Gaining and losing electrons forms ions. Explains ionic composition of compounds between IA or IIA and VIA or VIIA elements. (Illustrate formation of ions of these groups using Lewis structures).

For example:

Count total number of valence electrons

Write a structural formula, connecting atoms by single bonds

Counting each single bond as a pair of electrons, fill in rest of valence electrons to give every atom an octet (except hydrogen).

If not enough electrons, try sharing more than two electrons, to form a double bond or triple bond.

Go through examples:

H₂, Cl₂, H₂O, NH₃, CH₄, CO₂, CO, SO₂, SO₃, NO, O₂, O₃

Note structures below where two or more electron distributions can be written are called Resonance Structures. The actual structure is sort of a hybrid of these as extremes.

Electromagnetic Radiation

What we know as light is just one form of energy known as electromagnetic radiation. So called because as it passes through space it disturbs the electrical and magnetic fields of space. This disturbance gives it the property of a wave, just as the surface of a lake is disturbed.

Demo:

White light through diffraction grating to show rainbow. Laser light showing just one wavelength.

Colors of different ions when activated in flame of a bunsen burner. Explain that this is related to electrons jumping between different energy levels of the atoms.