Question

of the following elements, which one has the smallest first ionization energy?
silicon
boron
carbon
aluminum

Explanation:

Ionization energy generally increases across a period (from left to right) and decreases down a group in the periodic table. Boron (\(B\)), carbon (\(C\)) are in period 2, while aluminum (\(Al\)) and silicon (\(Si\)) are in period 3. Among these, \(Al\) is the left - most in its period (period 3) compared to \(Si\). Also, \(Al\) is below \(B\) (group 13). Since ionization energy decreases down a group and from right to left across a period, \(Al\) has the lowest first ionization energy among the given elements.

Answer:

aluminum