Question

Which element has the higher ionization energy; boron or oxygen?

Answer 1

Well, which has higher atomic number? `B,` `Z=5`; `O,` `Z=8`

Explanation:

We interrogate the process:

`"Atom(g) + energy"` `rarr` `"Atom"^+(g) + "electron"`

Because oxygen has the higher atomic number, and is in the same Period, I am willing to bet that it has a higher first ionization energy.

See here.