Metallic Bond: the attraction of free-floating electrons and neighboring metal
Alloy: 2 or more metals blended together
2 types of alloys:
(1) Substitutional Alloy:
Formed by metals whose atoms are about equal in size
(2) Interstitial Alloy:
(3) Formed when atoms of smaller size fill in spaces between atoms of larger size
Ionic Bonding
Ionic Compound: compound formed between two oppositely charged ions
Ionic Bond: the force of attraction between two oppositely charged ions
Properties of Ionic Compounds:
1. Crystalline Solid
2. High Melting Point
3. Brittle
4. When dissolved in water or in the molten (melted) state, good conductor of
electricity--but not as a solid.
Valence Electrons: electrons found in the outermost energy level of an atom
Octet Rule: Elements gain or lose enough electrons to obtain the electron configuration
of a Noble Gas.
Electron Dot (or Lewis) Structures: the symbol for the element is surrounded by dots
representing valence electrons
Exception-- He:
Charges for ions of Representative Elements:
Group IA: +1
Group IIA: +2
Group IIIA: +3
Group VA: -3
Group VIA: -2
Group VIIA: -1
Naming Ions:
For Cations (Metals): the name of the element is used followed by the word
“ion”.
(e.g., barium vs. barium ion)
For Anions (Nonmetals): the prefix of the element’s name is used with the
addition of the suffix “-ide”. (e.g., chlorine vs. chloride)
Formula unit: one representative particle of an ionic compound.
In all ionic compounds, the positive ion is written first and the negative ion is written
second.
Formula Writing:
Subscript: shows how many atoms of that element are present in a compound
*Note: The subscript “1” is never used in order to avoid confusion. It is understood.
(e.g., NaCl is the formula for sodium chloride. We only need one sodium for every one
chloride.)
Subscripts for ionic compounds should always be reduced to lowest terms.
Naming these compounds:
For the part represented by the positive ion, use the element’s name.
For the part represented by the negative ion, use the anion’s name.
Binary Compounds: compounds formed of two elements
Polyatomic Ions: ions formed from more than one element
Ternary Compound: compounds containing more than two kinds of elements
When more than one polyatomic ion is needed in a formula, use parentheses.
e.g., NH4+ & S-2 = (NH4)2S
Name: ammonium sulfide
When elements have more than one charge, add a Roman numeral in parentheses
behind the element’s name to indicate the charge.
Cu+ = Copper (I)
Cu+2 = Copper (II)
+2
Fe = Iron (II)
Fe+3 = Iron (III)
e.g., Fe+2 & O-2 = FeO = Iron (II) oxide
Fe+3 & O-2 = Fe2O3 = Iron (III) oxide
*Caution!!! Do NOT confuse the Roman numeral with the subscript. It indicates
CHARGE!
Some ionic compounds incorporate water into their crystals.
Hydrate: crystal in which water has been incorporated
The number of water molecules will be shown in the formula.
e.g., CuSO4∙5H2O
Anhydrous: form of the crystal without water
Naming & Writing Formulas for Acids:
Acids are often represented by the general formula, HX.
The name of the acid is determined by the identity of the anion, “X”.
When the anion (X) ends in:
1. –ide: hydro-stem-ic acid
e.g., HCl as a compound would be hydrogen chloride.
As an acid, it would be hydrochloric acid.
2. –ite: stem-ous acid
e.g., H2SO3 as a compound would be hydrogen sulfite.
As an acid, it would be sulfurous acid.
3. –ate: stem-ic acid
e.g., HNO3 as a compound would be hydrogen nitrate.
As an acid, it would be nitric acid.