Classification of Elements and Periodicity in Properties — Class 11 CBSE Chemistry revision notes
A 6-page visual revision sheet for Classification of Elements and Periodicity in Properties, written for Class 11 CBSE Chemistry. Formulas, diagrams and the traps that cost marks, laid out to be read the night before rather than the term before. Free, and it opens inside CapCompass.
Page 1 as PDF
Classification of Elements and Periodicity in Properties in one look
one law, one table, and every property tracing the same shape across it
A quick history, before Mendeleev
- Döbereiner's triads: three elements where the middle atomic mass ≈ average of the other two
- e.g. Li, Na, K; worked for only a few triads
- Newlands' law of octaves: by atomic mass, every eighth element repeated the first's properties
- like notes in music; broke down after calcium
- forced unrelated elements together just to keep the pattern
- Mendeleev's periodic law: properties are a periodic function of atomic mass
- he left gaps for undiscovered elements and predicted their properties correctly
- hydrogen's position never sat cleanly in the table
- Te/I had to break strict atomic-mass order (Te heavier, yet placed before I)
- kept to match chemical family: atomic mass wasn't quite the right basis
The modern periodic law
- Moseley refined it: properties are a periodic function of atomic number (Z), not mass
- this fixed every ordering problem Mendeleev's table had
- atomic number = number of protons; it fixes an element's identity and chemistry
- this is the law the modern periodic table is actually built on
How many elements per period
- Period 1: 2 elements
- Periods 2 & 3: 8 elements each
- Periods 4 & 5: 18 elements each
- Periods 6 & 7: 32 elements each (includes the f-block)
Page 1 of 6. The full sheet, all 6 pages, opens free in the app.
What this Classification of Elements and Periodicity in Properties sheet covers
- A quick history, before Mendeleev
- The modern periodic law
- How many elements per period
- Period 1
- Periods 2 & 3
- Periods 4 & 5
- Periods 6 & 7
- s, p, d, f blocks
- Atomic radius
- Across a period (left → right)
- Down a group (top → bottom)
- Ionic radius
- Cations vs their parent atom
- Anions vs their parent atom
- Worked: ranking an isoelectronic series by size
- Ionization enthalpy
- Where ionization enthalpy dips
- Electron gain enthalpy
- The halogen anomaly
- Electronegativity
- Metallic vs non-metallic character
- Valence and oxidation states
- Symbols & terms
- Traps that cost marks
- Tricks that save time
How CapCompass uses this sheet
These notes are not a standalone PDF. CapCompass plans Chemistry chapter by chapter against your real exam dates and free hours, and when the plan reaches Classification of Elements and Periodicity in Properties the sheet opens inside the study block itself — at the page covering the sub-topic that block is on, with the timer still running. Revision arrives at the moment the plan says revise, instead of having to be gone looking for.