1g - covalent bonding Flashcards
what is the difference between covalent bonds and ionic bonds?
covalent: electrons are shared between atoms
ionic: electrons are transferred from one atom to another
what is represented by a short straight line between two atoms?
a covalent bond
true or false?
simple covalent molecules conduct electricity.
false.
they do not conduct electricity as they do not contain free electrons
what is a covalent bond?
it is a type of chemical bond where atoms share pairs of electrons with each other
what are intermolecular forces
the weak forces of attraction that exist between individual molecules in a covalent substance.
true or false?
covalent bonds involve the transfer of electrons.
false.
they share instead of transfer electrons
what type of materials form a covalent bond?
non-metals
what makes each atom more stable in a covalent bond?
it allows each atom to achieve an electron configuration similar to a noble gas
what is formed when a group of two or more atoms covalent bond together?
a compound / molecule
true or false?
dot and cross diagrams can represent giant covalent structures
false.
dot and cross diagrams are used to represent only small covalent molecules with a fixed number of atoms
what are simple molecular?
a small covalent molecule with a fixed number of atoms
what are diatomic molecules?
they are molecules composed of two atoms.
what are inorganic molecules?
simple molecules that do not contain carbon atoms
what is an organic molecule?
a simple molecule that contains carbon and hydrogen atoms
true or false?
simple molecular structures have high melting and boiling points
false they have low bp and mp
true or false?
covalent compounds are good conductors of electricity
false.
they are poor conductors of electricity
what are simple molecular structures?
small molecules with covalent bonds, which have weak forces between the molecules
why are covalent compounds generally poor conductors of electricity?
they do not contain free ions or electrons to carry the charge
true or false?
covalent bonds break when a covalent substance melts or boils.
false
INTERMOLECULAR FORCES break when a covalent substance melts or boils
what happens to melting and boiling as the relative molecular mass of a substance increases
they increase due to the increased number of electrons and stronger intermolecular forces.
what are insulators?
materials that do not allow the flow of electric charge or heat, and common insulators include plastics, rubber and wood
why do simple molecular structures have low melting and boiling points?
this is due to weak intermolecular forces which require small amounts of energy to overcome.
true or false?
simple molecular structures are often gases or liquids at room temperature.
true.
what are giant covalent structures?
they are macromolecules or giant lattices that consists of a huge number of non-metal atoms with strong covalent bonds fixed in a ratio.
define allotropes.
they are different structural forms of the same element, such as diamond and graphite for carbon.
why does diamond not conduct electricity?
all the outer shell electrons are held in the covalent bonds, and there are no freely moving charged particles to carry the current.
what are fullerenes?
a group of carbon allotropes that consist of molecules forming hollow tubes or spheres.
describe the structure of graphite.
- each carbon atom is bonded to three others
- there are hexagonal layers
- there is one free/delocalised electron per carbon atom
state the properties of diamond.
it doesn’t conduct electricity, has a high melting point and is extremely hard.
what are the properties of graphite?
it conducts electricity and heat, has a high melting point, and is soft and slippery
true or false?
fullerenes have a high surface area
true
describe the buckminsterfullerene
a carbon allotrope with 60 carbon atoms forming a hollow sphere. each carbon atom is bonded to three others and there is 1 free/delocalised electron per carbon atom
why are c60 fullerene and graphite good electrical conductors?
because they have delocalised electrons to carry the current.
