3.1.1—Organization

Feature	Meaning
Period	Row; highest occupied main energy level
Group	Column with related valence pattern
Block	Region associated with the outermost s, p, d, or f subshell
Region	Metals, metalloids, and non-metals occupy characteristic areas

Use the table's row, column, and block together; do not substitute period number for group or block identity.

Use bromine as a three-coordinate check: it lies in period 4, group 17 and the p block, so its outer shell is n = 4 with a p-subshell being filled. Block describes the subshell pattern, period the highest occupied main level, and group the repeating valence pattern—three related but different labels.

Representative question

[Maximum number: 1]

Which statements are correct regarding the organization of elements in the periodic table?

I. Elements with atomic numbers 4, 12 and 20 have atoms with the same number of energy levels occupied with electrons.
II. Elements with atomic numbers 9,17 and 35 have atoms with the same number of electrons in the outer shell.
III. The periodic table is divided into blocks based on the sub-levels occupied by electrons.

I and II only

I and III only

II and III only

I, II and III

Retrieve the route: locate an element from configuration, explain periodic and group trends, write oxide/reaction and oxidation-state answers, then connect incomplete d-sublevels to transition properties, ion configurations, and colours.

Check that every trend explanation names its particle-level cause, every equation is balanced, every oxidation state is a formal charge convention, and every transition colour uses absorbed/observed complementarity.

3.1.1—Organization

Periodic-Table Organization

Reading the Periodic Table

Assessment in practice

The Periodic Table Summary

Question 1