Periodicity

Question 1

State the meaning of periodicity

Answer 1

Repeating trends

Question 2

State the meaning ionisation energy

Answer 2

The minimum amount of energy required to remove one mole of electrons from one mole of gaseous atom to form (one mole of gaseous +1 ions )

Question 3

Define atomic radius

Answer 3

Total distance from the nucleus of an atom to the outer shell of the electron

Question 4

State the largest atomic radius in period 3

Answer 4

Na
-smallest nuclear charge
- sheilding stays the same

Question 5

State the trend in atomic radius across the period

Answer 5

-Atomic radius decreases
-Nuclear charge increases
-Shielding stays constant
-Same energy level

Question 6

State the trend in atomic radius down the group

Answer 6

Atomic radius increase
-electron shell is added
- increasing the distance between the outer electron and the nucleus reducing the power of attraction
- increase in shielding

Question 7

State the trend in atomic radius down the group

Answer 7

Atomic radius increase
-electron shell is added
- increasing the distance between the outer electron and the nucleus reducing the power of attraction
- increase in shielding

Question 8

Explain why the atomic radius decreases across period 3 from Na to cl (3 marks )

Answer 8

• nuclear charge increase
• shielding is constant
  -same number of shells

Question 9

Identify the element in period 4 with the largest atomic radius (3marks )

Answer 9

Potassium
-smallest nuclear charge
-shielding remains constant

Question 10

Deduce which of Na* and mg2* is the smaller ion (2marks )

Answer 10

Mg2*
-has more protons with the same number of shielding

Question 11

State the trend in ionisation energy across the period

Answer 11

-Increases
-atomic radius decrease
-nuclear charge increase
-outer electron held more strongly more energy required to remove the outer electron and ionise

Question 12

State the trend in ionisation energy down the group

Answer 12

-Decreases
-nuclear attraction between the nucleus and outer electrons reduces
- shielding increases
-less energy required to remove outer electrons

Question 13

Explain why there’s a decrease in ionisation energy from mg to Al

Answer 13

-Outer electron in the 3p orbital for Aluminium which is higher in energy compared to 3s
-increase shielding

Question 14

State the element in period 3 that has the highest first ionisation energy

Answer 14

• argon
  -largest nuclear charge
  -energy levels are the same

Question 15

Write an equation to represent the process when the first ionisation energy for sodium is measured

Answer 15

Na(g) ~> Na*(g) + e~

Question 16

Explain why the first ionisation energy of sultry is different from that of phosphorus (2 makrs )

Answer 16

-electron in 3p orbital for sulfur is paired
-repulsion occurs for paired electron
-3p4 is easier to remove then 3p3

Question 17

What happens to melting points across period 3 between sodium and aluminium

Answer 17

Na,Mg,Al
-general increase
-metallic bonding
-melting points increase due to increase in positive charge
-increases the electrostatic attraction forces more energy required to overcome these forces

Question 18

Which element in period 3 has highest melting point

Answer 18

Silicon

Question 19

Which element in period 3 has the lowest melting point

Answer 19

Argon

Question 20

State the element in period 3 that has the highest melting point (3 marks )

Answer 20

-Silicon
-covalent bonds
-strong covalent bonds needs to be broken
-requires a lot of energy to break the covalent bonds

Question 21

Explain what happens between p,s,cl
ar In terms of melting points

Answer 21

Huge decrease from silicon to phosphorus
- silicon higher as is s8 rather then p4
Larger covalent then p4
Stronger vdw forces
Cl - is low as gas at room temp
Argon - is lowest - noble gas weak vdw

Question 22

Explain in therms of structure and bonding , why the melting point of carbon is high (3 marks )

Answer 22

• macromolecules
  -covalent bonds in structure
  -string covalent bonds must be broken to break these bonds requires alot of energy