The First Ionization Energy of the First Six Elements in the Periodic

Multiple Choice

The first ionization energy of the first six elements in the periodic table is given below.

Why is the first ionization energy of B smaller than Be?

A) Because the first IE decreases as we go across a row of the periodic table from left to right.
B) Because the nucleus of a B (Z = 5) atom contains fewer protons than the nucleus of a Be (Z = 4) atom.
C) Because the outermost electron on B is coming from a 2p, not a 2s orbital.
D) Because the atomic number of B is odd, whereas the atomic number of Be is even.
E) For the same reason that the first IE of He is larger than that of H.