø Anions are negatively charged ions formed from nonmetals that gain electrons example: Cl-1
Ø Ionic Bonding occurs when the oppositely charged ions are electrostatically attracted to each other: example NaCl
Ø Forces between neighboring formula units are usually stronger than between molecules
MUST KNOW!
1. Molecule: bonded set of 2 or more atoms of the same or different atoms: H2 , CO2
2. Atom: a single unit of an element: Au or Pb
3. Ion- an atom or group of atoms that have a net positive or negative charge; CO32- ,S 2-
Monatomic ions are single atoms that have lost or gained electrons
For main group elements, the charges of the ions formed by the atoms can be
predicted by applying this principle:
ü Atoms that are close to a noble gas (the nonmetals) form ions that contain the same number of electrons as the neighboring noble gas atom.
ü Metals of group 1A –3A form positive ions with a charge equal to the group number
ü Transition metals- no predictable pattern; have several different ion
charges
Ø are in groups 3 –112
Ø These cations typically have charges of +1, +2, or +3.
ü Nonmetals form ions with a negative charge equal to (8 minus the group
number)
ü Some common charges of ions formed by the main group elements
Ø group 1 : +1
Ø group 2 : +2
Ø Al in group 13: +3
Ø N in group 15: -3
Ø group 16: -2
Ø group 17: -1
Ø H can either gain or lose electrons; H+1 or H-1
ü Valence electrons- electrons in the outermost shell of an atom
Polyatomic Ions
ü 2 common polyatomic cations are NH4+1 and Hg2+2.
ü Polyatomic ions usually have 1 or more oxygen atoms. These are collectively called oxyanions.
ü Memorize the name, formula and charge of the polyatomic. Most polyatomic ions contain one or more oxygen atoms. Rules for naming oxyanions:
Ø The suffix -ate is used for the anion with the larger number of oxygen atoms
Ø The suffix -ite is used for the anion containing fewer oxygen atoms
Ø The prefix hypo- is used when the oxyanion has more than 2 forms: it means the fewest oxygen atoms
Ø The prefix per- is used when the oxyanion has more than 2 forms: it means the largest number of oxygen atoms.
Naming and Writing Formulas for Ionic Compounds
ü Ionic Compounds must have electrical neutrality : the total positive charge of the cations in the formula must equal the total negative charge of the anions.
Na+1 and S-2 must be written as Na2S since you need 2 positive charges to balance the –2 charge on the S.
ü The formula for an ionic compound shows the simplest whole number ratio between cation and anion. This is always an empirical formula.
ü Ions are arranged in a 3D network called a crystal lattice.
Rules for Writing Formulas
ü There must electrical neutrality.
ü The positive ion is always written before the negative ion.
ü If 2 or more polyatomic ions are used in the formula, enclose the polyatomic ion
in parentheses and put the number of ions you need outside the parentheses as a subscript.
ü Do not write the charge of the ion in the formula. sodium sulfide is Na2S, not Na+2S-2
ü Remember Criss Cross Method of determining subscripts
Examples: Write chemical formulas for the following:
aluminum oxide calcium bromide
sodium carbonate
Rules for Naming Ionic Compounds
ü When a metal is involved, the name of the metal is used.
ü When the metal ion can have 2 different charges (usually group B or Sn & Pb), the charge of the ion is indicated by writing it in Roman numerals in parentheses after the name of the metal. ie. Cu+1 is copper (I)
ü When a nonmetal is involved, -ide is added as a suffix to the root word of the nonmetal (usually the first syllable); i.e. bromine becomes bromide
ü Polyatomic ions retain their special name.
Examples: Name the following ionic compounds
BaCl2 K2O Mg(OH)2
KNO3 FeCl3 SnO
Naming and Writing Formulas for Covalent Compounds
ü Nonmetals combine in various ratio to form neutral molecules
ü There are no charges in a molecule
Naming Binary Molecular (Covalent) Compounds
ü The first nonmetals get its full name. The second nonmetal gets its root word + - ide ending.
ü Both nonmetals get a prefix denoting how many atoms are used to make the compound. However, when only 1 atom is used, the prefix mono is not attached in the first part of the binary compound.
ü For Example: CO2 is carbon dioxide
ü Prefixes: mono (1) di (2) tri (3) tetra (4) penta (5)
hexa (6) hepta (7) octa (8) nona (9) deca (10)
Examples: Write the names for the following covalent compounds
HI NF3 SO2
N2Cl4 NO2
Acids
ü Defined as a substance that yields H+1 ions when dissolved in water
ü When the gaseous binary molecules form acidic aqueous solutions, the -ide suffix is changed to -ic. and the prefix hydro- is used.
