Covalent Bonding Flashcards
What is covalent bonding?
The particles in a covalent bond or atoms which share pairs of electrons. It occurs in non-metallic elements and compounds of nonmetals.
What are simple covalent molecules?
Simple covalent molecules are usually gases or liquids that have relatively low melting points and boiling points. This is because there are weak intermolecular forces between molecules, which are easily overcome when a substance melts or boils.
Do simple covalent molecules conduct electricity and why?
These substances are poor conductors of electricity. Simple molecules have no overall charge so they cannot carry electrical charge. Therefore substance made of simple molecules do not conduct electricity.
What are the 4 different types of diagrams that can represent covalent bonds and what are their advantages and disadvantages?
. Dot and cross diagrams with outer shell as circles and dot and cross diagrams with the outer shells electrons show which atom the electrons in bonds come from, but all electrons are identical
. 2D with bonds shows the bond incorrectly at 90° but shows which atoms are bonded together
. 3D ball and stick model attempts to show the correct bond angle is 107.8° and shows the impact of the lone pair
What kind of structures are covalent compounds and why?
Covalent compounds have giant structures which are solid with very high melting points. All the atoms in these structures are linked to other atoms by strong covalent bonds. These must be overcome to melt or boil these structures.
Describe diamond
. Each carbon atom forms four bonds with other carbon atoms
. Diamond is very hard so it is often used to make jewelry and cutting tools
. Diamond has a very high melting point and boiling point so a lot of energy is needed to break the covalent bonds
. Diamond cannot conduct electricity because there are no free electrons or ions to carry a charge
. Diamond is insoluble in water
Describe silicon dioxide
Silicon dioxide (silica) is a giant structure similar to diamond
Describe graphite
. In graphite carbon atom forms three covalent bonds with three other carbons, forming layers of hexagonal rings, which have no covalent bonds between layers.
. Graphite is soft and slippery because layers can easily slide over each other because the weak forces of attraction between layers are easily broken. This is why graphite is used as a lubricant.
. Graphite conducts, electricity, because the free electron from each carbon atoms means that each layer has delocalized electrons which can carry change. It is often use as an electrode for this reason.
Describe graphene
. Graphene is a single layer of graphite
. It is a layer of interlocking, hexagonal rings of carbon atoms, one atom thick
. It is an excellent conductor of thermal energy and electricity
. It’s also has a very low density and is incredibly strong
. It has many uses in the electronics industry
Describe fullerenes
The structure of fullerene is based on hexagonal rings of carbon atoms with hollow shapes. However, they can also have rings of five (pentagonal) or seven (heptagonal) carbon atoms.
Describe cylindrical fullerenes
. Cylindrical fullerenes are called carbon nano tubes
. They are incredibly thin layers
. Their length is much greater than their diameter, giving them high tensile strength and a high electrical and thermal conductivity
Describe cage-like fullerenes
Cage-like fullerenes could also be used for drug delivery into the body. They can also be used as lubricant and catalyst because of the large surface area to volume ratio.
Describe polymers
. Polymers are made up from many small reactive molecules that bond to each other to form long chains
. The atoms in polymer molecules are linked to other atoms by strong covalent bonds
. The intermolecular forces between polymer molecules are relatively strong, and so these substances are solid at room temperature
