Valence Electrons: ELECTRONS AVAILABLE FOR BONDING

Definition Valence electrons are electrons in the outmost shell (energy level). They are the electrons available for bonding.

Group 1 (alkali metals) have 1 valence electron

Group 2 (alkaline earth metals) have 2 valence electrons

Group 13 elements have 3 valence electrons

Group 14 elements have 4 valence electrons

Group 15 elements have 5 valence electrons

Group 16 elements have 6 valence electrons

Group 17 (halogens) have 7 valence electrons

Group 18 (Noble gases) have 8 valence electrons, except helium, which has only 2

Transition metals (“d” block) have 1 or 2 valence electrons

Lanthanides and actinides (“f” block) have 1 or 2 valence electrons Lanthanides and actinides (“f” block) have 1 or 2 valence electrons

Dot Notations An atom’s valence electrons can be represented by Lewis dot notations. 1 valence e - X 2 valence e - X 3 valence e - X 4 valence e - X 5 valence e - X 6 valence e - X 7 valence e - X 8 valence e - X

Dot Notations – Period 2 Lewis dot notations for the valence electrons of the elements of Period 2. lithium Liberyllium Beboron Bcarbon C nitrogen Noxygen Ofluorine Fneon Ne

Ionic Bonding

Bonds Forces that hold groups of atoms  Forces that hold groups of atoms together and make them function together and make them function as a unit. as a unit.  Ionic bonds – transfer of electrons  Covalent bonds – sharing of electrons

The Octet Rule – Ionic Compounds Ionic compounds form so that each atom, by gaining or losing electrons, has an octet of electrons in its highest occupied energy level. Metals lose electrons to form positively-charged cations Nonmetals gains electrons to form negatively-charged anions

Ionic Bonding: The Formation of Sodium Chloride  Sodium has 1 valence electron Cl: 1s 2 2s 2 2p 6 3s 2 3p 5 Na: 1s 2 2s 2 2p 6 3s 1  Chlorine has 7 valence electrons  An electron transferred gives each an octet

Ionic Bonding: The Formation of Sodium Chloride Cl - 1s 2 2s 2 2p 6 3s 2 3p 6 Na + 1s 2 2s 2 2p 6 This transfer forms ions, each with an octet:

Ionic Bonding: The Formation of Sodium Chloride Cl - Na + The resulting ions come together due to electrostatic attraction (opposites attract): The net charge on the compound must equal zero

Examples of Ionic compounds Mg 2+ Cl - 2 Na + 2 O 2- Magnesium chloride: Magnesium loses two electrons and each chlorine gains one electron Sodium oxide: Each sodium loses one electron and the oxygen gains two electrons Al 3+ 2 S 2- 3 Aluminum sulfide: Each aluminum loses two electrons (six total) and each sulfur gains two electrons (six total)

Sodium Chloride Crystal Lattice Ionic compounds form solid crystals at ordinary temperatures. Ionic compounds organize in a characteristic crystal lattice of alternating positive and negative ions. All salts are ionic compounds and form crystals.

Properties of Ionic Compounds

Ionic Compound Formulas

Ions  Cation: A positive ion  Mg 2+, NH 4 +  Anion: A negative ion  Cl , SO 4 2   Cation: A positive ion  Mg 2+, NH 4 +  Anion: A negative ion  Cl , SO 4 2 

Predicting Ionic Charges Group 1: Lose 1 electron to form 1+ ions H+H+H+H+ Li + Na + K+K+K+K+

Predicting Ionic Charges Group 2: Loses 2 electrons to form 2+ ions Be 2+ Mg 2+ Ca 2+ Sr 2+ Ba 2+

Predicting Ionic Charges Group 13: Loses 3 Loses 3 electrons to form 3+ ions B 3+ Al 3+ Ga 3+

Predicting Ionic Charges Group 14: Lose 4 Lose 4 electrons or gain 4 electrons? Neither! Group 13 elements rarely form ions.

