Is it easier or harder to remove an electron from an atom if it has a lower ionization energy?

1 Answer
Nov 3, 2016

Answer:

Clearly it is easier to remove an electron with a lower ionization energy. We expend less energy.

Explanation:

We typically measure the ionization energies of (gaseous) atoms:

#"Atom(g)"+Deltararr"Atomic cation(g)"+"electron"#

When #Delta# is quoted in #kJ*mol^-1# this the #"first ionization enthalpy"#

Ionization energies typically INCREASE across a Period (looking at the Table from left to right), but DECREASE down a Group.

Why should this be so?