Answer:
1 oxygen atoms
Explanation:
When barium combines with oxygen to form an ionic compound, it will only require just an oxygen atom.
An ionic compound is formed due to the electrostatic attraction between oppositely charged ions
A metal loses electrons to be gained by the non - metal and in the process they attract each other with a force.
Barium has two valence electrons, to be stable, it loses the two;
Oxygen has six valence electrons, to be stable it will gain two valence electrons to form an octet.
So;
One barium atom will successfully bind with One oxygen atom to form
BaO
