1(g) covalent bonding

Question 1

why does covalent bonding occurs?

Answer 1

so that non-metals atoms can share electrons with other non-metal atoms to obtains a full outer shell of electrons

Question 2

strength of covalent bonds?

Answer 2

very strong

Question 3

how is a molecule formed with covalent bonding?

Answer 3

when two or more atoms bond togehter

Question 4

intermolecular forces?

Answer 4

the weak attractive forces which act between molecules (much weaker than covalnet bonds)

Question 5

electrostatic attraction ?

Answer 5

There is a strong electrostatic attraction between the shared pair of electrons and the nuclei of the atoms involved, since the electrons are negatively charged and the nuclei are positively charged

Question 6

simple molecular structures?

Answer 6

Simple molecules contain only a few atoms held together by covalent bonds.
They have a low melting point as there are only weak intermolecular forces acting between the molecules

Question 7

what happens as the molecule increases in size in a simple molecular structure?

Answer 7

the intermolecular forces also increase as there are more electrons available

Question 8

why does melting point increases will relative moleuclar mass of a substance increasing?

Answer 8

An increase in the relative molecular mass of a substance means that there are more electrons in the structure, so there are more intermolecular forces of attraction that need to be overcome when a substance changes state (a larger amount of heat energy is needed to overcome these forces)

Question 9

giant covalent structure?

Answer 9

have a huge number of non-metal atoms bonded to other non-metal atoms via strong covalent bonds (giant lattices)

Question 10

what are the 3 giant lattices we need to know?

Answer 10

• diamond
• graphite
• C60

Question 11

How are diamond and graphite different?

Answer 11

• they both contain only carbon atoms but due to the differences in bonding arrangements they are physically completely different

Question 12

organisation of diamond?

Answer 12

each carbon atoms bonds with four carbon atoms forming a tetrahedron

Question 13

physical properties of diamond?

Answer 13

• It does not conduct electricity
• It has a very high melting point
• It is extremely hard and has a density of 3.51 g / cm3 – a little higher than that of aluminium

Question 14

silicon dioxide properties?

Answer 14

a giant covalent compound which is structurally similar to diamond. Each Oxygen atom forms covalent bonds with 2 silicon atoms and each silicon atom in turn forms covalent bonds with 4 oxygen atoms
(tetrahedron is formed with one silicon atom and four oxygen atoms, similar to diamond)

Question 15

structure of graphite?

Answer 15

• each carbon atom in graphite is bonded to three other forming layers of hexagons - this leaves one free electron per carbon atom

Question 16

why can graphite conduct electricity?

Answer 16

These free electrons migrate along the layers and are free to move and carry charge, hence graphite can conduct electricity

Question 17

why is graphite soft and slippery?

Answer 17

the covalent bonds within the layers are very strong, but the layers are attracted to each other by weak intermolecular so the layers can slide over ach other making graphite soft and slippery

Question 18

physical properties of graphite?

Answer 18

• it conducts electricity and heat
• it has a very high melting point
• it is soft and slippery and less dense than diamond

Question 19

composition of C60 fullerene?

Answer 19

• a group of carbon allotropes which consist of molecules that form follow tubes or spheres
• 60 carbon atoms are joined together forming 20 hexagons and 12 pentagons which produce a hollow sphere shape