Covalent and Metallic Bonds

Covalent bonds Recall that ionic bonds are when electrons are transferred (give and take) between atoms Covalent bonds are formed when atoms SHARE electrons. Carbon has four valence electrons, which does not make it ideal to become an ion (give or lose it’s electrons) because it takes too much energy. So instead it shares!

Covalent compounds Elements on the periodic table that are close together are more likely to share electrons to form covalent bonds Covalent compounds are especially important in living organisms DNA Proteins Sugars Organic compounds – containing carbon atoms

Properties of Covalent Compounds Can be solids, liquids or gases at room temperature Lower melting and boiling points than ionic compounds Do not separate in water, nor does their solution conduct electricity

Bonds Single bond – one shared pair of electrons Double bond – two shared pairs of electron Stronger than single bonds Triple bond- three shared pairs of electrons Stronger than double and single bonds Acetylene (gas used by welders) is an example Nitrogen molecule (N2)

Metallic Bonds Metallic bond is a bond formed when many metal atoms share their pooled electrons Can bond to the same metal atoms or different ones Electrons are not transferred, they move freely throughout the piece of metal Electrons are not attracted to any particular atom Properties: good conductors of heat and electricity Malleable Ductile

Forming solids - crystals A crystal is a regular, repeating arrangement of atoms, ions or molecules Visualizing pg234

Forming solids - polymers Polymers is a covalent compound made up of many small, repeating units linked together in a chain. EXAMPLES: plastics, synthetic fibers, many paints, synthetic elastic compounds