Presentation on theme: "NOTES: Ionic and Metallic Bonding (CH 7). Valence Electrons: RECALL… ● Valence Electrons: The e- in the highest occupied energy level of an element’s."— Presentation transcript:
Valence Electrons: ● Also, recall…the number of valence electrons for a representative element is equal to the group number of that element Examples: ● Group 1 elements (Na, K, Li, H): 1 valence e-. ● Group 2 elements (Mg, Ca, Be): 2 valence e-. ● Group 17 (7A) elements (Cl, F, Br): 7 valence e-.
Which elements form ionic compounds and which elements form covalent (molecular) compounds?? General Rule of Thumb: metal + nonmetal = IONIC metal + polyatomic anion = IONIC polyatomic cation + anion = IONIC nonmetal + nonmetal(s) = COVALENT
Why are ionic compounds so stable? ● IONIC BONDS: -metal plus a nonmetal -cations plus anions -opposite charges attract ● Examples: Na + and Cl - form NaCl Al 3+ and Br - form AlBr 3
IONIC BONDS: ● Anions and cations have opposite charges ● Ionic compounds are electrically neutral groups of ions joined together by electrostatic forces. (also known as salts) the positive charges of the cations must EQUAL the negative charges of the anions. we can use electron dot structures to predict the ratios in which different cations and anions will combine.
Properties of Ionic Compounds ● must contain an ionic bond ● crystalline solids at room temperature ● ions are arranged in repeating 3-D patterns ● high melting point ● melted or dissolved in water they conduct electricity
Metallic Bonds: ● METALS: made up of closely packed cations surrounded by mobile valence electrons
Metallic Bonds: ● METALLIC BOND = attraction of free- floating (mobile) valence electrons for the positively charged metal ions (sea of electrons around the cations) ● Explains properties of conductivity of electricity, malleability, and ductility
Metallic Properties: ● CONDUCTIVE: can conduct electricity because electrons can flow freely in them ● DUCTILE: can be drawn into wires ● MALLEABLE: can be hammered or forced into different shapes WHY??...the sea of free-flowing electrons insulates the metal cations from each other so they slide easily past one another.
ALLOYS: ● most metallic items we use every day are not pure metals…they are ALLOYS. ● ALLOYS: mixtures composed of 2 or more elements, at least one of which is a metal. ● prepared by melting a mixture of the ingredients together and then cooling