Chemical Bonding Chapter 13 Ionic Bonds Section 2

Reminder… Valence Electrons effect the bonding of atoms The happy magic number is… 8

Electron Transfer Atoms with 1-3 electrons will lose e- to become stable. Metal donor stable – an atom with a full valence shell Atoms with 5-7 electrons will gain e- to become stable. Nonmetal receiver

Charge of An Atom IF… # of protons = # of electrons the atom becomes an ION ion – is an atom or group of atoms that has become electrically charged.

Charge of An Atom If # protons > # electrons = positive charge atom loses electron CATION If # protons < # electrons = negative charge atom gains electron ANION

Ions CATION (+) ANION (-)    

Forming an Ionic Bond Sodium donates an e- and becomes positively charged. Na+ Chlorine gains an e- and becomes negatively charged. Cl- Positive sodium and negative chlorine attract each other. Sodium chloride (table salt) is formed. NaCl ionic bond - attraction between two oppositely charged ions. Compounds are electrically neutral. Atoms form compounds for this reason and will join with other atoms that will give each one a full valence shell.

Polyatomic Ions Ions that are made of more than one atom are examples of polyatomic ions. Poly means many. Each polyatomic ion has an overall negative or positive charge. Ex: carbonate (CO32- ) can combine with calcium (Ca2+) to form calcium carbonate (CaCO3 ).

Naming Ionic Compounds The name of the positive ion comes first. If the negative ion is an element, the end of the element name is changed to -ide. If the negative ion is polyatomic, its name is unchanged.

Properties of Ionic Compounds Crystal Shape High Melting Points -- ex: Salt 801ºC Electrical Conductivity A solid ionic compound does not conduct electricity very well b/c the ions are tightly bound to each other. When ionic compounds dissolve in water, the ions separate and the solution will conduct electricity. In an ionic compound, every ion is attracted to ions near it that have an opposite charge.