Which of the following elements will have a lower ionization energy than scandium (Sc)?

• A. Iron (Fe)
• B. Zinc (Zn)
• C. Potassium (K)
• D. Aluminum (Al)

Answer: (C)

Verified step by step guidance

1. Recall that ionization energy is the energy required to remove an electron from a gaseous atom or ion. Generally, ionization energy increases across a period (left to right) and decreases down a group (top to bottom) in the periodic table.
2. Identify the position of scandium (Sc) in the periodic table: Scandium is in period 4 and group 3 (a transition metal).
3. Compare the positions of the given elements relative to scandium: Potassium (K) is in period 4 but group 1 (to the left of Sc), Iron (Fe) is in period 4 and group 8 (to the right of Sc), Zinc (Zn) is in period 4 and group 12 (further right), Aluminum (Al) is in period 3 and group 13 (above and to the left).
4. Use periodic trends to predict ionization energies: Elements to the left of Sc in the same period generally have lower ionization energies because they have fewer protons and less effective nuclear charge holding the electrons. Elements to the right usually have higher ionization energies. Also, elements in higher periods (lower rows) tend to have lower ionization energies due to increased electron shielding.
5. Conclude that Potassium (K), being to the left of Sc in the same period and an alkali metal, will have a lower ionization energy than scandium, while Iron (Fe), Zinc (Zn), and Aluminum (Al) will have higher ionization energies.