Section 2.3—Chemical Formulas We need to be able to read the formulas for chemicals in the antacids!

Reminders from Section 2.2 Your Chemistry Chart has lists of: Common polyatomic ions Multivalent metals Covalent prefixes Use your periodic table to determine the charges of common elements when they form ions

Binary Ionic compounds

Definitions Ionic bond- bond formed by attraction between + and - ions Binary Ionic Compound- compound containing two elements—one metal and one non-metal + Cation - Anion Ionic Compound

Metals & Non-Metals Ionic Bonds are between metals & non-metals H He Li Be B C N O F Ne Na Mg Al Si P S Cl Ar K Ca Sc Ti V Cr Mn Fe Co Ni Cu Zn Ga Ge As Se Br Kr Rb Sr Y Zr Nb Mo Tc Ru Rh Pd Ag Cd In Sn Sb Te I Xe Cs Ba Lu Hf Ta W Re Os Ir Pt Au Hg Tl Pb Bi Po At Rn Fr Ra Lr Rf Db Sg Bh Hs Mt Uun Uuu Uub Uut Metals Metalloids Non-metals

Identifying & Naming Binary Ionic These compounds: End in “-ide” (except “hydroxide and cyanide”) Do NOT contain covalent prefixes To write these formulas: Write the symbol & charge of the first element (the metal, cation) Write the symbol & charge of the second element (the non-metal, anion) Add more of the cations and/or anions to have a neutral compound Use subscripts to show how many of each type of ion is there.

Example #1 Sodium chloride

Example #1 Na+1 Cation Sodium chloride Anion Cl-1 NaCl

NaCl Example #1 Sodium chloride Cation Anion Na+1 Na+1Cl-1 +1 + -1 = 0 The compound is neutral…no subscripts are needed. Cl-1 NaCl

Example #2 Calcium bromide

Example #2 Ca+2 Cation Calcium bromide Anion Br-1

CaBr2 Example #2 Calcium bromide Cation Anion Ca+2 Ca+2Br-1 +2 + -1 = +1 Anion Ca+2Br-1Br-1 Br-1 +2 + -1 + -1 = 0 CaBr2 The subscript “2” is used to show that 2 anions are needed.

Write the following chemical formulas Let’s Practice Cesium chloride Potassium oxide Calcium sulfide Lithium nitride Example: Write the following chemical formulas

Write the following chemical formulas Let’s Practice Cesium chloride Potassium oxide Calcium sulfide Lithium nitride CsCl K2O CaS Li3N Example: Write the following chemical formulas

Polyatomic Ionic Compounds

Definition Polyatomic Ion- more than one atom that together have a charge Polyatomic Ionic Compound- compound containing at least one polyatomic ion + Cation - Polyatomic Anion Polyatomic Ionic Compound

Identifying & Naming Polyatomic Ionic These compounds: Do not end with “-ide” (except hydroxide & cyanide) Do not use covalent prefixes To write these formulas: Write the symbol & charge of the cation & anion Add additional cations or anions to have a neutral compound Use subscripts to show the number of ions When using subscripts with a polyatomic ion, you must put the polyatomic ion in parenthesis.

Example #3 Sodium carbonate

Example #3 Na+1 Cation Sodium carbonate Polyatomic Anion CO3-2

Na2CO3 Example #3 Sodium carbonate Cation Polyatomic Anion Na+1 +1 + -2 = -1 Polyatomic Anion Na+Na+CO32- +1 + 1 + -2 = 0 CO3-2 Na2CO3 The subscript “2” is used to show that 2 cations are needed.

Example #4 Magnesium nitrate

Example #4 Mg+2 Cation Magnesium nitrate Polyatomic Anion NO3-1

Mg(NO3)2 Example #4 Magnesium nitrate Cation Polyatomic Anion Mg+2 +2 + -1 = 1 Magnesium nitrate Mg+2NO3- NO3- Polyatomic Anion +2 + -1 + -1 = 0 NO3-1 The subscript “2” is used to show that 2 anions are needed. Mg(NO3)2 Use parenthesis when adding subscripts to polyatomic ions

Write the following chemical formulas Let’s Practice Sodium nitrate Calcium chlorate Potassium sulfite Calcium hydroxide Example: Write the following chemical formulas

