Chemical Bonding

1. Chemical Bonding

2. Chemical Bonds The attractive force that holds atoms together Bonding is responsible for the chemical and physical properties of many substances Only valence electrons are involved in bonding

3. Types of Bonding Ionic Bonding Covalent Bonding

4. Ionic bonding Bonding which involves transfer of electrons Normally involves bonding between a metal and a nonmetal Examples: NaCl, KBr, MgCl2, Mg3N2,etc.

5. Covalent bonding Bonding which involves sharing of electrons Normally occurs in molecules and molecular compounds Covalent bonds can be represented either by a pairs of dots or dashes Examples: H2, Cl2, O2, N2, etc.

6. Electronegativity This is a measure of the tendency of an atom to attract shared electrons to itself Atoms of the most electronegative elements have the greatest attraction for electrons Fluorine has the highest electronegativity value (4.0 on the Pauling scale) Francium has the lowest electronegativity value

7. Polar covalent bond Bonding in which electrons are shared unequally between atoms This is due to differences in electronegativity values between atoms

8. Characteristics of Ionic Compounds Hard and brittle Conduct the electric current when either molten or dissolved in water (not when solid) Have high melting and boiling points Solid at room temperature Exist as positive and negative ions

9. Characteristics of Molecular compounds Tend to be solid, liquid or gas at room temperature Exists as molecules Usually have lower melting/boiling points than ionic compounds Poor conductors of electricity