Ionic Bonding Anions and cations are held together by opposite charges. Ionic compounds are called salts. Simplest ratio of elements in an ionic compound is called the formula unit. The bond is formed through the transfer of electrons. Electrons are transferred to achieve noble gas configuration. Sec. 7.2 & 9.2: Formation and Naming of Ionic Compounds

Ionic Bonding NaCl lose The metal (sodium) tends to lose its one electron from the outer level. nonmetal (chlorine)gain The nonmetal (chlorine) needs to gain one more to fill its outer level, and will accept the one electron that sodium is going to lose.

Ionic Bonding Na + Cl - cation! Note: Remember that NO DOTS are now shown for the cation!

Ionic Bonding 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:

Ionic Bonding CaP

Ionic Bonding 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. Formula Unit For an ionic compound, the smallest representative particle is called a: Formula Unit

Properties of Ionic Compounds Crystalline solidsCrystalline solids - a regular repeating arrangement of ions in the solid Ions are strongly bonded together. –Structure is rigid. –High melting points Coordination number- number of ions of opposite charge surrounding it

Properties of Ionic Compounds

- Page 198 Coordination Numbers: Both the sodium and chlorine have 6 Both the cesium and chlorine have 8 Each titanium has 6, and each oxygen has 3 NaCl CsCl TiO 2

Do they Conduct? Conducting electricity means allowing charges to move. In a solid, the ions are locked in place. Ionic solids are insulators. melted,When melted, the ions can move around. Melted ionic compounds conduct. –NaCl: must get to about 800 ºC. Dissolved in water aqueous solutions)Dissolved in water, they also conduct (free to move in aqueous solutions)

The ions are free to move when they are molten (or in aqueous solution), and thus they are able to conduct the electric current.

Writing Ionic Compound Formulas Example: Barium nitrate (note the 2 word name) 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. Use the criss-cross method to balance subscripts. Not balanced! ( ) 2 Now balanced. = Ba(NO 3 ) 2

Writing Ionic Compound Formulas Example: Ammonium sulfate (note the 2 word name) 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. Use the criss-cross method to balance the subscripts. Not balanced! ( ) 2 Now balanced. = (NH 4 ) 2 SO 4

Writing Ionic Compound Formulas Example: Iron (III) chloride (note the 2 word name) 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. Use the criss-cross method to balance the subscripts. Not balanced! 3 Now balanced. = FeCl 3

Writing Ionic Compound Formulas Example: Aluminum sulfide (note the 2 word name) 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. Use the criss-cross method to balance the subscripts. Not balanced! 23 Now balanced. = Al 2 S 3

Writing Ionic Compound Formulas Example: Magnesium carbonate (note the 2 word name) 1. Write the formulas for the cation and anion, including CHARGES! Mg 2+ CO Check to see if charges are balanced. They are balanced! = MgCO 3

Writing Ionic Compound Formulas Example: Zinc hydroxide (note the 2 word name) 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. Use the criss-cross method to balance the subscripts. Not balanced! ( ) 2 Now balanced. = Zn(OH) 2

Writing Ionic Compound Formulas Example: Aluminum phosphate (note the 2 word name) 1. Write the formulas for the cation and anion, including CHARGES! Al 3+ PO Check to see if charges are balanced. They ARE balanced! = AlPO 4

Naming Ionic Compounds 1. Name the cation first, then anion 2. Monatomic cation = name of the element Ca 2+ = calcium ion 3. Monatomic anion = root + -ide Cl  = chloride CaCl 2 = calcium chloride

Naming Ionic Compounds some metals can form more than one charge (usually the transition metals) use a Roman numeral in their name: PbCl 2 – use the anion to find the charge on the cation (chloride is always 1-) Pb 2+ is the lead (II) cation PbCl 2 = lead (II) chloride (Metals with multiple oxidation states)

Things to look for: 1) If cations have ( ), the number in parenthesis is their charge. 2) If anions end in -ide they are probably off the periodic table (Monoatomic) 3) If anion ends in -ate or –ite, then it is polyatomic

Practice by writing the formula or name as required… Iron (II) Phosphate Stannous Fluoride Potassium Sulfide Ammonium Chromate MgSO 4 FeCl 3