 Determine the number of valence electrons in an atom of a representative element  Explain how the octet rule applies to atoms of metallic and non-metellic elements  Describe how cations and anions form

 Responsible for the chemical properties of atoms and are those in the outer energy level  Valence electrons – the s and p electrons in the outer energy level › The highest occupied energy level  Core electrons – electrons in the energy levels below highest levels

 Atoms in the same column... 1) Have the same outer electron configuration. 2) Have the same valence electrons.  The number of valence electrons are easily determined. It is the group number for a representative element  Group 2A: Be, Mg, Ca, etc. › have 2 valence electrons

 Usually only electrons used in chemical bonds!!! › This means that only valence electrons are shown in electron dot structures  To us older generations – formerly known as Lewis Dot Diagrams

 A way of showing & keeping track of valence electrons.  How to write them?  Write the symbol - it represents the nucleus and inner (core) electrons  Put one dot for each valence electron ( 8 maximum )  They don’t pair up until they have to X

The Electron Dot diagram for Nitrogen l Nitrogen has 5 valence electrons to show l First we write the symbol N l Then add 1 electron at a time to each side l Now they are forced to pair up

 Draw the Electron Dot Diagrams of the following: › Carbon › Argon › Calcium › Aluminum

 Octet › 8 valence electrons › Associated with stability of the noble gases  Exception: Helium › He is stable with 2 valence electrons

 In 1916, Gilbert Lewis used idea of noble gases to explain why atoms form certain kinds of ions and molecules  Octet Rule – in forming compounds, atoms tend to achieve a noble gas configuration – 8 e - in outer level

 Metals LOSE electrons (left side remember!?) to attain a noble gas configuration › When electrons are lost the resulting ion is POSITIVE  Naming – the name of a cation is the same as element › Example: sodium and sodium cation

 Let’s look at configuration of Sodium to explain why metals result in cations: › Na  1s 2 2s 2 2p 6 3s 1 1 valence e - › Na  1s 2 2s 2 2p 6 Noble gas configuration  Same as what element?  Which element is bigger? Why?

 Although names are the same, many chemical differences › Sodium metal reacts explosively with water › Sodium cation is unreactive  Why?

 Metals will have few valence electrons (usually 3 or less) › More than 3 electrons lost is rare but is seen in transition metals  Let’s look at calcium – 2 valence electrons Ca

 Metals will have few valence electrons  Metals will lose their valence electrons Ca

 Metals will have few valence electrons  Metals will lose their valence electrons Ca 2+  No dots are shown for the cation  Name: Calcium ion

 Try Scandium!

 Let’s do Silver, element #47  Predicted configuration is: 1s 2 2s 2 2p 6 3s 2 3p 6 4s 2 3d 10 4p 6 5s 2 4d 9  Actual configuration is: 1s 2 2s 2 2p 6 3s 2 3p 6 4s 2 3d 10 4p 6 5s 1 4d 10 Ag = Ag 1+ (can’t lose any more, charges of 3+ or greater are uncommon)

 Silver cannot lose any more electrons so it does not achieve a true noble gas configuration  Instead it is called “pseudo-noble gas configuration”

 Some transition metals have multiple possible oxidation states (charges). To name them, you add a ROMAN NUMERAL after the name of the element to indicate the charge: ion

 Non-metals gain electrons to attain noble gas configuration › This results in negative charge (anion)  Sulfur – 1s 2 2s 2 2p 6 3s 2 3p 4 › 6 valence electrons  S s 2 2s 2 2p 6 3s 2 3p 6 › Noble gas configuration

 Name of an anion is usually the name of the element but you drop last syllable and add “ide” › Chlorine anions – chloride anions › Oxygen anions – oxygen anions

 Halide ion – ion formed from a halogen element  Non-metals have 5 or more valence electrons › They will GAIN electrons to fill outer shell P 3- Called Phosphide ion SHOW dots!

 All atoms react to try and achieve a noble gas configuration  Noble gases have 2 s and 6 p electrons › 8 valence electrons = stable

 Explain the electrical charge of an ionic compound  Describe three properties of ionic compounds

 Ionic compounds – compounds composed of cations and anions › Usually metal + non-metal  Ionic bond – electrostatic forces that hold ions together in ionic compounds › Opposite charges are attracted to each other › Transfer of electrons

 Metal cation first then non-metal anion with –ide ending › NaCl › LiF  In these ionic compounds there is one sodium atom for every chlorine atom

 Sometimes an ionic compound will have numbers in addition to symbols › Magnesium chloride = MgCl 2

 Chemical formula – shows kinds and numbers of atoms in smallest representative unit of a substance › NaCl  Formula unit – the lowest whole- number ratio of ions in an ionic compound › MgCl 2

