IONIC BONDING AND IONIC COMPOUNDS CHAPTER 15

VALENCE ELECTRONS Valence electrons-electrons in the highest occupied energy level Sum of the s and p electrons Group 1 has ____valence electron Group ____ has 2 valence electrons Group 3 has ____ valence electrons 1 2 3

ELECTRON CONFIGURATION FOR CATIONS OCTET RULE-in forming compounds, atoms tend to achieve the electron configuration of a noble gas (set of 8 electrons) Metallic atoms ____ electrons to obey octet rule Most lose between 1 and 3 electrons Metals have a _______ charge POSITIVE LOSE

ELECTRON CONFIGURATION FOR ANIONS Anions GAIN electrons to obey octet rule Most gain between 1 and 3 electrons Nonmetals have a _________ charge NEGATIVE

TRANSITION METALS Charges for transition metal cations vary Do not necessarily obey octet rule Have pseudo-noble gas configuration Examples Ag Fe

15.2 FORMATION OF IONIC BONDS Cations and anions have opposite charges Electrostatic force of attraction called IONIC BOND Electrically neutral compounds formed are called ionic compounds Electrons lost must equal electrons gained

15.2 Properties of Ionic Compounds At room temperature-Crystalline Solids of 3D patterns High melting points-high boiling points Conduct electricity In molten state If water soluble

Metallic Bonding A metallic bond occurs when positive metal ions like Cu+2 or Fe+3 are surrounded by a "sea of electrons" or freely-moving valence electrons.  The valence electrons are not bound to any particular cation, but are free to move throughout the metallic crystal. 

In the picture below, the red circles are metal cations packed in a crystal lattice.  The black dots represent the "sea" of freely moving valence electrons.  

Properties of Metals Metals are good conductors of electricity:  electric current is a movement of free electrons Metals are ductile:  They can be drawn into wires because electrons are mobile. Metals are malleable:  They can be hammered into sheets due to mobility of electrons.

Alloys Alloys are metallic substances composed of two or more elements- at least one of these elements is a metal. Alloys are important because the properties of an alloy are often superior to those of its component elements.

Common alloys are: Stainless steel (composed of iron, chromium, carbon and nickel) Sterling silver    (composed of silver and copper) 14 karat gold    (composed of gold and copper:  Note:  Pure gold is too soft to wear as jewelry!) Brass/bronze  (composed of copper and zinc)