Question

What trend in ionization energy occurs across a period on the periodic table?

Answer 1

The trend  in ionization energy that occurs  across  a period   on  periodic table is that

Ionization  energy of elements within a period  generally increases  from left to the right.

explanation

 Ionization energy  is energy  required to remove an electron from gaseous  atom or ion.

 The  ionization energy  increase across the period because, as  you move  across  the period (from the left to  the right)   the atomic radius  decrease.  

This make outer  electrons to be  closer to the nucleus and more attracted to the  center.Therefore it is hard to remove electron  as you move across the period.