Chemistry — Atoms and Molecules

Overview

Atoms and Molecules form the foundational chapter for understanding all of chemistry at the upper-primary level. This topic appears consistently in KAR TET Paper II (Mathematics and Science) and tests your grasp of atomic structure, subatomic particles, electron arrangement, and how atoms combine to form molecules. Questions typically involve calculating atomic mass, identifying electron configurations, distinguishing between atoms and molecules, and applying valency concepts.

For TET purposes, you must be comfortable with Dalton's atomic theory, Thomson and Rutherford's models, Bohr's model, the concept of shells and subshells, and basic molecular formation rules. The pedagogy angle often asks how to teach abstract atomic concepts using models and analogies—making this topic both content-heavy and pedagogically significant.

Mastering this chapter also builds the base for understanding chemical reactions, bonding, and the periodic table—topics that frequently interconnect in the exam.

Key Concepts

• **Atom**: The smallest particle of an element that retains its chemical properties. Cannot be created or destroyed in a chemical reaction (law of conservation of mass).

• **Molecule**: The smallest particle of an element or compound that can exist independently. Formed when two or more atoms bond together (e.g., H₂, H₂O, CO₂).