In this animated and interactive object, learners observe how two, three, or four groups of electrons around the central atom cause the shape of the molecule to be linear, trigonal planar, bent, tetrahedral, or pyramidal. Seven examples and eight interactive questions are provided.

In this interactive and animated object, students distribute the valence electrons in simple covalent molecules with one central atom. Six rules are followed to show the bonding and nonbonding electrons in Lewis dot structures. The process is well illustrated with eight worked examples and two interactive practice problems.

Learners examine the method for calculating the atomic weight of copper from the natural percent composition of each of its two isotopes.

Atomic weights are used to convert the mass of a sample into the number of moles of the element in the sample and vice versa. Four examples are provided for practice.