Predicting Ionic Charges Group 15: Gains 3 Gains 3 electrons to form 3- ions N 3- P 3- As 3- Nitride Phosphide Arsenide

Predicting Ionic Charges Group 16: Gains 2 Gains 2 electrons to form 2- ions O 2- S 2- Se 2- Oxide Sulfide Selenide

Predicting Ionic Charges Group 17: Gains 1 Gains 1 electron to form 1- ions F 1- Cl 1- Br 1- Fluoride Chloride Bromide I 1- Iodide

Predicting Ionic Charges Group 18: Stable Noble gases do not form ions! Stable Noble gases do not form ions!

Predicting Ionic Charges Groups : Many transition elements have Many transition elements have more than one possible oxidation state. Iron(II) = Fe 2+ Iron(III) = Fe 3+

Predicting Ionic Charges Groups : Some transition elements Some transition elements have only one possible oxidation state. have only one possible oxidation state. Zinc = Zn 2+ Silver = Ag +

Writing Ionic Compound Formulas Example: Barium nitrate 1. Write the formulas for the cation and anion, including CHARGES! Ba 2+ (NO) Check to see if charges are balanced. 3. Balance charges, if necessary, using subscripts. Use parentheses if you need more than one of a polyatomic ion. balanced! 2

Writing Ionic Compound Formulas Example: Ammonium sulfate 1. Write the formulas for the cation and anion, including CHARGES! NH 4 + SO Check to see if charges are balanced. 3. Balance charges, if necessary, using subscripts. Use parentheses if you need more than one of a polyatomic ion. Not balanced! ( ) 2

Writing Ionic Compound Formulas Example: Iron(III) chloride 1. Write the formulas for the cation and anion, including CHARGES! Fe 3+ Cl - 2. Check to see if charges are balanced. 3. Balance charges, if necessary, using subscripts. Use parentheses if you need more than one of a polyatomic ion. Not balanced! 3

Writing Ionic Compound Formulas Example: Aluminum sulfide 1. Write the formulas for the cation and anion, including CHARGES! Al 3+ S Check to see if charges are balanced. 3. Balance charges, if necessary, using subscripts. Use parentheses if you need more than one of a polyatomic ion. Not balanced! 23

Writing Ionic Compound Formulas Example: Magnesium carbonate 1. Write the formulas for the cation and anion, including CHARGES! Mg 2+ CO Check to see if charges are balanced. They are balanced!

Writing Ionic Compound Formulas Example: Zinc hydroxide 1. Write the formulas for the cation and anion, including CHARGES! Zn 2+ OH - 2. Check to see if charges are balanced. 3. Balance charges, if necessary, using subscripts. Use parentheses if you need more than one of a polyatomic ion. Not balanced! ( ) 2

Writing Ionic Compound Formulas Example: Aluminum phosphate 1. Write the formulas for the cation and anion, including CHARGES! Al 3+ PO Check to see if charges are balanced. They ARE balanced!

Naming Ionic Compounds  Cation first, then anion  Monatomic cation = name of the element  Ca 2+ = calcium ion  Monatomic anion = root + -ide  Cl  = chloride  CaCl 2 = calcium chloride  Cation first, then anion  Monatomic cation = name of the element  Ca 2+ = calcium ion  Monatomic anion = root + -ide  Cl  = chloride  CaCl 2 = calcium chloride

Naming Ionic Compounds (continued)  some metal forms more than one cation  use Roman numeral in name  PbCl 2  Pb 2+ is cation  PbCl 2 = lead(II) chloride  some metal forms more than one cation  use Roman numeral in name  PbCl 2  Pb 2+ is cation  PbCl 2 = lead(II) chloride Metals with multiple oxidation states

Complete These Reviews (They are due before class is over!!!!!!!!!) Monatomic Ions ( zes/MonatomicIons/) zes/MonatomicIons/ Simple Ion Formulas ( Unit2IonicCompoundFormulas.htm)