Examples: Name the following binary acids
HCl H2S
ü When a hydrogen ion combines with an oxyanion like PO4-3, an oxyacid is formed. The prefixes of the oxyanion, per, and hypo remain unchanged. The suffix -ate is changed to -ic and the suffix -ite is changed to -ous.
ü i.e. HClO3 is choric acid.
Examples: Name the following acids
HNO3 H2CO3 H2SO4
H3PO3
Bases
ü Defined as a substance that yields OH-1 ions when dissolved in water
ü Most of the bases you will use are metal hydroxides(ionic compounds) or NH3
ü There are lots of organic bases but you do not need to be too familiar with these
Examples: Name the following bases
Sr(OH)2 Fe(OH)3
Mixed Practice: Decide whether each compound is an ionic compound, molecular compound, acid or base and write its formula. Use flow chart above!
1.Dinitrogen monoxide 2.Potassium sulfide
3.Copper (II) nitrate 4.Dichlorine heptoxide
5.Chromium (III) sulfate 6.Ferric sulfite
7.Calcium oxide 8.Barium carbonate
9.Iodine monochloride
Decide whether each compound is an ionic compound, molecular compound, acid or base and write its name
1.BaI2
2.P4S3
3.Ca(OH)2
4.CoCO3
5.Na2Cr2O7
6.I2O5
7.Zn(ClO4)2
8.CS2
9.B2Cl4
Organic Nomenclature
ü Compounds containing carbon; over 6 million compounds; vital to living things and important in daily life
ü can contain other elements such as hydrogen, nitrogen, sulfur, phosphorus, oxygen and the halogens
ü Have relatively low melting points, low boiling points, high solubility in other organic substances rather than water, and poor conductivity
Types of Formulas
ü Molecular Formulas: indicate the type & number of each atom in the compound
C4H10
ü Structural Formula: indicates the complete 2D structure of the compound showing the bonds
ü Condensed Structural formulas: shorthand representation that leaves the bond lines out but indicates what is bonded to each carbon or other atoms.
CH3CH2CH2CH3
Hydrocarbons
ü organic compounds that contain only hydrogens and carbons.
ü Prefixes used in naming:
1- meth 2-eth 3-prop 4-but 5-penta 6-hexa
7- hepta 8-octa 9- nona 10-deca 11- undeca 12- dodeca
Alkanes (CnH2n+2)
ü saturated hydrocarbon chain where carbons are connected by single bonds
ü tetrahedral geometry/sp3 hybridized
ü least reactive hydrocarbon family
ü can be in a continuous chain or in rings
ü can have substituent groups(other atoms) attached to the chain
ü To name straight chained alkanes: prefix stem representing the # of carbons in the chain & the suffix “ane” ending
Examples: Name these alkanes
CH4 CH3CH2CH3 (C3H8)
ü To name branched alkanes: identify & name the longest carbon chain. This is called the parent chain which is named using a root to indicate the # of carbons followed by “ane”.
ü Number the chain so branching occurs at the smallest numbered carbon (this number will designate the location of the substituent group).: The positions of substituent groups are specified by numbering the longest chain of carbon atoms sequentially starting at the end closest to the substituent group.
ü Identify & name the substituent groups: Substituent groups are named using a root to indicate the # of carbons in the group followed by “yl”. The prefixes di-, tri-,etc are used to indicate multiple identical substituents. –CH3 is methyl CH2CH3 is ethyl
ü Designate the location of each substituent group by an appropriate number & name. Identify where in the chain the substituent group is located with a number placed before the name. If two are on the same carbon use that number twice. Separate the number and the name with a hyphen and commas to separate numbers from each other.
ü The location & name of the substituent groups are followed by the root alkane name. The substituents are listed in alpha order.
ü The same rules apply for alkenes & alkynes but always count from the end of the chain that the multiple bond is closer to; disregard the branch chain rule used for alkanes.
Example: Name this!
CH3CH(CH3)CH2CH3
Alkenes (CnH2n)
ü unsaturated hydrocarbon chain where carbons are connected by at least 1 double bonds
ü trigonal planar geometry/sp2 hybridized
ü To name alkenes: Indicate where the double bond is by numbering the longest chain that contains the double bond starting with the one closest to the bond. Then use the prefix stem to indicate the number of carbon atoms in the chain & the suffix “ene” ending.
Examples: Name these alkenes
C3H6
Alkynes (CnH2n-2)
ü unsaturated hydrocarbon chain where carbons are connected by at least 1 triple bonds
ü linear geometry/sp hybridized
ü To name alkynes: Indicate where the triple bond is by numbering the longest chain that contains the triple bond starting with the one closest to the bond. Then use the prefix stem to indicate the number of carbon atoms in the chain & the suffix “ene” ending.
Examples: Name these alkenes
C2H2