Naming Ionic and Molecular Compounds

International Union of Pure and Applied Chemistry is responsible for naming compounds. IUPAC

Ionic compounds form when electrons transfer from one atom to another. Ex. In salt, one positive sodium ion is attracted to one negative chloride ion. This neutral unit is called a formula unit (smallest amount of an ionic compound with the composition shown by the chemical formula). A crystal lattice is an organized array of ions. IONIC COMPOUNDS CRYSTAL LATTICE FORMULA UNIT

An atom of sodium has 1 valence electron An atom of chlorine has 7 valence electrons IONIC COMPOUNDS

When the two elements combine, the sodium atom transfers an electron to the chlorine atom. Now, both atoms have full outer energy levels. (stable) IONIC COMPOUNDS THIS IS CALLED IONIC BONDING

Ionic bonds forms between atoms of metals (cations) and non-metals (anions). IONIC COMPOUNDS

1. Name the cation first by using the element’s name (metal) 2. Name the anion second by using the first part of the element’s name and changing the last part to ‘ide.’ (non-metal) Ex. NaCl – sodium chloride BaF 2 – barium fluoride NAMING IONIC COMPOUNDS

All ionic compounds are composed of an equal number of positive and negative charges. To find the formula, given the name… 1. Identify the ions and their charges 2. Determine the total charges needed to balance 3. Use subscripts to write the formula FORMULAS FOR IONIC COMPOUNDS

Ex. Write the formulas for the following ionic compounds… A. magnesium chloride 1. Mg 2+, Cl , MgCl 2 B. calcium nitride 1. Ca2+, N , Ca 3 N 2 Do the remainder of the practice problems on Page 43 (b-e) FORMULAS FOR IONIC COMPOUNDS

Elements with more than one stable electron are called multivalent elements (Ex. Fe 2+ and Fe 3+ ) When naming ionic compounds with multivalent electrons, roman numerals are used to indicate the charge of the ion used. Roman numerals are not used in the formula, because you can already figure out which one is used. COMPOUNDS WITH MULTIVALENT ELECTRONS

Ex. Write the name of the compound that has the formula Cu 3 N (s). 1. Identify the ions that form the compound. Cu? N Positive and negative charges must be equal. Three Cu ions are present in the formula, so each much have a charge of 1+ ( = 3-) 3. Write the name of the compound. Copper (I) nitride Do practice problems on Page 44 COMPOUNDS WITH MULTIVALENT ELECTRONS

Polyatomic ions are ions made up of several non- metallic atoms joined together Ex. Hydroxide is OH -, phosphate is PO 4 3- The two most common suffixes used in naming polyatomic ions are “-ate” and “-ite” Ex. Sulfate is SO 4 2- and sulfite is SO (ate means more atoms) Memorize the polyatomic ions in TABLE A2.5 Pg. 44 There are some common polyatomic ions on Pg. 491 POLYATOMIC IONS

Per ______ ate (1 more oxygen) ClO 4 - perchlorate _________ ate (most common) ClO 3 - chlorate _________ ite (1 less oxygen) ClO 2 - chlorite Hypo ____ ite (2 less oxygen) ClO - hypochlorite POLYATOMIC IONS

Just name the cation and the polyatomic ion. No changes needed. Ex. Ca(OH) 2(s) – calcium hydroxide NAMING COMPOUNDS WITH POLYATOMIC IONS

The rules are the same for writing the formulas for other ionic compounds. Just put the polyatomic ion in brackets if there is more than one. Ex. What is the formula for iron (III) sulfate? 1. Fe 3+, SO Fe 3+ Fe 3+, SO 4 2- SO 4 2- SO Fe 2 (SO 4 ) 3 Do the practice problems on page 46 WRITING FORMULAS FOR COMPOUNDS WITH POLYATOMIC IONS

Water can be trapped in the ionic crystal, not chemically joined, so we use a “dot” to keep the water separate in the formula Ex. Na 2 SO 4 3H 2 O sodium sulfate trihydrate HYDRATED COMPOUNDS

A molecule forms when two or more non-metallic atoms bond together. Ex. CH 3 OH (l) (methanol) and O 2(g) (oxygen gas) In an ion, a formula unit is not an independent unit, it is just one part of a crystal lattice Molecules are independent units made up of fixed numbers of atoms bonded together. MOLECULAR COMPOUNDS

The atoms in a molecule are joined together by covalent bonds that form when atoms share electrons. Each pair of shared electrons forms one covalent bond. Electrons are not transferred from one atom to another as they are in ionic bonds. SHARING ELECTRONS – COVALENT BONDS

Molecular elements are molecules made up of only one type of atom. They can be monatomic (only 1 atom), diatomic (2), or polyatomic (many) Memorize this table MOLECULAR ELEMENTS MonatomicC (s) noble gases all metals DiatomicH 2(g) N 2(g) O 2(g) F 2(g) Cl 2(g) Br 2(l) I 2(s) PolyatomicO 3(g) (ozone) P 4(s) S 8(s)

A binary compound contains 2 elements When naming molecular compounds we use prefixes to indicate how many of each element there is Prefix(not mono) + first element Prefix + second element ending in ‘ide’ MOLECULAR COMPOUNDS THAT DO NOT CONTAIN HYDROGEN PrefixNumber Mono1 Di2 Tri3 Tetra4 Penta5 Hexa6 Hepta7 Octa8 Ennea (nona)9 Deca10 Do the practice problems on Page 49

Many compounds containing hydrogen have simply been given names. See table A2.12 on Page 49 Do Page 50 #1-12 MOLECULAR COMPOUNDS THAT CONTAIN HYDROGEN