Chapter 6: Chemical Names and Formulas Part 1 - Binary Compounds

Binary Compounds Binary Compounds are made of just two elements. There are two types of binary compounds:  Molecular Compounds l Composed of two non-metals (bottom- left corner box of Chart of Ions)  Ionic Compounds l Made by joining metals & nonmetals

Chemical Formulas l Shows the kind and number of atoms in the smallest piece of a substance. l Molecular formula - number and kinds of atoms in a molecule. l CO 2 l C 6 H 12 O 6

Naming Molecular Compounds CH 4 methane BCl 3 boron trichloride CO 2 Carbon dioxide All are formed from two or more nonmetals. Ionic compounds generally involve a metal and nonmetal (NaCl)

Section 6.5 Molecular Compounds l made of just nonmetals l smallest piece is a molecule l Are not held together because of opposite charges (ionic bonds) l can’t use charges to figure out how many of each atom

Molecular Names are easier! l Ionic compounds use charges to determine how many of each. –Have to figure out charges. –Have to figure out numbers. l Molecular compounds: the name tells you the number of atoms. l Use prefixes to tell you the number

Prefixes (Table 6.5, p.159) l 1 = mono- l 2 = di- l 3 = tri- l 4 = tetra- l 5 = penta-

Prefixes l 6 = hexa- l 7 = hepta- l 8 = octa- l 9 = nona- l 10 = deca-

Prefixes l To write the name, write two words: Prefix /namePrefix /name/ -ide

Prefixes l To write the name, write two words: Prefix /namePrefix /name/ -ide l One exception - we don’t write mono if there is only one of the first element. l Use double vowels when writing oxide names? ao & oo = no ; io = yes)

Name These lN2OlN2O l NO 2 l Cl 2 O 7 l CI 4 l SO 3 l BaCl 2 Dinitrogen monoxide Nitrogen dioxide Dichlorine heptoxide Carbon tetraiodide Sulfur trioxide Barium chloride (ionic!)

Write formulas for these l Diphosphorus pentoxide l Tetraiodine nonoxide l Sulfur hexafluoride l Nitrogen trioxide l Carbon tetrahydride l Phosphorus trifluoride l Aluminum chloride P2O5P2O5 I2O9I2O9 SF 6 NO 3 CH 4 PF 3 AlCl 3 (ionic)

Writing Formulas – Binary Ionic Compounds

Ionic Formulas l This formula represents not a molecule, but a formula unit l The smallest whole number ratio of atoms in an ionic compound. l CaCl 2 means there are twice as many chloride ions as Calcium ions. l Ions surround each other so you can’t say which is hooked to which.

Ionic Compounds are held together by Ionic Bonds Equal numbers of Na and Cl ions means a 1:1 ratio and a formula of NaCl. Na 6 Cl Each Na ion is surrounded by 6 Cl ions

Ionic Compounds are held together by Ionic Bonds Equal numbers of Na and Cl ions means a 1:1 ratio and a formula of NaCl. Cl 6 Na Each Cl ion is surrounded by 6 Na ions

Chemical Formulas l Shows the kind and number of atoms in the smallest piece of a substance. l Ionic formula - shows the number and kinds of ions in a formula unit as a whole number ratio: l CaF 2 l Al 2 O 3

Writing Ionic Formulas l The charges on the positive cations and negative anions have to add up to zero. l Balance the charges by adding subscripts. l Subscripts are always positive numbers!!

Charges on ions l For most of the Group A elements, the Periodic Table can tell what kind of monatomic ion they will form from their location l Elements in the same group have the same charge when they form ions:

A 2A 3A5A6A7A Hint: = - 3 Hint: = - 2 Hint: = - 1

What about the others? l Groups 4A and 0 (8A) do not usually form ions: l Group 4A usually forms molecular compounds l Group 0 (8A) rarely forms compounds! l Many transition metals have more than one common ionic charge

A 2A 3A 5A6A7A 0 4A 4A Usually form molecular compounds Group 8A (0) usually do not form compounds at all Transition Metals can have more than one valence.

