Question

The valencies for oxygen and aluminium are ______ and _______ respectively.

• A.
  3 and 3
• B.
  2 and 2
• C.
  3 and 2
• D.
  2 and 3

Answer 1

The correct option is D

2 and 3
For elements having valence electrons 1,2 or 3 . Valency is equal to the number of valence electrons.

Number of valence electrons in aluminum is 3, valency = 3.

For elements having valence electrons 4,5,6 or 7. Valency = 8 - number of valence electrons.

Number of valence electrons in oxygen is 6, valency = 8-6 =2.