ChemCatalyst How would you make an aluminum ion from an aluminum atom? What type of ion is this? How would you make an oxide ion from an oxygen atom? What type of ion is this?

ChemCatalyst How would you make an aluminum ion from an aluminum atom? What type of ion is this? Al +3 so remove 3 electrons Cation How would you make an oxide ion from an oxygen atom? What type of ion is this? O -2 so add 2 electrons Anion

(Ion)derstand Ions

Ions Atoms are neutral Equal number of protons and electrons Atoms can become charged by gaining or losing an electron Called ions Ions are indicated with a (+) or (-) sign Cations are positive Anions are negative

Why Gain or Lose? Noble gases are unreactive Most stable elements Atoms of elements gain or lose electrons to become more like noble gases

Cations and Anions

Two Types of Cations and Anions Monatomic Ions Ions containing one type of atom Ca 2+ O 2- Polyatomic Ions Ions containing two or more types of atoms NH 4 1+ NO 3 1-

Metals (left side of table) Form cations Lose electrons to get to the noble gases Only works if the charge is +3 or less

Cation Formation Na Na + e-

Naming Metal Cations Metal name + “ion” For transition metals use systematic name Metal name followed by charge written as a Roman numeral in paranthesis + “ion”

Naming Metal Cations Example Write the systematic name for Fe +2 and Fe +3. Fe +2 Iron(II) ion Fe +3 Iron(III) ion

Nonmetals (right side of table) Form anions Gain electrons to get to the noble gases Only works if the charge is -3 or less

Anion Formation Cl - e- Cl

Naming Nonmetal Anions Nonmetal root ending in “ide” + “ion” Example What is the name of the hydrogen anion? Hydride ion What is the name of the nitrogen anion? Nitride ion

Making Salt What is the formula for table salt? What does Na need to do to become like a noble gas? Lose an electron  What does Cl need to do to become like a noble gas?  Gain an electron

Making Salt

But Why?! Ions form so each atom can become like a noble gas When the cation and anion form, we get two charged ions Opposite charges attract Electrostatic force Ionic bond = Ionic compound Metal + nonmetal Left side + right side

Trends in the Table Alkali Metals Form +1 ions Alkaline Earth Metals Form +2 ions Transition Metals Can have multiple charges Halogens Form -1 ions Noble Gases Do not form ions

Chemical Formulas Set of symbols that represent a compound Contains two or more elements chemically combined How does a chemical formula differ from a chemical symbol? Formula is for a substance containing several elements Symbol is for a single element

Symbols vs. Formulas What do Na and O represent? The chemical symbols for sodium and oxygen What does Na 2 O represent? The chemical formula for sodium oxide What does the 2 stand for? 2 sodium ions Why do we put subscripts? To count atoms/balance charges

Naming Formulas Ionic compounds What is the name of AlBr 3 ? No transition metal Step 1: Write the cation name Cation is Al +3 = aluminum ion Step 2: Write the anion name with the ending –ide Anion is Br - = bromide Aluminum bromide

Naming Formulas Ionic compounds What is the name of NiS? Nickel is a transition metal Step 1: Write the cation name Cation is Ni +2 Step 2: Write the charge/ roman numeral of the cation in parenthesis Nickel(II) Step 3: Write the anion name with the ending –ide Anion is S -2 = Sulfide Nickel(II) sulfide

Writing Formulas from names What is the formula for potassium nitride? K = alkali metal = not a transition metal Cation is K + Anion is N -3 K 3 N What is the formula of chromium (III) chloride? Roman numerals = transition metal, so charge is +3 Cation is Cr +3 Anion is Cl - CrCl 3

Naming Molecular Formulas Molecular compounds 2 nonmetals (right side + right side) Uses prefixes Do not write mono for first nonmetal Second nonmetal has -ide ending

Prefixes Number of AtomsPrefix 1Mono 2Di 3Tri 4Tetra 5Penta 6Hexa

Examples What is the name of PCl 3 ? 1 P = phosphorus 3 Cl = trichloride Phosphorus trichloride What is the formula for dihydrogen monoxide? Di = 2 H Mon = 1 O H 2 O