ELEMENT RIDDLES Cobalt 1. What you call a cruel and annoying brother _________  Bromine 2. Middle aged men sometimes ________ Cobalt

Ionic Compounds: Names and Formulas

Writing Chemical Formulas Compounds are pure substances made of more than one kind of atom joined together. The atoms are held together with chemical bonds. Compounds come in two basic types: covalent and ionic.

Writing Chemical Formulas Covalent compounds share electrons to form molecules. Example: water

Ionic Compounds Ionic solids exist as a solid in the form of an ionic lattice. The positive ions attract all of the negative ions, and vice versa.

Ionic Compounds In ionic compounds, atoms gain or lose electrons to form ions. Example: NaCl

Polyatomic Ions Covalent and ionic bonds can occur together A molecule can gain or lose electrons to become charged, forming a polyatomic ion. Polyatomic ions form compounds like other ions. Example: Ammonium ion (NH4+) There are many types of polyatomic ions, but they occur in a few basic shapes.

Ion Charge

ELEMENT RIDDLES Seaborgium 1. If you throw a heavy rock into a pond, it will _________  Zinc 2. What caused the “Titanium” (Titanic) to sink was a giant ________ Seaborgium

Naming Monovalent Compounds Each different compound has its own name which tells what elements are in the compound Monovalent elements have only one ion charge e.g. lithium (1+), calcium (2+), aluminum (3+) When naming, there are 2 steps to follow: Write the name of the metallic element first Write the name of the non-metallic element second and change its ending to “-ide”

Some tricky endings: hydrogen – hydride oxygen – oxide phosphorus – phosphide nitrogen – nitride fluorine - fluoride chlorine- chloride bromine- bromide iodine- iodide

Examples: Magnesium + oxygen  magnesium oxide Chlorine + calcium  calcium chloride ZnO  ___zinc oxide Al2S3  ___aluminum sulphide

Writing Monovalent Formulas To write the chemical formula of a compound, do the following: Write the metal and non-metal elements in their ion form (metal always goes first) Rewrite the elements without ion charges, and then crisscross the numbers (omit + and - signs) the numbers are written as subscripts If there is a common factor, reduce the subscripts the number 1 is never written

Examples

Naming Multivalent Compounds Also referred to as transition metals, these only occur after atomic number 20 and have more than one ion charge e.g. lead (2+, 4+), iron (3+, 2+), gold (3+, 1+) When naming these compounds, you must use Roman Numerals to indicate which ion charge has been used I = 1 II = 2 III = 3 IV = 4 V = 5 VI = 6

Naming Multivalent Compounds There are 2 steps to follow: Write the name of the metallic element first, the non-metallic element second and change its ending to “-ide” Work backward from the non-metal ion charge to determine the metal ion charge and write the roman numeral in brackets after the metal  

Naming Multivalent Compounds  Examples AuCl  Gold (I) Chloride Fe2O3  iron (III) oxide MnS2  manganese (IV) sulphide

ELEMENT RIDDLES Tungsten Antimony 1. To dislike riches _______ 2. If you eat lots of blueberries, you might end up with a ________ Tungsten

Writing Multivalent Formulas To write the chemical formula, do the following: Write the metal and non-metal elements in their ion form the Roman numeral tells you which ion charge to use for the metal Rewrite the elements without ion charges, and then crisscross the numbers If there is a common factor, reduce the subscripts

Examples

Naming Polyatomic Compounds Group of atoms with a common name and ion charge. e.g. hydroxide :OH-, sulphate: SO42- It is simple to identify compounds containing polyatomic ions because the formula has 3 or more different elements There are 2 steps to follow: Positive polyatomic ions are written first, like metals Negative polyatomic ions are written second and the name of the ion is not changed

Naming Polyatomic Compounds Examples Calcium + nitrate  calcium nitrate Hydrogen + dichromate  hydrogen dichromate K2SO4  potassium sulphate KMnO4  potassium permanganate

Writing Polyatomic Formulas To write the chemical formula, do the following: Write the metal and non-metal elements in their ion form (polyatomic is always written in brackets) Rewrite the elements without ion charges, and then crisscross the numbers (keep the brackets) If there is a common factor, reduce the subscripts if you have only one of a polyatomic group, omit the brackets

Examples