Periodic Trends Worksheet with Answers (Grade 11 Chemistry)

This free periodic trends worksheet helps Grade 11 students master the four big patterns on the periodic table: atomic radius, ionization energy, electronegativity and metallic character.

In this periodic trends worksheet, students fill in a trend table, rank elements, compare atoms and ions, explain trends in terms of effective nuclear charge and shielding, and analyse real ionization energy data. A complete answer key is included.

• Grade 11 · SCH3U
• 30 marks
• 30–40 minutes
• Answer key included

What's in This Periodic Trends Worksheet

The questions move from recall to reasoning, so one sheet covers a lesson check, homework and test review.

Part	Skill practised	Marks
A	Complete the trend table (across a period and down a group)	8
B	Rank elements and ions by radius, ionization energy, electronegativity and metallic character	8
C	Compare atoms and ions, and give a reason	4
D	Explain trends using effective nuclear charge and shielding	3
E	Successive ionization energies (data analysis)	3
F	Challenge: the Mg/Al and N/O exceptions	2
G	Linking trends to reactivity	2

The content matches the Ontario SCH3U expectations for periodic trends in the Matter, Chemical Trends and Chemical Bonding unit, and it suits any introductory chemistry course.

The Four Periodic Trends at a Glance

Every question in this periodic trends worksheet comes back to one map. Students can keep it beside them as they work.

Property	Across a period (left → right)	Down a group
Atomic radius	Decreases	Increases
First ionization energy	Increases	Decreases
Electronegativity	Increases	Decreases
Metallic character	Decreases	Increases

Two more patterns follow from these. Reactivity of metals increases down a group because ionization energy falls. Reactivity of non-metals increases up a group because electronegativity rises.

Why Periodic Trends Happen

Students who memorise the arrows without the reasons get stuck on Part D. Two ideas explain almost everything on the periodic trends worksheet:

• Effective nuclear charge (Z_eff). Across a period, each element adds one proton, while the new electron goes into the same energy level. The valence electrons feel a stronger pull, so atoms shrink and hold their electrons more tightly.
• Energy levels and shielding. Down a group, each element adds a whole energy level. Valence electrons sit farther out and are shielded by more inner electrons, so they are easier to remove.

For a refresher on where groups and periods sit, see our guide on how to read the periodic table. The trends also build directly on configurations, so the electron configuration worksheet is a good warm-up. For actual values, Ptable shows radius, ionization energy and electronegativity for every element, and the Wikipedia article on periodic trends covers the theory in more depth.

Periodic Trends Practice Questions

These are the same questions as in the periodic trends worksheet PDF. Work through them, then open the answer boxes to check.

Part A – Complete the Trend Table

Write increases or decreases in each cell.

Property	Across a period (left → right)	Down a group
Atomic radius	?	?
First ionization energy	?	?
Electronegativity	?	?
Metallic character	?	?

Part B – Rank the Elements

9. Atomic radius, smallest → largest: Na, Mg, Cl
10. Atomic radius, smallest → largest: K, Li, Na
11. First ionization energy, lowest → highest: P, Na, Al
12. First ionization energy, lowest → highest: Cl, Br, F
13. Electronegativity, lowest → highest: O, C, N
14. Electronegativity, lowest → highest: Mg, Ba, Ca
15. Metallic character, least → most: Na, Si, Al
16. Ionic radius, smallest → largest: Na⁺, Al³⁺, Mg²⁺

Part C – Which Is Larger? Give a Reason

17. Cl or Cl⁻
18. Na or Na⁺
19. O²⁻ or F⁻
20. K or Ca

Part D – Explain the Trend

21. Why does atomic radius decrease from Na to Cl across period 3?
22. Why does first ionization energy decrease down Group 1 (Li → Cs)?
23. Why does each noble gas have the highest first ionization energy in its period?

Part E – Successive Ionization Energies

Element X has these ionization energies (kJ/mol):

IE1	IE2	IE3	IE4
738	1451	7733	10 543

24. How many valence electrons does element X have?
25. Which group is X in? If X is in period 3, name it.
26. Explain the large jump between IE₂ and IE₃.

Part F – Challenge: The Exceptions

27. Aluminum is to the right of magnesium, yet its first ionization energy is lower (578 vs 738 kJ/mol). Explain.
28. Oxygen's first ionization energy is lower than nitrogen's (1314 vs 1402 kJ/mol). Explain.

Part G – Trends and Reactivity

29. Which is more reactive, sodium or potassium? Use a trend to justify.
30. Which is more reactive, fluorine or chlorine? Use a trend to justify.

Periodic Trends Worksheet Answer Key

Open each part to check your answers. The printable answer key is on pages 3–4 of the PDF.

