Bonding Lab
Bonding
Discussion
Bonding
Ionic
Covalent
Metallic
Determined by difference in
Electronegativity between atoms.
• Ionic Compounds
• Covalent Compounds
• Crystalline solids (made of
ions)
• High melting and boiling
points
• Conduct electricity when
melted or dissolved.
• Many soluble in water but
not in nonpolar liquid
• Gases, liquids, or solids
(made of molecules)
• Low melting and boiling
points
• Poor electrical conductors in
all phases
• Many soluble in nonpolar
liquids but not in water
• Ionic Compounds
• Covalent Compounds
• Structure and Function
• Structure and Function
Most covalent compounds have relatively low melting points and boiling points.
While the ions in an ionic compound are strongly attracted to each other, covalent bonds create molecules that can separate from
each other when a lower amount of energy is added to them. Therefore, molecular compounds usually have low melting
and boiling points.
Covalent compounds usually have lower enthalpies of fusion and vaporization than ionic compounds.
The enthalpy of fusion is the amount of energy needed, at constant pressure, to melt one mole of a solid substance. The enthalpy
of vaporization is the amount of energy, at constant pressure, required to vaporize one mole of a liquid. On average, it takes only
1% to 10% as much heat to change the phase of a molecular compound as it does for an ionic compound.
Covalent compounds tend to be soft and relatively flexible.
This is largely because covalent bonds are relatively flexible and easy to break. The covalent bonds in molecular compounds cause
these compounds to take form as gases, liquids and soft solids. As with many properties, there are exceptions, primarily when
molecular compounds assume crystalline forms.
Covalent compounds tend to be more flammable than ionic compounds.
Many flammable substances contain hydrogen and carbon atoms which can undergo combustion, a reaction that releases energy
when the compound reacts with oxygen to produce carbon dioxide and water. Carbon and hydrogen have comparable
electronegativies so they are found together in many molecular compounds.
When dissolved in water, covalent compounds don't conduct electricity.
Ions are needed to conduct electricity in an aqueous solution. Molecular compounds dissolve into molecules rather than
dissociate into ions, so they typically do not conduct electricity very well when dissolved in water.
Many covalent compounds don't dissolve well in water.
There are many exceptions to this rule, just as there are many salts (ionic compounds) that don't dissolve well in water. However,
many covalent compounds are polar molecules that do dissolve well in a polar solvent, such as water. Examples of molecular
compounds that dissolve well in water are sugar and ethanol. Examples of molecular compounds that don't dissolve well in water
are oil and polymerized plastic.
Note that network solids are compounds containing covalent bonds that violate some of these "rules". Diamond, for example,
consists of carbon atoms held together by covalent bonds in a crystalline structure.
Ionic vs. Covalent
• Ionic – Chlorine takes
the electron from
sodium.
• Covalent – Two
oxygen atoms share
the electrons equally.
Ionic Bonding
One metal and one non-metal.
Positive and negative IONS
Attraction between positive and negative.
Positive and negative IONS
Becomes brittle when the like charges line up and repel.
Ionic
Ionic
Nonpolar Covalent Bonding
Two non-metals.
Covalent
Metallic Bonding
Metallic Crystal
Shells overlap.
Malleable
Ductile
Heat Conductor
Electrical Conductor
Video
• Video – Metallic bonding and metallic properties
Polar Covalent
Bonding
Polarity
strength of 2 students tugging on a
rope. Tug of war with equal
(covalent) strength, with offset
(weak and strong polar) strength
and if one completely takes the
rope (ionic).
Polar Covalent
• Oxygen has higher
electronegativity than
Hydrogen.
• The electrons spend
more time closer to the
Oxygen atom.
Summary
Ionic - Transfer
Covalent Equal sharing
Polar Covalent Unequal sharing
Polar molecules from
summation of polar bonds.
Polar Molecules vs Polar Bonds