Unit 7: Bonding and Naming

A Quick Review… Atoms are electrically neutral Ions Anion Cation Charged particles Anion Negative ion; gain electrons; nonmetals Cation Positive ion; lose electrons; metals

Unit 7 Objectives: Distinguish between ionic, covalent, and metallic bonds Distinguish between ionic and molecular compounds Name ionic and molecular compounds Write formulas for ionic and molecular compounds

Bonds A valence electron from one atom is attracted to another atom’s nucleus Remember… Everything wants a full valence shell Everything wants to have lower Kinetic Energy Can tell the type using the atoms’ electronegativities, or by the type of atoms involved

Ionic Bonds Electrons are donated from one atom to the other Very different electronegativities (difference is >1.7) One atom is MUCH more attracted to electrons than the other Which types of atoms are involved? Metals and non-metals – the metal gives up electrons to the nonmetal

Covalent Bonds Electrons are “shared” by two atoms Similar electronegativity values (difference < 1.7) Closer electronegativities means more equal sharing What types of atoms are involved? 2 nonmetals

Covalent Bonds Atoms always share pairs of electrons Type of Bond Pairs Shared Electrons Shared Single 1 2 Double 4 Triple 3 6

Metallic Bonds What type of atoms? 2 metals Metal cations surrounded by a “sea of electrons”

Determine the Bond Type H-O H-Cl Na-Cl K-Cr Na-Br C-H

Types of Compounds - Ionic Ionic Compounds Contain ionic bonds Electrically Neutral A metal is joined to a non-metal or a polyatomic ion Polyatomic Ion An ion made up of more than one element Covalently Bonded Almost always anions Ex: SO42-

Types of Compounds - Ionic Law of Definite Proportions Small whole number ratios The formula represents a formula unit (NOT a molecule) Formula Units are always simplest ratio (REDUCE!) Ions surround each other so you can’t see which is hooked to which

Types of Compounds - Molecular Contain covalent bonds Non-metals are joined to other non-metals Called molecules Smallest electrically neutral unit that still maintains the properties of the substance Can be one type of atom – O2 Can be a compound – CO2

Distinguishing Between Ionic and Molecular Bond Type Covalent Smallest Piece Formula Unit Molecule Types of Elements Metal-Nonmetal Metal –Polyatomic Ion Nonmetal - Nonmetal State of Matter Solid Solid, liquid, or gas

Chemical Formulas Show the kind and number of each type of atom in a compound For molecules you can also say molecular formula Subscripts are used to tell you if there is more than one of an atom. If there is only one, no subscript. NaCl, BaS CaCl2, C6H12O6

Diatomic Elements Some elements are never found as a single atom If they aren’t bonded to another type of atom, they bond to themselves There are 7: Hydrogen (H2) Nitrogen (N2) Oxygen (O2) Fluorine (F2) Chlorine (Cl2) Bromine (Br2) Iodine (I2)

Oxidation State Remember the trend for the representative elements Transition Metals don’t always have the same oxidation state

Naming Ions Two methods Classical Method – uses root word (in Latin) + suffixes (-ous, -ic). Fe2+ = Ferrous Doesn’t give the true value Doesn’t work for everything Stock System – uses Roman numerals in ( ) to indicate the numerical value. Fe2+ = Iron (II) Much better because it works all the time. We’ll use this one

Roman Numerals No, you don’t get these on the test… Use with transition metals Number Roman Numeral 1 I 2 II 3 III 4 IV 5 V 6 VI 7 VII 8 VIII 9 IX 10 X

Naming Ions - Cations Use the stock system If the charge is always the same (representative elements, Cd, Ag, Zn), just say the name of the element followed by “ion” Example: Ca2+ = calcium ion If it is a metal that varies (transitions, Sn, Pb) say the name of the element, the oxidation state as a Roman Number, followed by “ion” Example: Mb2+ = molybdenum (II) ion

Naming Ions: Exceptions Representative elements that need Roman Numerals Pb Sn Transition metals that no not need a Roman Numeral (bc they always have the same oxidation state) Ag1+ Cd2+ Zn2+

