\[Sodium has a lower ionization energy than magnesium because its outermost electron is in a 3s orbital, which is farther away from the nucleus and experiences a lower effective nuclear charge compared to the 3s electrons in magnesium.\]

\[The reaction between zinc and dilute nitric acid produces hydrogen gas because zinc is more reactive than hydrogen and displaces hydrogen from the acid.\]

\[Zn + 2HNO3 → Zn(NO3)2 + H2\]

(a) Write an equation for the reaction between zinc and dilute nitric acid.

(b) Explain why the ionization energy of sodium is lower than that of magnesium.