periodicity exam q's

Question 1

explain in terms of crystal structure and bonding why silicon oxide has a higher melting point than phosphorus oxide

Answer 1

• sio2 has a larger mr, so larger van der waals
• sio2 is macromolecular
• strong covalent bonds
• P4O10 simple covalent molecule

Question 2

formula of a hydroxide of an element in period 3, used in medicine

Answer 2

Mg(OH)2

Question 3

identify the element in period 3, that has the largest atomic radius

Answer 3

Na

Question 4

identify the element in group 5 period 3, and explain its ionization energy

Answer 4

phosphorous
- large jump in ionization energy for the 6th ionization energy
this is when an electron is being removed from the second energy level

Question 5

why the melting point of sulfur is greater than phosphorous

Answer 5

• more van der waals between molecules
• s molecules are bigger than p4 molecules

Question 6

explain why the melting point of magnesium is higher than the melting point of sodium

Answer 6

• mg2+ has a higher charge
• stronger attraction to delocalized sea of electrons

Question 7

state hats observed when dilute aq sodium hydroxide is added to magnesium and barium chloride

Answer 7

mgcl2 - white ppt
bacl2 - no change

Question 8

explain why the second ionisation energy of calcium is lower than the second ionisation energy of potassium

Answer 8

• more shielding in Ca+
• in ca+ outer electron is further away from the nucleus