Question

an element X2O belongs to the third period of the periodic table.

A) write the atomic number and valency of the metal

B) is this oxide acidic or basic in nature?

Answer 1

As, the element X, on combination with oxygen forms a compound with a molecular formula X₂O. Therefore the valency of the element is 1.
As the element is present in the 3rd period therefore, it could be Na or Cl because both these elements have a valency of 1.
Since X is used before oxygen in oxide formula theretofore X should have a positive valency.
Hence X is sodium .i.e. Na.
1. The valency of Na is 1 and its atomic number is 11.
2. As the oxide of metals is basic, therefore Na₂O is also basic in nature.
As we go from left to right in a period, the basicity of oxides decreases or we can say the acidity of oxide increases.