Naming Ions - Cations Write the name of each cation Na1+ Ca2+ Al3+ Li1+ Pb2+ W6+

Writing Formulas- Cations Write the formula for each ion. Potassium Ion Magnesium Ion Copper (II) Ion Silver Ion Mercury (II) Ion Chromium (VI) Ion Barium Ion

Naming Ions - Anions Anions always have the same oxidation state (no need for Roman Numerals) Change the ending of the element to –ide Ex: F = Fluorine F - = Fluoride Ion

Naming Ions - Anions Name the following ions Cl 1- N 3- Br 1- O 2- Ga 3+

Writing Formulas - Anions Write the formula for each ion Sulfide Ion Iodide Ion Phosphide Ion Strontium Ion

Polyatomic Ions Ions containing more than 1 element Almost always anions See list on the back of your Periodic Table or Packet No, You need not memorize them To name them, just check the list and use the name. No change to the ending

Naming Ionic Compounds Binary Compounds only have 2 elements To write the name, just name the 2 ions NaCl - sodium chloride MgBr2 – magnesium bromide

Naming Binary Ionic Compounds A little harder with transition metals… Don’t forget the Roman numerals Ex: CuO Overall, the compound is neutral We know O is 2- Copper must be 2+ Copper (II) Oxide Ex: CoCl3 We know Cl is 1- and there are 3 of them That makes 3- Co must be 3+ Cobalt (III) Chloride

A Few More Examples Cu2S Fe2O3 Sulfur is always: The Copper needs to add up to: There are 2 Copper atoms, so each one is: Name: Fe2O3 Oxygen is always: There are 3 of them, which adds up to: The 2 Iron atoms should add up to: Each Iron is then:

Name some Binary Ionic Compounds KCl Na3N CrN Sc3P2 PbO PbO2 Na2Se

Naming Ternary Ionic Compounds These have polyatomic ions. Name the cation, then name the polyatomic ion Ex: NaNO3 Na = Sodium NO3 = Nitrate Sodium Nitrate The hardest part is remembering to check your list!

Name the Ternary Ionic Compounds LiCN Fe(OH)3 (NH4)2CO3 NiPO4

Writing Formulas for Ionic Compounds Remember, charges add up to ZERO Get the oxidation state of each piece Balance charges out by adding subscripts Polyatomic ions need ( ) if there is more than 1 of it Use the criss-cross method Make the oxidation state of one the subscript of the other. Like finding the least common multiple. Calcium Chloride Ca2+ Cl 1- CaCl2

Write the formulas for these Lithium Sulfide Tin (II) Oxide Tin (IV) Oxide Magnesium Fluoride Copper (II) Sulfate Iron (III) Phosphide Gallium Nitrate Iron (III) Sulfide Ammonium sulfide

Keep in Mind… If you see ( ) it’s telling you the oxidation state of the cation Anions generally end in –ide if it’s an element, and –ate or –ite if it’s a polyatomic ion

Molecular Compounds Made of only Non-metals Electronegativities are similar, they aren’t being held together by opposite charges This means we can’t use the oxidation state to see how many of each atom we have The name will tell you the amount of each atom using prefixes

Prefixes Yes, memorize these!! 1 Mono 2 Di 3 Tri 4 Tetra 5 Penta 6 Hexa 7 Hepta 8 Octa 9 Nona 10 Deca Yes, memorize these!!

Naming Molecular Compounds To write the name: Prefix + first element then Prefix + second element Only one exception this time: if the prefix on the first element is “mono” we don’t write it No double vowels (oa, oo) Rule of thumb: if it sounds weird, you need to drop a vowel

Name the Molecular Compounds N2O NO2 Cl2O7 CBr4 CO BaCl2

Write the Formulas for Molecular Compounds Diphosphorous pentoxide Tetraiodide nonoxide Sulfur hexafluoride Nitrogen trioxide Carbon trtrahydride Phosphorous trifluoride Aluminum chloride

Naming Acids We will save the nomenclature for acids until we start talking about them. For now, here are a couple you should know: Acid Formula Hydrochloric acid HCl Sulfuric Acid H2SO4 Acetic Acid CH3COOH