Can someone please help me with this question?

Propose a possible explanation as to why this trend exists. What characteristics of the elements lead to this trend?

We are discussing Ionization energy!
She's asking for characteristics like subatomic attractions, electron configurations, etc.

I just don't know were to begin...please help me! Thanks so mcuh!

2 answers

ionization energy is the energy to remove an electron. The further an electron is from the nucleus, the less is ionization energy. So atom size is a predominate factor.
As you go down a column (group, family) on the periodic table, the number of electron shells increases "shielding" the nucleus and weakening its attraction on outer (valence) electrons.
As you go from left to right on a row (period), the nuclear charge increases but electrons are added on the same shell. The nuclear attraction of valence electrons increases.