Part A answers (Q1–8)

Property	Across a period (left → right)	Down a group
Atomic radius	Decreases	Increases
First ionization energy	Increases	Decreases
Electronegativity	Increases	Decreases
Metallic character	Decreases	Increases

Part B answers (Q9–16)

9. Cl < Mg < Na
10. Li < Na < K
11. Na < Al < P
12. Br < Cl < F
13. C < N < O
14. Ba < Ca < Mg
15. Si < Al < Na
16. Al³⁺ < Mg²⁺ < Na⁺

Part C answers (Q17–20)

17. Cl⁻: same 17 protons, one extra electron adds repulsion
18. Na: Na⁺ has lost its entire third energy level
19. O²⁻: both have 10 electrons, but O has fewer protons (8 vs 9)
20. K: same energy level, but K has one fewer proton (lower effective nuclear charge)

Part D answers (Q21–23)

21. Each element adds a proton, so effective nuclear charge increases. Electrons go into the same energy level with little extra shielding, so they are pulled closer to the nucleus.
22. The valence electron is in a higher energy level, farther from the nucleus and shielded by more inner electrons, so it is held less tightly and is easier to remove.
23. It has the greatest effective nuclear charge in the period and a full, stable valence shell, so removing an electron takes the most energy.

Part E answers (Q24–26)

24. 2
25. Group 2; magnesium (Mg)
26. The third electron must come from a full inner energy level (n = 2), which is closer to the nucleus and less shielded.

Part F answers (Q27–28)

27. Al loses a 3p electron, which is higher in energy and partly shielded by the 3s electrons, so it is easier to remove.
28. Oxygen's fourth 2p electron is paired in an orbital; repulsion between the paired electrons makes it easier to remove.

Part G answers (Q29–30)

29. Potassium: lower first ionization energy, so it loses its valence electron more easily.
30. Fluorine: smaller atom and higher electronegativity, so it gains an electron more easily.

5 Common Periodic Trends Mistakes

These come up every year in Grade 11 chemistry. Parts C, D and F of the periodic trends worksheet are designed to catch them.

1. Thinking more protons means a bigger atom. Across a period, more protons pull electrons closer, so the atom gets smaller.
2. Mixing up ionization energy and electronegativity. Ionization energy is about removing an electron from a lone atom. Electronegativity is about attracting shared electrons in a bond.
3. Forgetting ions change size. Cations are smaller than their atoms and anions are larger. In an isoelectronic series, more protons means a smaller ion.
4. Explaining with "because it's on the right." Position is not a reason. Full marks need effective nuclear charge, shielding or energy level.
5. Missing the exceptions. Mg → Al and N → O both break the ionization energy trend, and both are explained by sublevel structure.

How to Use This Periodic Trends Worksheet in Class

As a teacher, I use the sheet in three ways depending on where students are in the unit:

• Lesson practice: Assign Parts A–C right after teaching the trends. They take about 15 minutes.
• Homework: Send Parts D–G home. The explanation and data questions show who understands the reasons, not just the arrows.
• Unit review: Use the whole sheet as a timed review, then follow up with an online quiz for instant feedback.

To check mastery, pair it with our periodic table trends quiz (20 auto-graded questions), then move on to the ionic vs covalent bonding quiz, which uses electronegativity directly.

Frequently Asked Questions

Is this periodic trends worksheet free?

Yes. The worksheet and answer key are free to download and print as a PDF, with no account needed.

What are the four main periodic trends?

Atomic radius, first ionization energy, electronegativity and metallic character. Radius and metallic character increase down a group and decrease across a period; ionization energy and electronegativity do the opposite.

Why does atomic radius decrease across a period?

Each element adds a proton, raising the effective nuclear charge, while electrons are added to the same energy level. The stronger pull draws the electron cloud closer to the nucleus.

Why is the first ionization energy of aluminum lower than magnesium?

Aluminum loses a 3p electron, which is higher in energy and partly shielded by the filled 3s sublevel, so it takes less energy to remove than one of magnesium's 3s electrons.

What grade is this periodic trends worksheet for?

It is written for Grade 11 chemistry (Ontario SCH3U) and suits any introductory high school chemistry course.

More Free Grade 11 Chemistry Resources

• Electron Configuration WorksheetThe step before periodic trends
• Lewis Structures WorksheetBonding practice
• Chemical Bonding Quiz20 auto-graded questions
• Group and Period Number WorksheetGrade 9 refresher
• All Grade 11 ResourcesWorksheets and quizzes

Ready to practise? Download the free periodic trends worksheet PDF (use the Download button above), print it double-sided, and keep the answer key pages for marking.