Question

which has the lowest ionization energy? (hint: remember that it has the same trend as electronegativity.)
boron (b)
neon (ne)
sodium (na)
chlorine (cl)

Explanation:

Step1: Recall ionization - energy trend

Ionization energy increases across a period and decreases down a group. It has the same trend as electronegativity.

Step2: Locate elements on periodic table

Boron (B) is in period 2, group 13. Neon (Ne) is in period 2, group 18. Sodium (Na) is in period 3, group 1. Chlorine (Cl) is in period 3, group 17.

Step3: Compare positions

Sodium is the most metallic among them as it is in the first - group and third period. Metals have lower ionization energies.

Answer:

Sodium (Na)