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The valence electrons in an atom have HIGH POTENTIAL ENERGY
By bonding with other atoms, potential energy is decreased creating
stable compounds.
Symbols of atoms with dots to represent the valence-shell
electrons. (The valence- are the e- directly involved in
bonding).
Ar Mg
C
The Noble Gases do not react with other elements because they are already
STABLE.The outer most “s” and “p” orbitals are completely filled with 8
electrons, satisfying the octet rule.
Ne
Elements combine with each other to achieve noble gas electron configurations
or(8 outer e-)
**The exceptions to the octet rule are Hydrogen and Helium
(they only need 2)
• The forming of chemical compounds results in chemical change.
• Compounds are made up of chemically united elements
• Compounds have completely different characteristics than its
component elements• Compounds are NEUTRAL
2H2O = H2O = HHO H2O HHO
Subscript = # of atomsCoefficient = # of molecules
N: 1H: 5O: 1
The Gaining and Losing of Electrons
to form IONS. (An ion is an atom with a charge.)
sharing of electrons
• Soluble in water• Do not transmit electric current• Brittle • High melting and boiling points
Ionization Energy: the amount of energy needed to remove an e- from
an atom. Nonmetals have
high ionization
energy because they are closer to satisfying the octet
rule!
Metals have a
low ionization
energy
the higher the electronegativity the greater the ability to pull electron to itself
The nature of a bond is determined by differences in electronegativity. The GREATER the electronegativity difference, the MORE ionic the bonding.
Ionic compounds result when metals react with nonmetals
• Metals lose electrons to achieve a stable outer energy level
• Positive ions form when electrons are given away
Group 1 metals ion 1+
Group 2 metals ion 2+
Group 13 metals ion 3+
1. Write the symbol for the cation (+) followed by the symbol for the anion (-).
2. Put any polyatomic ions (see green boxes) in parenthesis
3. Write the oxidation numbers above the appropriate ions
4. Use the criss-cross method to deterimine # of atoms (do not criss-cross ones)
5. Make sure the sum of all ox# is ZERO.6. Reduce
Na – e Na +
Sodium Atom
Sodium Ion
11 p+11 e-
0
11 p+10 e-
1+
+ e 1-
Fluoride Atom
Fluoride Ion
17 p+17 e-
0
17 p+18e-
1-
Na + Na1+ 1-
YOUR TURN…
Using dot diagrams, draw the Lewis structures that result when the following elements form ionic bonds:
A. Potassium + chlorine
B. Magnesium + fluorine
Potassium + Chlorine
Magnesium + Fluorine
K Cl K Cl+
FMg + F FMg
Oxidation: the process of losing electrons
▪ Creates an ion with a + charge▪ Creates cations
Reduction: the process of gaining electrons
▪ Creates an ion with a – charge▪ Creates anions
1. Write the name of the cation (+)2. Write the name of the anion (-) with an
ide suffix
NaClSodium and Chlorine
Sodium Chloride
The oxidation number is not always the same, it varies.
The variable oxidation states are represented with a roman numeral in
parentheses and are located in groups 3-12 on the periodic chart.
Copper Copper (I) = Cu+ Copper (II) = Cu2+
Write the symbol for the cation followed by the symbol for the anion.
Write the oxidation numbers above the appropriate ions.
Criss-CrossCopper(III) Oxide: CuO Cu2O3
Copper(I) Oxide: CuO Cu2O
3+ 2-
1+ 2-
SO4 Sulfate 2-C2H302Acetate 1-NO3 Nitrate 1-NO2 Nitrite 1-NH4 Ammonium 1+HCO3 Bicarbonate 1-CO3 Carbonate 2-OH Hydroxide1-ClO3 Chlorate 1-PO4 Phosphate 3-
1. Write the name of the cation (+)2. Write the name of the anion (-)3. If either is a polyatomic ion write the
name of the polyatomic ion (you don’t need to change any suffixes)
Na(OH)Sodium Hydroxide
Write the symbol for the cation followed by the symbol for the anion.
Put all polyatomic ions in parentheses!! Write the oxidation numbers above the
appropriate ions. Criss-CrossCalcium Phosphate: Ca(PO4) Ca3(PO4)2
Ammonium Phosphate: (NH4)(PO4) (NH4)3(PO4)
2+ 3 -
1+ 3 -
Cu(OH) Copper (I) Hydroxide
Ni2O3 Nickel (III) Oxide
1- = 01+
2-6- =03+
sharing of electrons
Between nonmetallic elements of similar electronegativity.
Formed by sharing electron pairsStable non-ionizing particles, they
are not conductors at any stateExamples; O2, CO2, C2H6, H2O, SiC
Water is a polar molecule because oxygen is more electronegative than hydrogen, and therefore electrons are pulled closer to oxygen.
A polar molecule has a (+) and a (-) end.
A nonpolar molecule does not have charged ends.
Metal + Nonmetal --> ionic compound (usually)
Metal + Polyatomic ion —> ionic compound (usually)
Nonmetal + Nonmetal —> covalent compound (usually)
Hydrogen + Nonmetal —> covalent compound (usually)
The chemical symbol for the atom is surrounded by a number of dots corresponding to the number of valence electrons
1. Write the name of the cation (+) with appropriate prefix (do NOT use mono for the cation)
2. Write the name of the anion (-) with the appropriate prefix
CO2
Carbon Dioxide
1: mono2: di3: tri4: tetra5: penta6: hexa
Formula weight is the sum of the atomic masses.
Example- CO2Mass, C + O + O
12.011 + 15.994 + 15.99443.999