Chapter 2 The Material World Molecules Chapter 2 The Material World

Bonds

Octet Rule An atom is chemically stable if it has a full outer shell For most elements this means 8 electrons in its outermost shell An atoms that has fewer than 8 electrons tends to combine with another atom or atoms to fill the outermost shell. Exceptions: H, He, Li, Be and B, desire 1 orbital only with 2 electrons in this shell.

Example of an ionic bond: 2+ 2- Mg S

What do atoms do to become chemically stable? Gain electrons (non metals) Lose electrons (metals) Share electrons 2+ 2- Mg S

OR What is a chemical bond? It’s the “Glue” holding atoms together Attraction between opposite charges due to transfer of electrons (ionic bond) Pair of shared electrons (covalent bond) OR

Ionic Bonds Bonds formed by the transfer of valence electrons between atoms → Forming ions

Covalent Bonds Bonds formed by the sharing of valence electrons between atoms

Review: Lewis Dot Notation

Lewis Dot Notation Shows only the electrons in the last orbit since these are the electrons involved in chemical bonding. Examples: Na Br

Lewis Dot Notation – Ion Formation The ion an element is most likely to form is dependent on the number of valence electrons Remember the octet rule: each atom wants to have a complete outer ring

Lewis Dot Notation – Ion Formation Example What is the ion that Aluminum forms? 13 p+ Al 3+ Al Al 10 e- 3+ Dropped to lower level

Element Lewis Dot Diagram Neutral Chemical Ion Hydrogen   Antimony Barium Oxygen

Element Lewis Dot Diagram Neutral Chemical Ion Beryllium   Polonium Cesium Nitrogen