If barium was to react with oxygen to form ionic compounds, how many oxygen atoms would be needed? Explain.

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

its first and third is your answer i did the qustion the fourth isnt right