Bellwork
* Read the article on page 141 about hydrogen and write a 2-3 sentence summary.
* Read the article on the handout about helium and write a 2-3 sentence summary.
* Read the article on the handout about helium and write a 2-3 sentence summary.
Anticipation Guide for pages 143-147.
Ions
An ion is an atom that has gained or lost electrons. A positive ion (cation) has lost electrons. Metals form cations. A negative ion (anion) has gained electrons. Atoms gain or lose electrons to reach the octet rule (rule of 8). Stability occurs when all energy levels are full of electrons.
Polyatomic Ions
Sometimes two or more elements form an ion. These are called polyatomic ions. They have a combination of elements, but still need to lose or gain electrons to reach stability. We know they are ions and not neutral compounds, because a charge is shown as a superscript.