Properties of Period 3 elements and their oxides

Question 1

how do Na and Mg react?

Answer 1

both react ionically to form positive ions

Question 2

which is more reactive, Na or Mg, and why?

Answer 2

Na is more reactive than Mg because it only has to lose one electron (whereas Mg has to lose two) so less energy is required to ionise it

Question 3

what do the period 3 elements react with oxygen to form?

Answer 3

oxides in their highest oxidation state

Question 4

what are the oxides that form form the period 3 elements:
- phosphorus
- aluminium

Answer 4

P4O10
Al2O3

Question 5

what is required for sulfur trioxide (SO3) to form?

Answer 5

high temperatures and a catalyst

Question 6

what affects the reactivity and melting points of the period 3 oxides?

Answer 6

structure and bonding

Question 7

the reaction of Mg with water

Answer 7

Mg + 2H20 –> Mg(OH)2 + H2

Question 8

the reaction of Mg with steam

Answer 8

Mg + H20 –> MgO + H2

Question 9

how does Mg react with water?

Answer 9

very slowly

Question 10

how does Mg react with steam?

Answer 10

vigorously, burning with a bright white flame

Question 11

how does Na react with cold water?

Answer 11

vigorously, with lots of fizzing

Question 12

how do the period 3 elements react in air?

Answer 12

Na, Mg, P and S react readily
Al and Si react slowly

Question 13

what are Na2O, MgO and Al2O3?

Answer 13

ionic oxides (metal + non-metal)

Question 14

why does MgO have a higher melting point than Na2O?

Answer 14

the Mg2+ ions are more strongly attracted to the oxygen than the Na+ ions

Question 15

why do P4O10 and SO2 have low melting points?

Answer 15

they form simple molecular structures held together by VDWs and dipole-dipole forces (weak IMFs)

Question 16

why does SiO2 have a higher melting point than the other non-metal oxides?

Answer 16

it has a giant macromolecular structure containing strong covalent bonds which require a lot of energy to overcome

Question 17

why does Al2O3 have a lower than expected melting point?

Answer 17

because there is a smaller difference in electronegativity between Al and O so the oxygen ions don’t attract the electrons in the metal-oxygen bond as strongly as in MgO

Question 18

what are the bonds in Al2O3?

Answer 18

partially covalent

Question 19

are covalent oxides alkaline or acidic?

Answer 19

acidic

Question 20

is Al2O3 soluble in water

Answer 20

no Al2O3 is insoluble in water due to its slight covalent character

Question 21

acid + base –> ?

Answer 21

acid + base –> salt + water

Question 22

what does it mean if a compound is amphoteric?

Answer 22

it can react as an acid and as a base

Question 23

basic oxides neutralise ?

Answer 23

basic oxides neutralise acids

Question 24

acidic oxides neutralise ?

Answer 24

acidic oxides neutralise bases

Question 25

amphoteric oxides neutralise ?

Answer 25

amphoteric oxides neutralise acids and bases

Question 26

do Na2O, MgO and Al2O3 have high or low melting points? why?

Answer 26

high melting points because they form giant ionic lattices

Question 27

what solutions form when ionic oxides react with water?

Answer 27

alkaline solutions because the O2- ions accept H+ ions from the water molecules to form OH- ions

Question 28

why is the solution formed when MgO reacts with water less alkaline than when Na2O reacts with water?

Answer 28

Na2O is more soluble in water so more OH- are produced

Question 29

what do simple covalent oxides form when added to water? why?

Answer 29

acidic solutions because they react to form an acid which then dissociates to release H+ ions

Question 30

what are P4O10 and SO2?

Answer 30

simple covalent oxides

Question 31

phosphorus oxide + water --> ?

Answer 31

phosphorus oxide + water --> phosphoric acid (H3PO4)

Question 32

sulfur dioxide + water --> ?

Answer 32

sulfur dioxide + water --> sulphuric (IV) acid (H2SO3!)

Question 33

sulfur trioxide + water --> ?

Answer 33

sulfur dioxide + water --> sulphuric acid (VI) (H2SO4!)

Question 34

how does SiO2 react with water?

Answer 34

SiO2 is insoluble in water because it's many strong covalent bonds take a lot of energy to overcome

Question 35

what is SiO2 classed as?

Answer 35

an acid because it will react with a base to form a salt

Question 36

what is Al2O3 classed as?

Answer 36

amphoteric as t all react with both acids and bases to form a salt

Question 37

when aluminium oxide is acting as an acid and reacts with a base, no ? is produced

Answer 37

no water is produced - only the salt