Elements with high ionization energies would-------

Analyze the question: Ionization energy is the energy needed to remove the outermost electron from a gaseous atom. A high ionization energy means the electron is held tightly and is hard to remove. We need to pick the statement that goes with this.

Concept: The ionization energy depends on:

• Effective nuclear charge (Zeff): the higher the Zeff, the stronger the pull on the outer electron, so the ionization energy is higher.
• Atomic radius: the larger the radius, the weaker the pull, so the ionization energy is lower.
• Shielding: more inner shells mean more shielding and a lower ionization energy.

Evaluate each option:

• A. Lose electrons easily: Wrong. High ionization energy means electrons are lost with difficulty.
• B. Have large atomic radii: Wrong. Large atoms have outer electrons far from the nucleus, which gives low ionization energy (e.g. Cs, Fr).
• C. Have high effective nuclear charges: Correct. A strong net pull from the nucleus holds the outer electrons firmly, so more energy is needed to remove one. This is why ionization energy increases across a period, as Zeff rises and the radius shrinks.
• D. Have low atomic numbers: Not a reliable rule. Ionization energy generally decreases down a group, so low atomic number can go with high ionization energy (e.g. He), but atomic number alone does not decide it. Sodium (Z = 11) has a much lower ionization energy than neon (Z = 10) only because of the shell and nuclear charge effects. The direct cause is Zeff, not atomic number.

Answer: C. have high effective nuclear charges

Tip: Remember "High IE = tight grip." Anything that strengthens the nucleus's grip (high Zeff, small radius) raises the ionization energy. Anything that loosens it (large radius, more shielding) lowers it.