Question

which of these elements has the highest ionization energy?
francium (fr)
potassium (k)
sodium (na)
lithium (li)

Explanation:

Step1: Recall the trend of ionization energy in a group

Ionization energy generally decreases down a group in the periodic table. This is because as we move down a group, the atomic radius increases. The outermost electrons are farther from the nucleus and are less strongly attracted by the nucleus. So, it is easier to remove an electron (lower ionization energy).

Step2: Analyze the given elements

The elements \(Fr\), \(K\), \(Na\), \(Li\) are all in Group 1 (alkali metals) of the periodic table. \(Li\) is the highest (first - period element in this group), followed by \(Na\) (second - period), \(K\) (third - period), and \(Fr\) (seventh - period).

Answer:

Lithium (Li)