Write the following chemical formulas Let’s Practice Sodium nitrate Calcium chlorate Potassium sulfite Calcium hydroxide NaNO3 Ca(ClO3)2 K2SO3 Ca(OH)2 Example: Write the following chemical formulas

Multivalent Metals

Definition Multivalent Metal- metal that has more than one possibility for cationic charge

Identifying & Naming Multivalent Metals These compounds: Will have roman numerals To write these formulas: Same as binary ionic or polyatomic ionic. The roman numerals tell the charge of the metal (cation)

Example #5 Iron (III) oxide

Example #5 Fe+3 Cation Iron (III) oxide Anion O-2

Fe2O3 Example #5 Iron (III) oxide Cation Anion Fe+3 Fe+3O2- +3 + -2 = -1 Iron (III) oxide Fe+3Fe+3O2-O2- Anion +3 + 3 + -2 + -2 + -2 = 0 O-2 The subscript “2” and “3” are used to show the numbers of atoms needed. Fe2O3

Example #6 Copper (II) nitrate

Example #6 Cu+2 Cation Copper (II) nitrate Polyatomic Anion NO3-1

Cu(NO3)2 Example #6 Copper (II) nitrate Cation Polyatomic Anion Cu+2 +2 + -1 = 1 Copper (II) nitrate Cu+2NO3-NO3- Polyatomic Anion +2 + -1 + -1 = 0 NO3-1 Use parenthesis when adding subscripts to a polyatomic ion Cu(NO3)2

Write the following chemical formulas Let’s Practice Iron (II) nitrate Copper (I) chloride Lead (IV) hydroxide Tin (II) oxide Example: Write the following chemical formulas

Write the following chemical formulas Let’s Practice Iron (II) nitrate Copper (I) chloride Lead (IV) hydroxide Tin (II) oxide Fe(NO3)2 CuCl Pb(OH)4 SnO Example: Write the following chemical formulas

Binary Covalent Compounds

Definition Covalent bond atoms share electrons Binary Covalent Compound compound made from two non-metals that share electrons Non metal Non metal Covalent compound

Identifying & Naming Binary Covalent These compounds: Use covalent prefixes To write these formulas: Write the symbols of the first and second element Use the covalent prefixes (assume the first element is “1” if there’s no prefix) as the subscripts to show number of atoms. Atoms do not form charges when bonding covalently…you DO NOT need to worry about charges with this type!

Dinitrogen Tetraoxide Example #7 Dinitrogen Tetraoxide

Dinitrogen Tetraoxide Example #7 “Di-” = 2 N Dinitrogen Tetraoxide O “Tetra-” = 4 N2O4

Example #8 Silicon dioxide

Silicon dioxide SiO2 Example #8 Si O “Mono-” is not written for the first element Si Silicon dioxide O “Di-” = 2 SiO2

CAUTION!!! “di” and “bi” do not mean the same thing! di- bi- Stands for “2” in covalent compounds Means there’s a hydrogen in the polyatomic anion Carbon dioxide = CO2 Sodium biphosphate = Na2HPO4

Write the following chemical formulas Let’s Practice Carbon monoxide Nitrogen dioxide Diphosphorus pentaoxide Example: Write the following chemical formulas

Write the following chemical formulas Let’s Practice Carbon monoxide Nitrogen dioxide Diphosphorus pentaoxide CO NO2 P2O5 Example: Write the following chemical formulas

Nomenclature Summary Writing Chemical Formulas Does not contain covalent prefixes Does contain covalent prefixes = Binary Covalent compound Ends with “-ide” (except hydroxide & cyanide) = Binary Ionic All others = Polyatomic Ionic

Write the following chemical formulas Mixed Practice Magnesium hydroxide Copper (II) nitrate Iron (III) oxide Nitrogen dioxide Sodium bicarbonate Example: Write the following chemical formulas

Write the following chemical formulas Mixed Practice Magnesium hydroxide Copper (II) nitrate Iron (III) oxide Nitrogen dioxide Sodium bicarbonate Mg(OH)2 Cu(NO3)2 Fe2O3 NO2 NaHCO3 Example: Write the following chemical formulas