6. Ions, Isotopes & Reading Atomic Data

Atoms can change in two ways without becoming a different element — and one way that does change the element. The key is knowing which particle changes.

• An ion forms when an atom gains or loses electrons, giving it a charge. Lose an electron → a positive ion (cation); gain an electron → a negative ion (anion).
• An isotope is an atom of the same element (same number of protons) with a different number of neutrons, so it has a different mass. Carbon-12 and Carbon-14 both have 6 protons, but 6 vs. 8 neutrons.
• Change the number of protons, and you have a different element entirely.

Reading atomic data (a GED® skill). A table might list protons, neutrons, electrons, charge, or mass. Use the rules: protons = atomic number, neutrons = mass − atomic number, and a charge tells you electrons were gained or lost.

⚠️ Common misconception: don't confuse the three. Electrons change → ion (charge); neutrons change → isotope (mass); protons change → a different element.

💡 Tip: protons = identity; electrons = charge (ions); neutrons = mass (isotopes).

📚 Sources: OpenStax Chemistry / Chemistry: Atoms First; CK-12 Physical Science; IUPAC Periodic Table.