In order to determine whether a bond is ionic or covalent, you need to know whether or not it is completely composed of nonmetal atoms or both metal and nonmetal ions.
Barium is a metal and Oxygen is a nonmetal, therefore there is no possible way they could bond unless they were attracted to opposite charges. Specifically, only if Barium becomes a cation and Oxygen becomes an anion then could they bond.
Now cation and anion both have the word "ion" in them, so therefore it must be an ionic bond.
Now we need to know the definition of a bond. A bond is formed when two elements are joined together by sharing their valence electrons.
Therefore, your answer should be:
Ionic, because valence electrons are shared.
Answer:
Francium is hypothesized to be the most reactive metal, but so little of it exists or can be synthesized, and the longest half-life of its most abundant isotope is 22.00 minutes, so that its reactivity cannot be determined experimentally.
Explanation:
Francium is an alkali metal in group 1/IA. All alkali metals have one valence electron. As you go down the group, the number of electron energy levels increases – lithium has two, sodium has three, etc..., as indicated by the period number. The result is that the outermost electron gets further from the nucleus. The attraction from the positive nucleus to the negative electron is less. This makes it easier to remove the electron and makes the atom more reactive.
Experimentally speaking, cesium (caesium) is the most reactive metal.
The temperatures increased
Since chromium has 24 as its atomic number (which mean that it has 24 proton and 24 electron in neutral ground state), the electron configuration for the chromium would be :
1s^2 , 2s^2 , 2p^6 , 3s^2, 3p^6 , 3d^5 , 4s^1