Aim for FiveChemistry

Short free-response question

Ionization energies across period 3

  • Unit 1
  • 4 points
  • About 9 minutes

You can use a calculator on this question, just like on exam day.

A shorter multipart question that sticks to one or two topics. Each part usually asks for one calculation, claim or explanation. On the exam: 4 questions (Questions 4–7), part of the 1-hour-45-minute free-response section; calculator allowed.

The question and its sources

The table gives ionization energies of three elements in period 3.

Table 1. Ionization energies

ElementFirst ionization energy (kJ/mol)Second ionization energy (kJ/mol)
Na4964562
Mg7381451
Al5781817

Source: Standard reference values, rounded

Suggested time: 9 minutes

Your answers are saved in this browser as you type.

Something wrong with this question?

What's wrong?

Please don't include personal details.

Part (a)

1 point

Explain why the first ionization energy of Mg is greater than that of Na. Use Coulomb's law and principles of atomic structure.

0 / 2,500 characters

Part (b)

1 point

Explain why the first ionization energy of Al is less than that of Mg, even though Al has a greater nuclear charge.

0 / 2,500 characters

Part (c)

1 point

Is the radius of an Mg²⁺ ion greater than, less than, or equal to the radius of an Mg atom? Justify your answer.

0 / 2,500 characters

Part (d)

1 point

The second ionization energy of Na is much greater than the second ionization energy of Mg, even though Mg has the greater nuclear charge. Explain this difference using principles of atomic structure.

0 / 2,500 characters

Checking scoring…

Scoring it yourself shows you the rubric, examples and a model answer. Try writing your answer first.