1.g - Covalent Bonding

Question 1

describe the formation of a covalent bond

Answer 1

sharing of a pair of electrons between 2 atoms

Question 2

describe covalent bonding in terms of electrostatic attractions

Answer 2

strong electrostatic attraction between the negatively charged bonding pair of electrons and the positively charged nuclei of the atoms involved in the bond

Question 3

be able to draw covalent dot cross diagrams for diatomic molecules

eg. hydrogen, oxygen, nitrogen, halogens, hydrogen halides

Answer 3

???

look in CGP - pg. 18-19

Question 4

be able to draw covalent dot cross diagrams for inorganic molecules

eg. water, ammonia, carbon dioxide

Answer 4

???

look in CGP - pg. 18-19

Question 5

be able to draw covalent dot cross diagrams for organic molecules containing up to 2 carbon atoms

eg. methane, ethane, ethane , those containing halogen atoms

Answer 5

???

look in CGP - pg. 18-19

Question 6

describe simple molecular substances

Answer 6

weak intermolecular forces of attraction between the molecules = melting + boiling = low

because molecules are easily separated

Question 7

in general why does the melting/boiling point of simple molecular substances increase as the relative molecular mass increases

Answer 7

1. intermolecular forces are stronger between molecules with a high relative molecular mass than between smaller molecules
2. because there are more points along the larger molecules for the intermolecular forces to act between them = more energy need to break forces

Question 8

what state are most simple molecular substances at room temp

Answer 8

liquid or gas

or easily melted solid

Question 9

why do giant covalent structures have high melting/boiling points

Answer 9

they have many strong covalent bonds which require large amounts of energy to be broken

Question 10

what state are giant covalent structures

Answer 10

solids

Question 11

describe common properties of giant covalent structures

Answer 11

1. don’t conduct electricity even when molten ( except graphite )
2. insoluble in water

Question 12

name 2 giant covalent structure and what is special about them

Answer 12

diamond
graphite

both made from only carbon atoms

Question 13

describe the structure of diamond and its physical properties as a result

Answer 13

1. carbons each form 4 covalent bonds
2. high melting point
3. strong covalent bonds hold atoms in a rigid lattice structure ( really hard)
4. doesn’t conduct electricity= no free electrons or ions

Question 14

describe the structure of graphite and its physical properties as a result

Answer 14

1. carbons each form 3 covalent bonds
2. graphite is soft + slippery
3. high melting point
4. non metal that conducts electricity

Question 15

why does graphite conduct electricity

Answer 15

only 3 out of 4 of carbons outer electrons are used in bonds= carbon atom has one delocolised electron = = free to move = graphite = non metal that conducts electricity

Question 16

why is graphite soft + slippery

Answer 16

carbons each form 3 covalent bonds= layers of carbon atoms= held together by weak intermolecular forces= free to slide over each other

Question 17

describe the structure of C 60 fullerene and its physical properties as a result

Answer 17

1. simple molecular substance
2. hollow spheres made up of 60 carbons
3. made up of large covalent molecules
4. molecules held together by intermolecular forces = can slide over each other = material = soft
5. each carbon has one delocalised electron ( like graphite )
6. electrons cant move between molecules = poor conductor of electricity