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The joining of two atoms in a stable arrangement
Elements gain, lose, or share electrons to reach the electron configuration of the noble gas closest to them in the periodic table
Two types of bonding◦ Ionic bonds: result from the transfer of electrons
from one element to another◦ Covalent bonds: result from the sharing of
electrons between two atoms
Bonding
A pure substance that cannot be broken down into simpler substances by a chemical reaction
Identified by a one- or two-letter symbol Arranged in the periodic table Its location on the periodic table indicates a
lot about its chemical properties Can be a metal, nonmetal, or a metalloid
Elements
Ionic bonds Ionic bonds
◦ Form between a metal (left side of periodic table) and a nonmetal (right side of periodic table
Covalent bonds◦ Form when two nonmetals combine ◦ Form when a metalloid bonds to a nonmetal
Periodic Table
A main group element is especially stable when it possesses an octet of e- in its outer shell
Octet rule
octet = 8 valence e−
Charge based on periodic group
group 1A:
group 2A:
group 3A:
M1 valence e−
M+ + e−
M2 valence e−
M2+ + 2e−
M3 valence e−
M3+ + 3e−
the cation charge = the group number
Charge based on periodic group
group 6A: X6 valence e−
+ 2e− X 2−
group 7A: X7 valence e−
+ e− X −
the anion charge = 8 – group number
charge = 8 – 6 = 2
charge = 8 – 7 = 1
The sum of the charges in an ionic compound must be zero overall
Ions will arrange to maximize anion-cation attractions and minimize anion-anion and cation-cation repulsions
Ionic compounds
There must be two F- anions for each Ca+ cation to have an overall charge of zero
Ion compounds – charge balance
Formula for ionic compounds
HOW TO Write a Formula for an Ionic Compound
Step [1]
Identify which element is the cationand which is the anion.
Step [2]
Determine how many of each ion type is needed for an overall charge of zero. When the cation and anion have different
charges, use the ion charges to determine the number of ions of each needed.
Step [3]
To write the formula, place the cationfirst and then the anion, and omit charges.
Calcium Iodide◦ Cation = calcium
Charge 2+◦ Anion = iodine
Charge -◦ Need two iodine for every calcium for an overall
charge of zero◦ CaI2
Example
Ionic comound criss-cross rule
“Criss-cross” rule Make magnitude of charge on one ion into
subscript for other When doing this, make sure that subscripts are
reduced to lowest whole number.
Al2O3Al3+ O2–
Main group cations
Main group cations are named for the element from which they are formed.
Na+ K+ Ca2+ Mg2+
sodium potassium calcium magnesium
Systematic name◦ Follow the name of the cation by a Roman
numeral in parentheses to indicate its charge
Common name◦ Use suffic “-ous” for the cation with a smaller
charge and suffix “-ic” for the cation with a higher charge
Multiple charge cations
Fe2+
iron(II)Fe3+
iron(III)
ferrous ferricFe2+ Fe3+
Name the cation and then the anion Do not specify the charge on the ion Do not specify how many ions of each type
are needed to balance charge
Naming ionic compounds
Na+
sodiumF−
fluorideNaF
sodium fluoride+
Mg2+
magnesiumCl−
chlorideMgCl2
magnesium chloride+
Naming ionc compoundsHOW TO Name an Ionic
CompoundStep [1] Determine the charge on the cation.
Step [2] Name the cation and the anion
If the cation could be multiple charges indicate the charge with roman numerals or with a –ous / -ic suffix.
Step [3]
Write the name of the cation first then the name of the anion
K2O◦ Cation = K+
◦ Anion = O2-
◦ Potassium Oxide LiBr
◦ Cation = Li+
◦ Anion = Br-
◦ Lithium Bromide SnO
◦ Cation = Sn2+
◦ Anion = O2-
◦ Tin (II) Oxide /Stannous Oxide
Examples
Naming ionic compoundsHOW TO Derive the Formula from the Name of
an Ionic Compound
Step [1] Identify the cation and the anion.
Step [2] Determine the charge on the cation and anion.
Step [3]
Balance the charges.
Step [4]
Write the formula with the cation first and use subscripts to communicate charge balance.
Cobalt (II) Oxide/Cobaltous Oxide◦ Cation = Co 2+
◦ Anion = O2-
◦ CoO Iron(III) Fluoride/Ferric Flouride
◦ Cation = Fe3+
◦ Anion = F-
◦ FeF3
Beryllium Chloride◦ Cation = Be2+
◦ Anion = Cl-
◦ BeCl2
Examples
Ionic compounds are crystalline solids with very high melting and boiling points
When ionic compounds dissolve in water, they separate into cations and anions, increasing the conductivity of the solution
Physical properties of ionic compounds
NaCl
+
water solution
A cation or anion that contains more than one atom
The multiple atoms are held together with covalent bonds
The molecule has an overall charge associated with it
Polyatomic ions
When a cation and anion of equal charge combine, only one of each ion is needed
Formulas for polyatomic ions
Na+ NO2−+ NaNO2
zero overallcharge
Ba2+ SO42−+ BaSO4
zero overallcharge
When a cation and anion of unequal charge combine, use the ionic charges to determine the relative number of each ion that is needed
Formulas for polyatomic ions
Mg2+ OH−+ Mg(OH)2
zero overallcharge
+2 charge means2 OH− anions are
needed.
−1 charge means1 Mg2+ anion is
needed.
The same rules are followed for naming standard ionic compounds:
• Name the cation and then the anion.• Do not specify the charge on the ions.• Do not specify how many ions of each type
are needed to balance charge.•Use –ite suffix if 1 or less Oxygen atoms in anion•Use –ate suffix if more Oxygen atoms in anion•Use bi- prefix or write hydrogen if H part of anion
Naming polyatomic ionic compounds
NaHCO3 Al2(SO4)3
sodium bicarbonate aluminum sulfate