 AlBr 3  H 2 O 2  C 6 H 12 O 6

 All the electrons must be accounted for, and each atom will have a noble gas configuration (which is stable). CaP Lets do an example by combining calcium and phosphorus:

CaP

Ca 2+ P

Ionic Bonding Ca 2+ P Ca

Ionic Bonding Ca 2+ P 3- Ca

Ionic Bonding Ca 2+ P 3- Ca P

Ionic Bonding Ca 2+ P 3- Ca 2+ P

Ionic Bonding Ca 2+ P 3- Ca 2+ P Ca

Ionic Bonding Ca 2+ P 3- Ca 2+ P Ca

Ionic Bonding Ca 2+ P 3- Ca 2+ P 3- Ca 2+

Ionic Bonding = Ca 3 P 2 Formula Unit This is a chemical formula, which shows the kinds and numbers of atoms in the smallest representative particle of the substance. For an ionic compound, the smallest representative particle is called a: Formula Unit

 Write the formula for the ionic compound that will form between Ba 2+ and Cl -  Solution: › Balance charge with + and – ions › Write the positive ion first and negative ion second › Cross charges and write number as subscripts

Write the correct formula for the compounds containing the following ions: 1. Na +, S Al 3+, Cl - 3. Mg 2+, N 3-

 Binary ionic compounds: (what is binary?) › Cation first then anion › Cation = name of the element  Ca 2+ = calcium ion › Anion = root + ide  Cl - = chloride › Answer: CaCl 2 is calcium chloride

Complete the names of the following binary compounds: Na 3 N KBr Al 2 O 3 MgS

 Transition metals (as seen before) can have more than one possible charge  Roman numeral indicates charge of ion 1+ or or 3+ Cu +, Cu 2+ Fe 2+, Fe 3+ copper(I) ion iron(II) ion copper (II) ion iron(III) ion

FeCl 3 (Fe 3+ ) iron (III) chloride CuCl (Cu + ) copper (I) chloride SnF 4 (Sn 4+ ) tin (IV) fluoride PbCl 2 (Pb 2+ )lead (II) chloride Fe 2 S 3 (Fe 3+ )iron (III) sulfide

Complete the names of the following binary compounds with variable metal ions: FeBr 2 CuCl SnO 2 Fe 2 O 3 Hg 2 S

 Most ionic compounds are crystalline solids at room temperature › Crystalline – regular repeating arrangement of ions in solid  Ions strongly bonded together  Structure is rigid

 What does it mean to conduct electricity??

 Conducting electricity means allowing charges to move  In a solid (such as salt at room temp) ions are locked in place  Ionic salts are insulators › When melted, ions move › ** Melted ionic compounds conduct electricity

 Model the valence electron in metal atoms  Describe the arrangement of atoms in a metal  Explain the importance of alloys

 Metals are made up of closely packed cations  Metal bonds – consist of attraction of free-floating valence electrons for the positively charged metal ions › Forces of attraction that hold metals together

 Metals hold on to their valence electrons very weakly – they want to give them up!  Metallic bonds look like positive ions floating in a “sea of electrons” › Electrons are free to move through the solid › Metals conduct electricity

 Malleable – hammered into shape (bend)  Ductile – drawn into wires  These explain mobility of valence electrons

- Page 201 1) Ductility2) Malleability Due to the mobility of the valence electrons, metals have: and Notice that the ionic crystal breaks due to ion repulsion!

Force

 Mobile electrons allow atoms to slide by Force

 Strong Repulsion breaks a crystal apart, due to similar ions being next to each other. Force

 If made of one kind of atom, metal atoms are arranged in very compact and orderly patterns  3 arrangements: › Body-centered cubic › Face-centered cubic › Hexagonal close-packed

 Every atom has 8 neighbors except for surface atoms  Examples: › Sodium › Potassium › Iron

 Every atom has 12 neighbors  Examples: › Copper › Silver › Gold › Aluminum

 Every atom has 12 neighbors  Different pattern due to hexagonal shape  Examples: › Magnesium › Zinc › Cadmium

 Metals are used everyday but most are not pure metals  Alloys – mixture of 2 or more elements (at least 1 is a metal)  Made by melting a mixture of the ingredients then cooling it  Example: Brass – alloy of Cu and Zn  Example: Bronze – Cu + Sn

 Properties often better than pure elements › Example: sterling silver is 92.5% Ag and 7.5% Cu – harder and more durable than pure Ag but still soft enough to make jewelry  Steel – important alloy › Corrosion resistant, ductile, hardness, cost

 Page 203 – Table 7.3  Sterling silver – Ag and CU  Cast iron – Fe and C  Stainless steel – Fe, Cr, C, and Ni

 Substitutional alloy – the atoms of the components are about the same size  Interstitial alloy – the atomic sizes are different › Smaller atoms fit into spaces of larger atoms