Covalent bonding

Question 1

What are covalent bonds

Answer 1

When atoms share pairs of electrons, they form covalent bonds.
These bonds between atoms are strong.
Covalently bonded substances may consist of small molecules.

Question 2

What are the types of covalent bonds

Answer 2

Some covalently bonded substances have very large molecules,
such as polymers.
Some covalently bonded substances have giant covalent
structures, such as diamond and silicon dioxide

Question 3

LEARN HOW THESE CAN BE REPERSENTED IN EXAMS( STRUCTURES)

Answer 3

draw dot and cross diagrams for the molecules of hydrogen,
chlorine, oxygen, nitrogen, hydrogen chloride, water,
ammonia and methane

Question 4

What is the limitation of ball and stick

Answer 4

It doesn’t show how the next layer of ions is arranged.
It shows lots of free space between the ions.
It uses sticks to show the forces between the ions( because the forces of attraction between ions actually act in all directions.)

Question 5

Limitations of dot and cross

Answer 5

Fails to illustrate the 3D arrangements of the atoms and electron shells

Doesn’t indicate the relative sizes of the atoms

Question 6

Limitations of 2d / 3d structures

Answer 6

Fail to illustrate the relative sizes of the atoms and bonds. Cannot give you an idea of the shape of a molecule and what it looks like in 3D space.

it is not to scale.

it gives no information about the forces of attraction between the ions, or the movement of electrons to form the ions.

Question 7

Small molecules properties how would you break there bonds

Answer 7

Substances that consist of small molecules are usually gases or
liquids that have relatively low melting points and boiling points.
These substances have only weak forces between the molecules
(intermolecular forces). It is these intermolecular forces that are
overcome, not the covalent bonds, when the substance melts or
boils.

The intermolecular forces increase with the size of the molecules,
so larger molecules have higher melting and boiling points

Question 8

Small molecules properties

Answer 8

These substances do not conduct electricity because the molecules
do not have an overall electric charge.

Question 9

Polymers

Answer 9

Polymers have very large molecules. The atoms in the 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 solids at room temperature

made by linking together large numbers of smaller molecules called monomers

Many everyday materials such as resins, plastics, polystyrene cups, nylon etc. are polymers

Question 10

Giant covalent structures properties and examples

Answer 10

Substances that consist of giant covalent structures are solids with
very high melting 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

Diamond and
graphite (forms of carbon) and silicon dioxide (silica) are examples
of giant covalent structures.