Question

Consider the group 1A element sodium (atomic number 11), the group 3A element aluminum (atomic number 13), and the group 7A element chlorine (atomic number 17). These elements are in period 3. How are the first ionization energies of these elements related? A. sodium > aluminum > chlorine B. sodium < aluminum < chlorine C. sodium < chlorine < aluminum D. sodium > chlorine > aluminum

Answer 1

B. sodium < aluminum < chlorine

Ionization energies increase from left to right in the Periodic Table.  

These elements are all in Row 3 of the Periodic Table.

Na is furthest left, so it has the lowest ionization energy.

Cl is furthest right, so it has the highestionization energy.

Thus, the order is Na < Al < Cl .