4.1 - Covalent Bonding

Question 1

covalent bond

Answer 1

electrostatic attraction between the nuclei of bonded atoms and a shared pair of electrons

Question 2

covalent bond is formed

Answer 2

formed between atoms by the sharing of a pair of electrons

Question 3

electrostatic attraction

Answer 3

The attraction between the shared pair of electrons and the nuclei of the atoms involved in a covalent bond

Question 4

covalently bonded substances may be

Answer 4

simple molecular structures or giant covalent structures
- Simple molecular structures –> oxygen and water
- Giant covalent structures –> diamond and graphite

Question 5

simple molecular structures have low melting and boiling points because

Answer 5

There are weak intermolecular forces between the molecules
These forces require little energy to overcome

Question 6

C60 is a simple molecular structure that

Answer 6

can not conduct electricity

Question 7

as the relative molecular mass of a substance increases

Answer 7

the melting and boiling point will increase as well
-> more electrons in the structure, so there are more intermolecular forces of attraction that need to be overcome
-> larger amounts of heat energy are needed to overcome these forces, causing the compound to have a higher melting and boiling point

Question 8

simple molecular structures are poor conductors of electricity (even when molten) because

Answer 8

• no free ions or electrons to move and carry the charge -> neutral charge
• most covalent compounds do not conduct at all in the solid state
• insulators

Question 9

giant covalent structures

Answer 9

solids with high melting points, giant lattices

Question 10

examples of giant covalent structures

Answer 10

diamond and graphite

Question 11

all giant covalent structures have high melting points because

Answer 11

• strong covalent bonds between atoms
• these require lots of energy to overcome

Question 12

properties of diamond and use

Answer 12

diamond is very hard:
- each carbon atom is covalently bonded to four other carbon atoms
- the covalent bonds are very strong
- tetrahedron shape (each atom bonded to four carbon atoms)
the hardness of diamond makes it useful for cutting tools

Question 13

Diamond has a high melting point because

Answer 13

a giant covalent structure
- there are strong covalent bonds between atoms which need lots of energy to break

Question 14

properties of graphite and use

Answer 14

• soft and slippery
• each carbon atom is bonded to three other carbon atom forming layers
• layers are free to slide over each other because there are only weak forces between the layers, not covalent bonds
• graphite is used as pencil lead

Question 15

graphite can conduct electricity and heat because

Answer 15

delocalised electrons are free to move

Question 16

graphite has a high melting point because

Answer 16

• giant covalent structure
• strong covalent bonds between atoms which need lots of energy to break

Question 17

covalent compounds do not usually

Answer 17

conduct electricity

Question 18

molecule

Answer 18

group of atoms joined by covalent bonds

Question 19

why does lithium fluoride form ionic bonds

Answer 19

lithium gives one electron to fluoride (metal -> non-metal)
- flouride gains one electron and hydrogen looses one

Question 20

relative mass

Answer 20

(number x percent)+(number x percent) / 100

Question 21

metals structure and bonding

Answer 21

giant metallic
metallic
-> high MP+BP

Question 22

metals with non-metal structure and bonding

Answer 22

giant ionic
ionic
-> high MP+BP

Question 23

group 4 structure and bonding

Answer 23

giant covalent
covalent bonds
-> high MP+BP

Question 24

non-metals structure and bonding

Answer 24

simple molecular
covalent bonds
-> low MP+BP

Question 25

C60 properties

Answer 25

• simple molecular structure
• allotrope of carbon
• 60 carbon atoms

Question 26

C60 properties mentioning structure

Answer 26

• low MP/BP point -> forces between molecules are weak but has large molecules
• so C60 has high MP for a molecular substance
• molecules are neutrals -> not able to conduct electricity -> insulator
• soft and slipper -> weak forces allow molecules to slide over each other -> malleable

Question 27

silicon dioxide has high melting point

Answer 27

• giant structure -> lots of strong covalent bonds
• takes a huge amount of energy to break

Question 28

silicon dioxide does not conduct electricity

Answer 28

• electrons not free to move
• stuck in covalent bonds

Question 29

giant ionic has high melting point because

Answer 29

• strong forces between oppositely charged ions -> strong and takes lots of energy to break

Question 30

giant ionic conducts electricity when

Answer 30

molten -> ions free to move and carry charge
solid - fixed position and doesn’t carry charge

Question 31

giant metallic has high melting point

Answer 31

strong electrostatic attraction between positive metal ions and delocalised electrons

Question 32

giant metallic conducts electricity

Answer 32

delocalised electrons free to move

Question 33

since giant metallic is metallic the ions

Answer 33

are in layers and can easily slide over each other