periodicity

Question 1

How does the atomic radius (a measure of the
size of atoms) across each period?

Answer 1

decreases
- nuclear charge increases pulling electrons in closer
- similar sheilding across no so additional shells to screen outer electrons
- atom becomes constricted

Question 2

period 3

Na,Mg,Al

bonding structure, forces , melting points

Answer 2

• bonding structure - Giant metallic lattice – positive metal ions surrounded by a sea of delocalised electrons
• forces - Strong electrostatic forces between the positive metal ion and delocalised electrons.
• melting points - high melting points - increasing across group

Question 3

period 3

Si

bonding structure, forces , melting points

Answer 3

• bonding structure - Giant covalent Macromolecular
• forces - Many strong covalent bonds – lots of energy required to overcome these
• melting points - highest melting point

Question 4

period 3

Si

bonding structure, forces , melting points

Answer 4

• bonding structure - Giant covalent Macromolecular
• forces - Many strong covalent bonds – lots of energy required to overcome these
• melting points - highest melting point

Question 5

period 3

P

bonding structure, forces , melting points

Answer 5

• bonding structure - P4 , Simple molecular
• forces - Weak intermolecular forces – Van der Waals forces
• melting points - low melting point

Question 6

period 3

S

bonding structure, forces , melting points

Answer 6

• bonding structure - S8 , Simple molecular
• forces - Weak intermolecular forces – Van der Waals forces stronger than for P as larger molecule
• melting points - low melting point

Question 7

period 3

Cl

bonding structure, forces, melting points

Answer 7

• bonding structure- Cl2 Simple molecular
• forces - Weak intermolecular forces – Van der Waals forces -Smaller than P so weaker forces
• melting points - lowest

Question 8

period 3

Ar

bonding structure, forces, melting points

Answer 8

• bonding structure- atomic
• forces- Very weak forces between the atoms
• melting points - lowest

Question 9

period 3

trends in melting points

Answer 9

• increases due to the more delocalised electrons present and greater nuclear charge from Na,Mg,Al
• si forms giant covalent lattices with many strong covalent bonds
• dcreases for the rest as they are allsimple molecular with weak VDW forces
• Al deviates so does S

Question 10

Why does Al deviate

Answer 10

The outer electron is being removed from a 3p orbital
• The 3p orbital is further away from the nucleus than the 3s orbital

Question 11

Why does sulphur deviate ?

Answer 11

• Sulfur has a 3p orbital containing two electrons
• The spin repulsion between them decreases the energy required to remove one of them

Question 12

Conductivity of period 3

Answer 12

• Al,Mg,Na - all good conductors due to metalic structure
• Si - semi-conduuctor
• the rest do not conduct because they are simple molecules - no free electrons or ions