Polyatomic Ions

What is a Polyatomic Ion? = many or several Atomic = atoms So, a polyatomic ion is an ion with more than one atom The charge is on the WHOLE ION not the individual atoms

OH- (O2-H+) (OH)- or OH- Example: Hydroxide Which is really... So the total charge for the whole ion becomes 1- (OH)- But Remember: the negative charge belongs to the entire molecule (the OH) and not just the H. or OH-

There are several polyatomic ions that unfortunately you just have to memorize... (NO3)- 1- (NO2)- 1- (OH)- 1- (HCO3)- 1- (ClO3)- 1- (CO3)2- 2- (SO4)2- 2- (SO3)2- 2- (PO4)3- 3- (PO3)3- 3- (O2)2- 2- (NH4)+ 1+

TERNARY Compounds

Polyatomic Ions can form TERNARY COMPOUNDS Compound = 2 or more different elements Therefore, ternary compounds are compounds composed of 3 different elements

Example #1: Sodium Hydroxide (Metal ion) + (Non-metal polyatomic ion) Example #1: Sodium Hydroxide Sodium Ion = Na+ Hydroxide Ion = (OH)- Na+ (OH)- *Need to balance the charges Na+ : (OH)- (ions) +1 : -1 (charges = balanced) Na1(OH)1 NaOH Like all ionic compounds, sodium hydroxide is neutral

Example #2 Calcium Hydroxide (Metal ion) + (Non-metal polyatomic ion) Example #2 Calcium Hydroxide Calcium Ion = Ca2+ Hydroxide Ion = (OH)- Ca2+ (OH)- *Need to balance the charges Ca2+ : OH- (ions) 2+ : 1- (charges) x1 : x2 (multiply to balance charges) 2+ : 2- (charges are balanced) 1 : 2 (ratio) Ca1(OH)2 CaOH2 Ca(OH)2

What do Ionic Compounds look like?

Ionic Compounds... They tend to be solid at room temperature They exist as crystal lattices Organized in a repeating array Physical properties: Hard Brittle (will shatter with hit with enough force) High melting and boiling points Conduct electricity when dissolved in water

Example #1: Sodium Chloride

Example #2: Sodium Hydroxide

ACTIVITY Look at the products and identify chemical formula of the ionic compounds listed

TOOTHPASTE Sodium Fluoride Ions = Na+ and F- Ionic Compound = NaF

SUNBLOCK Zinc Oxide Ions = Zn2+ and O2- Ionic Compound = ZnO - don’t forget to simplify!

BAKING SODA Sodium Bicarbonate Ions = Na+ and (HCO3)- Ionic Compound = NaHCO3

ANTACIDS (for heartburn) Aluminum Hydroxide Ions = Al3+ and OH- Ionic Compound = Al(OH)3 Magnesium Carbonate Ions = Mg2+ and (CO3)2- Ionic Compound = MgCO3 - don’t forget to simplify!

TUMS (another antacid) Calcium Carbonate Ions = Ca2+ and (CO3)2- Ionic Compound = CaCO3 - don’t forget to simplify

Please work with a partner on the practice questions on your handout Additional homework questions: pg 150 - #9 & 10 pg 151 - 4.1 Review Questions #1-8