The type of oxide formed by the element among Li, Na, Be, Mg, B and Al that has the least atomic radius is :
- AO
- AO2
- A2O
- A2O3
Answer
(4) A2O3
Solution
Radius falls across a period and rises down a group: Li 152 > Be 111 > B 88 pm; Na 186 > Mg 160 > Al 143 pm.
B is smallest overall (Al lies below B) and is trivalent: 4B+3O2 2B2O3 ⇒ A2O3.
Answer: (4)