Naming Group A Metals l Cation- if the charge is always the same (Group A metals), just write the name of the metal.

Helpful to remember In an ionic compound, the net ionic charge is zero (criss-cross method). 2. An -ide ending generally indicates a binary compound. 3. An -ite or -ate ending means there is a polyatomic ion that has oxygen.

Helpful to remember Prefixes generally mean molecular; they show the number of each atom 5. A Roman numeral after the name of a cation shows the ionic charge of the cation (for transition metals). l Use the handout sheet provided by your teacher!

Ionic Formula l This formula represents not a molecule, but a formula unit l The smallest whole number ratio of atoms in an ionic compound. l Ions surround each other so you can’t say which is hooked to which. (p. 140)

Write Formulas for these l Potassium ion l Magnesium ion l Copper (II) ion l Chromium (I) ion l Barium ion l Mercury (II) ion

Name these l Na 1+ l Ca 2+ l Al 3+ l Fe 3+ l Fe 2+ l Pb 2+ l Li 1+

Naming Anions l Anions are always the same charge l Change the element ending to – ide l F 1- Fluorine

Naming Anions l Anions are always the same charge l Change the element ending to – ide l F 1- Fluorin

Naming Anions l Anions are always the same charge l Change the element ending to – ide l F 1- Fluori

Naming Anions l Anions are always the same charge l Change the element ending to – ide l F 1- Fluor

Naming Anions l Anions are always the same charge l Change the element ending to – ide l F 1- Fluori

Naming Anions l Anions are always the same charge l Change the element ending to – ide l F 1- Fluorid

Naming Anions l Anions are always the same charge l Change the element ending to – ide l F 1- Fluoride

Name these l Cl 1- l N 3- l Br 1- l O 2- l Ga 3+

Write these l sulfide ion l iodide ion l phosphide ion l Strontium ion

Naming Binary Ionic Compounds l Binary Compounds - 2 elements. l Ionic - a cation and an anion. l To write the names, just name the two ions. l Easy with Representative elements (which are Group A elements) l NaCl = Na 1 + Cl 1 - = sodium chloride l MgBr 2 = Mg 2+ Br 1 - = magnesium bromide

Naming Binary Ionic Compounds l Write the name of CuO l Need the charge of Cu l O is 2- l copper must be 2+ l Copper (II) oxide l Name CoCl 3 l Cl is 1- and there are three of them = 3- l Co must be 3+ Cobalt (III) chloride

Naming Binary Ionic Compounds l Write the name of Cu 2 S. l Since S is 2-, the Cu 2 must be 2+, so each one is 1+. l copper (I) sulfide l Fe 2 O 3 l Each O is 2- 3 x -2 = -6 l 2 Fe must = 6+, so each is 3+. l iron (III) oxide

Naming Binary Ionic Compounds l Write the names of the following l KCl l Na 3 N l AlN l Ca 3 P 2 l MgO l Na 2 Se Potassium chloride Sodium nitride Aluminum nitride Calcium phosphide Magnesium oxide Sodium selenide

Writing Formulas l The charges have to add up to zero. l Get charges on pieces. l Cations from name on table. l Anions from table or polyatomic. l Balance the charges by adding subscripts. l Put polyatomics in parenthesis.

Writing Formulas l Write the formula for calcium chloride. l Calcium is Ca 2+ l Chloride is Cl 1- l Ca 2+ Cl 1- would have a 1+ charge. l Need another Cl 1- l Ca 2+ Cl 2 1- (use criss-cross method)

Write the formulas for these l Lithium sulfide l Calcium oxide l Aluminum oxide l Magnesium fluoride l Strontium nitride l Potassium sulfide l Calcium phosphide Ca 3 P 2 Li 2 S CaO Al 2 O 3 MgF 2 Sr 3 N 2 K2SK2S

Helpful to remember In an ionic compound, the net ionic charge is zero (criss-cross method). 2. An -ide ending generally indicates a binary compound. 3. An -ite or -ate ending means there is a polyatomic ion that has oxygen and the compound is a ternary compound. (See next section).