Ionic Compound A compound made up of one or more positive metal ions (cations) and one or more negative non-metal ions (anions) Most ionic compounds have: High melting points are hard and brittle Form electrolytes (conduct electricity) when dissolved in water to form solutions

Formation of Sodium Chloride

Chemical Formula of an Ionic Compound Step 1: Write the symbols of the elements, with the metal on the left-hand side and the non-metal on the right-hand side. Mg Cl Step 2: Add the ionic charge of each ion above the symbol +2 -1

Step 3: Determine the number of ions required to bring the charge to zero. 1(+2) + 2(-1) = 0 Mg O Step 4: Write the chemical formula using the (red) coefficients in front of each bracket as subscripts Mg1Cl2 Note: Do not write the subscript “1” The chemical formula for magnesium chloride is MgCl2

Crisscross Method Step 1: Write the symbols of the elements and their ionic charges Mg 2+ Cl- Step 2: Crisscross the numbers of the ionic charges so that they now become subscripts MgCl2

Considering Multiple Ionic Charges Write the chemical name of CuBr2. Note that copper could have either of two ionic charges (+1 or +2). Each bromide ion has a charge of -1, so the total charge of bromide ions is 2(-1). The ionic charge of copper in this compound is +2 Roman numerals are included ONLY if the metal has more than one ionic charge. The name of CuBr2 is copper (II) bromide

MOLECULAR COMPOUNDS Nitrogen dioxide, NO2 , is the gas responsible for the reddish-brown colour of smog Inhaling nitrous oxide, N2O , helps dental patients relax

Most of the chemicals we encounter are molecular compounds, including: Acetylsalicylic acid, or Aspirin sugar water

Soft Drinks Sugar C12H22O11 Carbon Dioxide CO2 Water H2O

Living Organisms Make thousands of different kinds of molecular compounds Sugars, fats, and proteins are all molecular compounds Some of them are very large, containing thousands of atoms in a single molecule

Molecular Compounds The majority of all known compounds are molecular Molecules consist of two or more non-metal atoms joined by a covalent bond A COVALENT BOND forms when atoms share electrons The chemical formula gives the exact numbers of atoms in each molecule Diatomic molecules consist of only two atoms of either the same or different elements

Ionic Bond vs Covalent Bond An Ionic bond is the simultaneous strong attraction of positive ions and negative ions A covalent bond results from the sharing of outer electrons between non-metal atoms

Naming Molecular Compounds Prefixes indicate how many atoms of each element are present (for example, dinitrogen pentoxide, N2O5) If there is only one atom of the first element, the prefix “mono” is omitted The name of the last element ends in “ide.” Prefix Number of Atoms Mon(o)- 1 Di- 2 Tri- 3 Tetra- 4 Penta- 5

Writing Formulas of Molecular Compounds Sulfur dioxide SO2 Prefixes in the name become the subscripts in the formula

Hotdogs contain many chemical additives Sodium nitrite Preservative and colour enhancer Sodium phosphate Binding agent Sodium erythrobate Preservative

Nitrites are not all bad news ... Research suggests that sodium nitrite may help protect heart tissue after a heart attack or heart transplant Nitrites and nitrates occur naturally in soil and are important plant nutrients

Polyatomic Ions Phosphate Ion A polyatomic ion is an ion that consists of a stable group of several atoms acting together as a single charged particle. The ionic charge of a polyatomic ion is shared over the entire ion rather than being on just one atom 3- Phosphate Ion

Formulas and Charges of Common Polyatomic Ions Name of Polyatomic Ion Ion Formula Ionic Charge Nitrate ion NO3- - 1 Nitrite ion NO2- Hydroxide OH- Carbonate CO32- - 2 Sulfate SO42- Phosphate PO43- - 3 Ammonium NH4+ + 1

Naming Compounds involving Polyatomic Ions Write the name of the compound Fe(NO3)3 Step 1: Write the name of the metal and check whether it has more than one possible ionic charge. Iron has two possible charges (+2 and +3) Step 2: Determine the ionic charge of the metal. Fe(NO3)3 x + 3(-1) = 0 x = + 3 Step 3: Write the name of the compound with the Roman numeral if necessary. The name of Fe(NO3)3 is iron (III) nitrate.

Writing Formulas for Compounds Containing Polyatomic Ions What is the chemical formula of copper (II) nitrate? Step 1: Write the symbol of each ion, with its charge. Cu2+ (NO3)- Step 2: Crisscross the numbers of the ionic charges so that they become subscripts. Cu2+ (NO3)- Step 3: Write any necessary subscripts after the brackets around each ion. The formula of copper (II) nitrate is Cu(NO3)2

What is the most common ending for the name of .... A) a polyatomic anion? “ –ate” (nitrate, chlorate, sulfate, phosphate) B) an anion made up of only one element? “ –ide” (nitride, chloride, sulfide, phosphide)