Sort examples such as oxygen gas, liquid water, table salt, and salt water into atom, element, compound, pure substance, and mixture. Use the particle view to say what kind of particles a sample contains and whether they are all the same.

Read symbols such as Na, Na+, Cl−, Ca2+, and SO42− as neutral atoms or charged ions. Connect cations and anions to an imbalance between protons and electrons without needing to predict charges from the periodic table yet.

Trace how opposite charges attract, like charges repel, and nearby particles can settle into a held arrangement instead of collapsing together. Use this picture to describe a chemical bond as a lasting attraction between particles, not a tiny stick.

Apply the previous explanations in a guided problem.

Translate formulas such as H2O, O2, CO2, NaCl, CaCl2, and Al2(SO4)3 into the particles and numbers they name. Use ion charges to see why ionic formulas combine positive and negative ions in neutral ratios.

Compare separate molecules, ionic lattices, covalent networks, and metals as different ways particles can stay together in space. Decide whether a formula such as H2O, NaCl, SiO2, or Cu represents a single molecule, a formula unit, or a repeating material arrangement.

Apply the previous explanations in a guided problem.

Check your understanding with a short quiz.

Review this chapter with practice based on your mistakes.