1. Bond Types & Properties

2. Why bond?  Atoms form chemical bonds to reach an octet (s 2 p 6 ) in the valence shell  This creates a more stable molecule and releases energy  The converse must also be true If energy is released in forming bonds, it will take energy to break a chemical bond

3. Ionic Bonds  Made by the attraction of positive and negative ions  Total charge will be neutral  High melting & boiling points  Frequently very hard but also brittle  Frequently soluble in water  Conduct electricity in water solution (electrolyte)  Conduct electricity as when melted

4. Covalent Bonds  Covalent Bonds share electrons instead of transfer them permanently from one atom to another as ions do  Electrons are shared as pairs – one from each atom  The distance between two bonded atoms is the bond length

5. Formation of a Covalent Bond  The positive nucleus of each atom is attracted to negative electron cloud of the other atom + - + -

6.  The positive nucleus of each atom is repelled by positive nucleus other atom  Each electron cloud also repels + - + -

7. Bond Length  The balancing of the attraction and repulsion between the atoms balances out to the minimum potential energy and the bond length is set + - + -

8. Non-polar Covalent  Share electrons between two atoms “evenly”  Do not conduct electricity (non-electrolyte)  Frequently liquids or have low melting and boiling points  Not soluble in water

9. Polar Covalent  Share electrons between two atoms “unevenly”  Moderate melting & boiling points  Sometimes soluble in water

10. Determining Polarity  The electronegativity of atoms determines if a bond will be ionic, polar covalent, or non-polar covalent  If the differences in electronegativities is above 1.6, it is considered an ionic molecule  If the differences in electronegativities is above.4, it is polar covalent  If the differences in electronegavities is.4 or below, it is non-polar covalent

11. Metallic  Sharing of electrons throughout the whole piece of metal – a sea of electrons  Not soluble in water  Conduct electricity as a solid  Malleable – can be hammered into a sheet  Ductile – can be pulled/extruded into a wire  Typically high melting & boiling points

12. Summary MeltingSolubility in water Conductivity IonicHighYesIn water solution Polar CovalentMediumSometimesUsually Non-Polar Covalent LowNo MetallicHighNoAs a solid