chemical bonding and structure

Question 1

valency definition

Answer 1

number of electrons that must be gained, shared or lost in order for an atom to achieve a noble gas configuration

Question 2

definition of ionic bonding

Answer 2

the electrostatic force of attraction between 2 oppositely charged ions

Question 3

definition of covalent bonding

Answer 3

electrostatic force of attraction between a shared pair of electrons and the positive nuclei of 2 atoms

Question 4

definition of metallic bonding

Answer 4

electrostatic force of attraction between positively charged ions and a “sea” of delocalised electrons

Question 5

structure of ionic compounds

Answer 5

giant ionic (crystal) lattice structure

Question 6

structure of covalent compounds

Answer 6

simple covalent, giant covalent, macromolecules

Question 7

difference between simple covalent, giant covalent and macromolecules

Answer 7

simple covalent: simple molecules with a countable number of atoms in a fixed ratio
giant covalent: uncountable number of atoms
macromolecules: covalent molecules joined together into chains of larger molecules

Question 8

structure of metals

Answer 8

giant metallic lattice structure

Question 9

why do metals have delocalised electrons

Answer 9

due to metals being packed closely in a regular arrangement, metal atoms ‘lose’ their valence electrons and become positively charged ions. the electrons no longer ‘belong’ to any metal atom and can freely move around the metal ions

Question 10

similarities between ionic bonding, covalent bonding and metallic bonding

Answer 10

(strong) electrostatic forces of attraction, involve oppositely charged particles, can result in giant structures

Question 11

hardness of different molecular structures

Answer 11

giant ionic crystal lattice: hard and brittle
simple covalent molecular structure: soft
giant covalent structure: hard (except graphite)
macromolecular structure: varies
giant metallic crystal lattice: malleable and ductile

Question 12

why are giant ionic crystal lattice structures hard

Answer 12

the strong electrostatic forces of attraction between the oppositely charged ions causes them to resist motion and be resistant to deformation

Question 13

why are giant ionic crystal lattice structures brittle

Answer 13

when a strong enough force is applied, ions move away from their lattice positions and are displaced. when ions of the same charge from adjacent layers face each other, the strong repulsive forces causes the lattice structure to cleave evenly

Question 14

why are simple covalent structures soft

Answer 14

only a small amount of force is needed to overcome the weak intermolecular forces of attraction between the molecules

Question 15

why are giant covalent structures hard

Answer 15

a large amount of force is needed to break the numerous strong covalent bonds between the atoms present in the structure

Question 16

why is graphite soft unlike other giant covalent structures

Answer 16

layers of carbon atoms in graphite are held loosely by weak intermolecular forces of attraction and little force is required to overcome them, allowing them to slide over one another

Question 17

why are giant metallic structures malleable and ductile

Answer 17

the ‘sea’ of delocalised electrons in the lattice do not belong to any particular metal ion so if sufficient force is applied to the metal, layers of ions can slide over one another without disrupting the bonding

Question 18

malleable meaning

Answer 18

ability of a material to be hammered or pressed into shape without breaking or cracking

Question 19

ductile meaning

Answer 19

ability of a material to be drawn into a thin wire

Question 20

solubility of different structures in aqueous solvents

Answer 20

giant ionic crystal lattice: soluble except insoluble salts
simple covalent: insoluble except iodine, sugar, hcl, ammonia, carbon dioxide
giant covalent: insoluble
giant metallic lattice: insoluble

Question 21

why are ionic lattice structures soluble in aqueous solvents

Answer 21

“like dissolves like” polar substances dissolve in polar solvents

Question 22

solubility of different structures in organic solvents

Answer 22

giant ionic lattice: insoluble
simple covalent: soluble
giant covalent: insoluble
giant metallic lattice: insoluble

Question 23

why are simple covalent structures soluble in organic solvents

Answer 23

“like dissolves like”, non-polar substances dissolve in non-polar solvents

Question 24

electrical conductivity of different structures

Answer 24

giant ionic lattice: only in molten and aqueous states
simple covalent: poor in all states unless dissolved in water to form solutions with ions that can conduct electricity
giant covalent: poor except graphite
giant metallic lattice: good in solid and molten states

Question 25

why can giant ionic lattice structures conduct electricity in molten and aqueous states

Answer 25

thereare mobile ions that can conduct electricity as the ionic compund can dissociate in water to form ions (aqueous) or the large amount of energy can overcome the strong electrostatic forces of attraction between oppositely charged ions (molten). aka the ions are no longer held in fixed positions and can move around and conduct electricity

in solid state, ions are held in fixed positions by electrostatic forces of attraction and cannot move.

Question 26

why are simple covalent structures poor electrical conductors

Answer 26

there are no mobile ions and electrons / mobile charge carriers to conduct electricity

Question 27

why are giant covalent structures poor electrical conductors

Answer 27

there are no mobile ions and electrons / mobile charge carriers to conduct electricity

Question 28

why is graphite a good electrical conductor

Answer 28

graphite is comprised of carbon atoms with 4 valence electrons. each carbon atom only bonds to 3 others, leaving one unbonded valence electron per atom that is mobile within the layer to conduct electricity

Question 29

why can giant metallic lattice structures conduct electricity in solid and molten states

Answer 29

there will be mobile electrons that can move around and conduct electricity

Question 30

melting and boiling points of different structures

Answer 30

giant ionic lattice: high
simple covalent: low
giant covalent: high
giant metallic lattice: high

Question 31

why do giant ionic lattice structures have high melting and boiling points

Answer 31

a large amount of energy is required to overcome the strong electrostatic forces of attraction between oppositely-charged ions

Question 32

why do simple covalent structures have a low melting and boiling point

Answer 32

only a small amount of energy is required to overcome the weak intermolecular forces of attraction between molecules

Question 33

why do giant covalent molecules have a high melting and boiling point

Answer 33

a large amount of energy is required to overcome the strong covalent bonds between atoms

Question 34

why do giant metallic lattice structures have a high melting and boiling point

Answer 34

a large amount of energy is required to overcome the strong electrostatic forces between the positive ions and sea of delocalised electrons

Question 35

why do alloys have lower melting and boiling points than pure metals

Answer 35

the presence of other elements in the alloy acts as impurities which lowers melting point. the different sizes of atoms in an alloy also make the lattice arrangement less regular than a pure metal, making bonds between atoms weaker and also lowering melting point

Question 36

why can alloys conduct electricity

Answer 36

the presence of a ‘sea’ of delocalised electrons act as mobile charge carriers that allow the alloy to conduct electricity

Question 37

why are alloys not very malleable and ductile

Answer 37

the different sizes of atoms disrupt the regular lattice arrangement of pure metals, hence layers of atoms cannot slide over each other easily