3Valence ElectronsElectrons that are in the highest occupied energy level of an atom.Mostly determine the chemical properties of an elementValence electrons are usually the only electrons involved in a chemical bond.
4How many valence electrons? Look at the family (or column) it is in on the Periodic Table.Family 1 has 1 electronFamily 2 has 2 electrons…etc.18HHeLiBeBCNOFNeNaMgAlSiPSClArKCaGaGeAsSeBrKrRbSrInSnSbTeIXeCsBaTlPbBiPoAtRnor 2234567Na
5Electron Dot Structure (a.k.a. Lewis Dot Diagram) How do you draw Electron Dot Structures?Write the element symbol.Determine what family it is in.NaThen…put dots around the symbol to represent the valence electrons.Na
7The Octet RuleAtoms tend to gain or lose electrons to achieve the electron configuration of a noble gas (8 e-)Noble gas configuration is 8 electrons in its highest orbital:ns2np6Exception is H and He: only 2 electrons to fill highest orbital
8Cation Cations Definition: A positively charged ion. Has a + sign in word.Cation is an atom that has LOST electrons.Naming:element name (NO change)Add word “ion”
9Examples of Cations Li+1 Lithium ion Na+1 Sodium ion Mg+2 Magnesium ion
10Anion Anions Definition: A negatively charged ion. Letter “A” has negative signAnion is an atom that has GAINED electrons.Naming:Change end of element to ”-ide”Add word “ion”
11Examples of AnionsBr-1Bromide ionO-2Oxide ionCl-1Chloride ion
13Review… Magnesium # of valence electrons 2Gain or lose to achieve octet?lose 2Most stable ion formed:Mg+2Cation or Anion?Positive, so it’s a cation
14Ionic Compounds:Compounds made up of metal cation and nonmetal anions.
15Ionic BondsThe electrostatic force that holds ions together.Positive cations and negative anions attract each other.
16Chemical formula: Li2O NaCl H2SO4 Shows the number and kinds of elements in a compound.Always written with symbols and subscripts.For example:Li2ONaClH2SO4
17Electron Dot Structure and Ionic Bonds Sodium and Iodine
18Naming Ionic Compounds 3 rules:Name of cation stays the same.Change the end of the anion to “-ide”If there is a polyatomic ion, the name doesn’t change. (see chart on page 192)
19Electron Dot Structure and Ionic Bonds Magnesium and Sulfur
20Electron Dot Structure and Ionic Bonds Potassium and Phosphorus
21Electron Dot Structure and Ionic Bonds Aluminum and Oxygen
22Properties of Ionic Compounds Crystalline solids at room temperature.Generally have a high melting point (the elements are highly attracted to each other so they are hard to separate).They conduct an electric current when melted or dissolved.