Types of Chemical Bonds (Chapter 4)

Ionic Bonds (pages 114-119)
Ionic bonds are formed by the transfer of electrons between atoms (between a metal and nonmental).

Ions are produced during ionic bonding.

Ions are charged particles formed by losing or gaining electrons. A superscript is a small number written to the right and above the symbol for an element that tells the charge on the ion. "1"is not written. A "1+" or "1-" superscript is written "+" or "-".

Positive Ions (metals)
Examples (metals)
Li+
Al3+
Mg2+
K+
Positive ions are metals that lose electron(s).

Negative Ions
Examples
Cl-
O2-
N3-
C4+
Negative ions are nonmetals and polyatomic ions that gain electron(s).

Polyatomic Ions - atoms that act together like one atom to form chemical bonds
Examples of polyatomic ions
bicarbonate HCO3 1-
sulfate SO4 2-
carbonate CO3 2-
phosphate PO4 3-
Ammonium NH4+

Ionic Compounds
Examples
NaCl Salt
MgO Magnesium oxide
KI Potassium iodide
AlPO4 Aluminum phosphate

Naming Ionic Compounds

Binary Compounds - formed from two elements and/or polyatomic ions ("bi" means two)
1. Always name the metal (positive ion) first.
2. Then drop the ending of the nonmetal and add "ide"
3. Polyatomic names do not change.

Examples
sodium chloride, aluminum bromide, potassium iodide, magnesium oxide
calcium carbonate, magnesium sulfate, potassium phosphate, ammonium nitrate

Writing the formulas for compounds using the cris-cross method

First determine the charge on the ions and write the charges as superscripts (to the right and above the formula).

Then write the metal (+ Charge ) first.

Now ignore the positve and negative signs and criss-cross the charge on the ions to form the subscripts in the formulas.

If the subscripts are the same they cancel one another out and there will be only one of each ion.

Polyatomic ions act together like one ion.

Examples
Ca2+ + Cl- produces CaCl2

Mg2+ + O2- produces MgO

K+ + PO43- produces K3PO4

Properties of Ionic Compounds
Crystal structure of atoms
Example Halite (salt) (cubic crystal)

High melting points
NaCl - 801 degrees C

Conduct electricity when in solution with water. Electricity is the flow of electric charge. Ionic compounds usually do not conduct electricity in their solid form. They must be in solution.

Covalent Bonds