Periodic Table Trends in 5 Minutes — Free Quick Revision
Learn Periodic Table Trends in about 5 minutes — a free bite-sized module with a clear explanation, a worked example and a quick quiz for Indian students.
TL;DR: Learn Periodic Table Trends in about 5 minutes — a free bite-sized module with a clear explanation, a worked example and a quick quiz for Indian stude…
Written & reviewed by the Syllab.in Academic Team (CBSE/NCERT subject experts) · Updated
Atomic radius increases down a group, electronegativity decreases. Across a period, radius decreases, ionization energy increases.
Chemistry · Class 11 · about 7 minutes
The Idea
The periodic table reveals patterns in how atomic properties change across groups (columns) and periods (rows).
Across a Period (left to right): - Atomic Radius decreases: More protons pull electrons closer. - Ionization Energy increases: Harder to remove an electron as it's held tighter. - Electronegativity increases: Atoms pull electrons more strongly in bonds.
Down a Group (top to bottom): - Atomic Radius increases: New electron shells are added, pushing electrons farther from nucleus. - Ionization Energy decreases: Valence electrons are farther away and easier to remove. - Electronegativity decreases: Distant valence electrons are less attracted to the nucleus.
These trends explain reactivity. Alkali metals (left of period, down the group) are very reactive because they have low ionization energy and give up electrons easily. Halogens (right of period, top of group) are reactive because they have high electronegativity and greedily pull electrons.
Worked Example: Compare Ionization Energies
Problem. Which element requires more energy to remove an electron: Na or Cl? Explain.
Solution.
Sodium (Na, atomic #11) and Chlorine (Cl, atomic #17) are both in period 3. Across a period, ionization energy increases.
Chlorine is to the right of sodium, so Cl has higher ionization energy. This is because Cl has a stronger nuclear charge (more protons) pulling on the valence electrons, and it's closer to having a full octet, so it holds onto electrons tightly.
Expected values: Na ≈ 495.8 kJ/mol, Cl ≈ 1251.2 kJ/mol. Cl >> Na in ionization energy.
Quick Quiz
Answer each one before reading the explanation beneath it.
1. Which of these elements has the largest atomic radius?
- Fluorine (F)
- Chlorine (Cl)
- Bromine (Br) — correct
- Iodine (I)
Bromine (Br)
2. Electronegativity of Ne is ~3.0, O is ~3.4. Is this consistent with periodic trends?
- Yes, O is to the left of Ne in period 2, but O > Ne in electronegativity
- No, Ne should have higher electronegativity since it's to the right
- Electronegativity values don't follow simple trends
- Yes, O is to the left but has higher because it forms bonds; Ne is inert — correct
Yes, O is to the left but has higher because it forms bonds; Ne is inert
3. Which element has the highest ionization energy?
- Neon (Ne) — correct
- Helium (He)
- Lithium (Li)
- Argon (Ar)
Neon (Ne)
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