Period 3 Elements

Question 1

What elements react with water

Answer 1

Sodium and magnesium

Question 2

Equation for sodium reacting with water

Answer 2

2Na(s) + 2H2O(l) → 2NaOH(aq) + H2(g)

Question 3

pH of sodium reacting with water

Answer 3

(pH of NaOH) 12-14

Question 4

Equation for Mg reacting with water

Answer 4

Mg(s) + 2H2O(l) → Mg(OH)2(aq) + H2(g)

Question 5

Equation for Mg reacting with steam

Answer 5

Mg(s) + H2O(g) → MgO(s) + H2(g)

Question 6

pH of reaction between Mg and water

Answer 6

(pH of Mg(OH)2) 9-10

Question 7

Charge on sodium and magnesium

Answer 7

Sodium loses one electron → Na+ ion
Magnesium loses two electrons → Mg2+

Question 8

Sodiums reaction with Oxygen equation

Answer 8

2Na(s) + 1⁄2O2(g)→ Na2O(s)

Question 9

Mg reaction with Oxygen equation

Answer 9

Mg(s) + 1⁄2O2(g) → MgO(s)

Question 10

Al reaction with Oxygen equation

Answer 10

2Al(s) + 1 1⁄2O2(g)→ Al2O3(s)

Question 11

Si reaction with Oxygen equation

Answer 11

Si(s) + O2(g)→ SiO2(s)

Question 12

P reaction with oxygen equation

Answer 12

P4(s) + 5O2(g) → P4O10(s)

Question 13

S reaction with Oxygen equation

Answer 13

S(s) + O2(g) → SO2(g)

Question 14

Sodiums reaction with Oxygen equation observation

Answer 14

vigorously, yellow flame, white solid

Question 15

Mg reaction with Oxygen equation observation

Answer 15

vig, wh, wh solid

Question 16

Al reaction with Oxygen equation observation

Answer 16

fast, wh, wh powder

Question 17

Si reaction with Oxygen equation observation

Answer 17

slow, wh sparkles, wh pow

Question 18

P reaction with oxygen equation observation

Answer 18

vig, wh, wh clouds

Question 19

S reaction with Oxygen equation observation

Answer 19

gentle, blue, toxic fumes

Question 20

Melting point trend

Answer 20

Na2O 1250
MgO 2750
Al2O3 2000
SiO3 1500
P4O10 250
SO3 0

Question 21

Describe the structure of the oxides

Answer 21

-Ionic
Na2O
MgO
Al2O3

-Giant Covalent
SiO2

-Simple molecular
P4O10
SO3

Question 22

Trend between covalent characters, ionic and pH

Answer 22

Covalent characters = increase going across
pH and ionic characters = decreases

Question 23

Why does Na2O, MgO and Al2O3 have high melting points

Answer 23

Giant Ionic Lattice
Strong forces of attraction , more energy harder break bonds

Question 24

Why does MgO have the highest melting point compared to Na2O

Answer 24

Forms 2+ ions, attracting O2- more stronger than Na 1+

Question 25

Why is Al2O3 melting point lower than expected

Answer 25

Bonds partially covalent
Electronegativity between Al and O isn’t as large as between Mg and O. O2– ions in Al2O3 can’t attract the electrons as strongly as in MgO.

Question 26

Why does SiO2 have higher melting points than other non-metal oxides

Answer 26

giant macromolecular structure
Giant macromolecular structure, higher melting points

Question 27

Why do P4O10 and SO3 have low melting points

Answer 27

weak intermolecular forces (dipole-dipole and van der Waals), which take little energy to overcome

Question 28

Atomic Radius trend

Answer 28

Nuclear charge increases, stronger electrostatic attraction between nucleus and valence electrons

Question 29

First ionisation energy trend

Answer 29

atomic radius decreases so the energy needed to remove an electron increases

decreases in the trend when you move to another sub-shell

Question 30

Electronegativity trend

Answer 30

Number of protons and nuclear charge increases

Greater electrostatic attraction between the nucleus and electrons