Lewis Dot and Groups

Groups Identify the number of valence electrons.

• Dots represent the number of valence electrons in an atom.

Octet Rule

Stable atoms (except H & He) require eight valence electrons.

• Atoms that have less than eight tend to react to attain an octet and become more stable.

• This is true for both ionic and covalent bonds.

Ionic Bond Model

Formed by two or more charged atoms

• ​A monatomic bond is formed between a cation and an anion.

  • a metal and a nonmetal

• A polyatomic bond is formed between more than one atom.

  • Metal and nonmetals

Common Polyatomics

These are located on your Periodic Table handout.

Signs and Magnitude

Overall, the molecule has no net (total) charge

• Cations and Anions must be in the lowest ratios that result in the formation of an uncharged molecule.

  • Crisscross method with charges

Signs and Magnitude

• ​A monoatomic bond is formed between a cation and an anion.

  • a metal and a nonmetal

• A polyatomic bond is formed between more than one atom.

  • Metal and nonmetals

Signs and Magnitude

Polyatomic molecules

• The crisscross method requires parentheses or brackets to distinguish between the polyatomic atoms and the quantity of the anion or cation.

​Cations and anions are depicted in brackets, with the valence electrons inside the brackets and the charge above and to the right.

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Dot structures of ionic compounds

​When the ratio of cation to anion is not 1:1, coefficients are used to show the relative numbers of ions.​

Dot structures of ionic compounds