1. Chemical Bonds

2. Compound: a substance made from chemical bonding atoms of two or more elements.
Chemical bond: a force that holds together the atoms in a substance.
Remember: Atoms form compounds to become chemically stable. An atom is chemically stable when the outer level is complete or full (8 valence electrons.)

3. Chemical Formula: tells what elements a compound contains and the number of those atoms.
How to Count Atoms:
Coefficient: the number of molecules Superscript: represents
the oxidation
number of how many
electrons lost or gained.
2 H2O SO42-
Subscript: the # of atoms of an element in each molecule

4. Two Types of Chemical Bonds:
Ionic Bonds
transferring electrons between atoms of a metal and nonmetal
Covalent Bonds
sharing electrons between atoms of a nonmetal and nonmetal

5. Ionic Bond
Definition of Ionic Bond: The attraction between 2 oppositely charged ions (+ and -)
Ion: an atom or group of atoms that have become electrically charged.
Positive Ion: when an atoms loses an electrons it loses a negative charge protons > electrons
Negative Ion: when atom gains an electron it gains a negative charge
electrons > protons

6. 11 Protons
12 Neutrons
10 Electrons
11 Protons
12 Neutrons
11 Electrons

7. Note:
Atoms that have fewer than 4 Valence electrons, want to get rid of them…transfer electrons to other atoms.
Atoms that have more than 4 Valence electrons, want to gain more electrons.

9. Example of Forming an Ionic Bond:
Na = 1 valence electron Cl = 7 valence electrons
Na (sodium) gives Cl (chlorine) one electron
Na now has more protons than electrons → becomes a positive ion.
Cl now has more electrons than protons → becomes a negative ion.
Negative and positive electric charges attract each other
Na Cl 1- → Na+Cl-

11. Oxidation Number: the overall charge on the atom after losing or gaining an electron(s)
Group #
Elements
Oxidation #
Group 1
Li, Na, K 1+
Group 2
Mg, Be, Ca 2+
Group 16
O, S 2-
Group 17
F, Cl,Br, I 1-

12. Naming Ionic Compounds
The name of the positive ion comes first.
The name of the negative ion comes next
If the negative ion is an element, the end of its name changed to –ide.
Example: MgO = Magnesium oxide.

13. Properties of Ionic Compounds
Crystal shape
High Melting Points
Electrical Conductivity
When ionic compounds dissolve in water, the solution can conduct electricity.
Example: salt in water.
Solid ionic compounds do not conduct electricity well