periodicity

Question 1

Explain, in terms of crystal structure and bonding, why silicon(IV) oxide has
a higher melting point than phosphorus(V) oxide.

Answer 1

• SiO2 is macromolecular
  -more energy is required to break the covalent bonds
  -phosphorus is held by weak van der waals forces between molecules
  -these forces are easily broken

Question 2

what does a big jump in ionisation energy suggest

Answer 2

This is when the electron is being removed from the 2nd (principle)
energy level

Question 3

Explain why the atomic radius decreases across Period 3, from sodium to
chlorine.

Answer 3

The number of protons increases OR nuclear charge increases

Shielding is similar

Question 4

trend for atomic radius as you go down the group

Answer 4

• the number shells increase as you go down the group
  -the attraction between outer electron decreases
• increased shielding

Question 5

trend for atomic radius as you go across the period

Answer 5

-increased nuclear charge
-outer electron is drawn closer to nucleus due to increased attraction

Question 6

what is periodicity

Answer 6

repeating pattern or trends of physical and chemical properties

Question 7

what is the trend for ionisation energy as you go along the group

Answer 7

There is a decrease in atomic radius as you go along and increased proton charge ,

meaning electrons are held closely together ,requiring more energy to remove outer electron

Question 8

what is trend for ionisation energy as you go down the group

Answer 8

There is increased shielding meaning there is a smaller attraction between outer electron and positive nucleus.
Meaning less energy is required to remove outer electron

Question 9

what is the trend for melting point for across the period between the first three elements

Answer 9

melting point increased due to greater positive charge.
more electrons are released as free electrons so attractive electrostatic forces increase.
making the bonds harder to break

Question 10

describe the trend for the rest of the elements of period three

Answer 10

silicon is a macro molecular
it has a covalent structure which requires a lot of energy to break the bonds.

and the other elements are held by weak vander waals forces.

Question 11

sodium reaction with water

Answer 11

2Na+2H2O—->2NaOH+H2

PH 13-14

Question 12

magnesium reaction with water

Answer 12

Mg(s)+2H2O(l)–>Mg(OH)aq2+H2(g)

PH 10 (less alkalline due to its insolubility)

reacts slow with cold water

Question 13

magnesium react with steam

Answer 13

mg(s)+H2O(g)–>MgO(s)+H2
reacts faster with steam and heat

Question 14

chlorine react with water

Answer 14

Cl2(g) +H2O(l)—>HClO(aq)+HCl(aq)

chlorine dissolves in H2O

Question 15

State one observation when magnesium reacts with steam.

Answer 15

• state one observation when magnesium reacts with steam.
• Mg(s) + H2O(g) → MgO(s) + H2(g)

Question 16

Explain, in terms of structure and bonding, why magnesium chloride has a
high melting point.

Answer 16

(Giant) ionic lattice / lots of Mg2+ and Cl–
ions

Strong (electrostatic) forces of attraction

Between Mg2+ and Cl–
ions

Question 17

Explain why the melting point of magnesium is higher than the melting
point of sodium.

Answer 17

Mg2+ has a higher charge than Na+

Stronger attraction to delocalised sea of electrons /

Question 18

Explain why the second ionisation energy of calcium is lower than the
second ionisation energy of potassium.

Answer 18

Ca(+) loses electron from a 4(s) orbital or 4th energy level or 4th
energy shell a

Ca(+) loses electron from a 4(s) orbital or 4th energy level or 4th
energy shell a

Question 19

Explain, in terms of oxidation states, why magnesium is the reducing
agent.

Question 20

Explain why the melting point of calcium sulfate is high

Answer 20

Strong attraction

Between positive and negative ions