Writing Formulas and Naming Compounds

Writing Formulas and Naming Compounds

SC Standards PS-4.5 Predict the ratio by which the representative elements combine to form binary ionic compounds, and represent that ratio in a chemical formula.

“Perhaps one of you gentlemen would mind telling me just what is outside the window that you find so attractive..?” Image courtesy NearingZero.net

Let’s Review • Warm-up • Distinguish if the compounds on the board are ionic or covalent

Types of Bonds • Ionic • Covalent • Metallic What's the Difference?

Binary Ionic Compounds • Binary compound – compound composed of only two elements KCl MgCl2 AlCl3

Element Charge • Oxidation number – the charge on an ion • Group 1  +1 • Group 2  +2 • Group 16  -2 • Group 17  -1

Writing Chemical Formulas • In order for you to write formulas, you must know the elements charge or oxidation number 0 +1 +2 +3 +4 -3 -2 -1

How do we use an oxidation number? When an element gains or loses an electron it develops a charge… What is sodium’s oxidation number? What is chlorine’s oxidation number?

How do they bond? • A compound is always neutral. • The oxidation numbers always add up to zero. In other words – the amount of positive charge must equal the amount of negative charge Na+ + Cl-NaCl

Transition Metals - most transition metals can form many different ions so a roman numeral is used to show its oxidation number copper (I)  Cu+1 copper (II)  Cu+2

Determining the Formula for an Ionic Compound • Write down the ions of each element • Determine the number of each of the ions it takes to make a compound with no charge • Write down the formula using subscripts to show how many of each ion it took

What is the formula for the compound that forms between magnesium and phosphorous? Mg+2 P-3 3(+2) + 2(-3) = 0 Mg3P2

You Try it!! • Write the formulas for the compounds that form between the following pairs: • Sodium and sulfur • Calcium and bromine • Iron (III) and iodine • Copper (I) and phosphorus

Polyatomic IonsA Group of Atoms that Function as a Single Unit in Compounds and Chemical Reactions ammonium - NH4+1 hydroxide - OH-1 nitrate - NO3-1 carbonate - CO3-2 sulfate - SO4-2 phosphate - PO4-3

What is the formula for the compound between… potassium and sulfate? ammonium and nitride? K+1 SO4-2 K2SO4 2(+1) + (-2) = 0 NH4+1 N-3 3(+1) + (-3) = 0 (NH4)3N

Steps for Naming 1A or 2A metal or Ag, Cd, Zn, Al? Just name it Name the (+) ion (always first) NH4? Just name it Group 3-16 metal? Name with Roman numeral

Name the (-) ion Monoatomic? - name with -ide ending Polyatomic? - Just name it

Practice Naming Compounds… Sodium and Sulfur Na2S Calcium and Bromine CaBr2 Iron(III) and Iodine FeI3 Copper (I) and Phosphorus Cu3P Sodium Sulfide Calcium Bromide Iron (III) Iodide Copper (I) Phosphide

Covalent Bonding Covalent Bonds occur when electrons are being shared Electrons shared equally Electrons shared unequally

Nonpolar Covalent Compounds • e- are shared equally • symmetrical e- density • usually identical atoms

Nonpolar Covalent Compounds Examples: The Magnificent Seven… I2, Br2, Cl2, F2, O2, N2, H2

- + Polar Covalent Compounds • e- are shared unequally • asymmetrical e- density • results in partial charges (poles)

Polar Covalent Compounds Examples: H2O and HCl

Let’s Review • Nonpolar • Polar • Ionic View Bonding Animations.

Writing Formulas and Naming Compounds