Principles Of Chemistry - Covalent Bonding Flashcards
When does covalent bonding occur?
Covalent bonding occurs in most non - metallic elements and in compounds of non metals
When atoms share pairs of electrons, they form covalent bonds. The bonds between these atoms are strong.
Explain covalent bonding in terms of electrostatic attractions
Strong bonds between atoms that are covalently bonded are a result of electrostatic attraction between the positive nuclei of the atoms and the pairs of negative electrons that are shared between them
Why do substances with simple molecular structures have low melting and boiling points?
Substances that consist of small molecules are usually gases or liquids with low melting/ boiling points. They have weak intermolecular forces between the molecules, which are what are broken when boiling. These substances also don’t conduct electricity because they don’t have an overall charge
Why do the melting and boiling points of structures with simple molecular structures increase, in general, with increasing relative molecular mass?
The intermolecular forces increase with the size of the molecules, so larger molecules (ie molecules with larger relative atomic masses) have higher melting and boiling points
Why are substances with giant covalent structures solids with high melting and boiling points?
All of the atoms in these structures are linked to other atoms by strong covalent bonds. These bonds must be overcome to melt or boil these substances
How does the structure of diamond influence it’s physical properties?
In diamond, each carbon is joined to 4 carbons covalently. It’s very hard with a very high melting point and does not conduct electricity
How does the structure of graphite influence it’s physical properties?
In graphite, each carbon atom is covalently bonded to 3 other carbons, forming layers of hexagonal rings, which have no covalent bonds between the layers. The layers can slide over each other due to no covalent bonds between the layers, but weak intermolecular forces. Meaning that graphite is soft and slippery.
One electron from each carbon atom is delocalised. This makes graphite similar to metals, because of it’s delocalised electrons. It can conduct electricity, unlike diamond.
How does the structure of graphene influence it’s physical properties?
This is a single layer of graphite which has properties with makes it useful in electronics and composites.
What are fullerenes?
Molecules of carbon atoms with hollow shapes. They are based on hexagonal rings of carbon atoms, but also may contain rings with five or seven carbon atoms. First one to be found was buckminsterfullerene (C60), which has a spherical shape.
How does the structure of carbon nanotubes influence it’s physical properties?
They are cylindrical fullerenes with very high length to diameter ratios. Their properties make them useful for nanotechnology, electronics and materials
