Isotopes are atoms of the same element (same number of protons) that have different numbers of neutrons. This gives them identical chemical properties but slightly different physical masses (e.g. Carbon-12 vs Carbon-14).

Core Study Guide

Atomic Structure

The fundamental building blocks of chemical matter.

An atom is the smallest unit of an element that retains its chemical properties. Atoms consist of a dense positive nucleus surrounded by negative electrons.

This unit covers the configuration of subatomic particles (protons, neutrons, electrons), atomic numbers, mass coordinates, and isotopes.

Key Takeaways

•Protons and neutrons reside in the nucleus; electrons occupy quantized energy orbitals.
•The atomic number (Z) equals the proton count, defining the element's identity.
•Isotopes are atoms of the same element with different neutron counts.

Core Concepts & Definitions

1Subatomic Particles

Protons (+1 charge, 1 amu), Neutrons (0 charge, 1 amu), and Electrons (-1 charge, ~0 amu).

•Mass of the atom is concentrated in the nucleus.

•Neutral atoms have equal proton and electron counts.

Quick Revision Notes

•Mass Number = Protons + Neutrons. Atomic Number = Protons.
•Valence electrons are located in the outermost shell and govern chemical bonding.