Quick Review of Bonding and Naming in Chemistry: Ionic, Covalent, and Metallic Bonds

Unit 7: Bonding and Naming

A Quick Review… • Atoms are electrically neutral • Ions • 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

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

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

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+ • Fe3+ • 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 • 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:

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!!

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:

Quick Review of Bonding and Naming in Chemistry: Ionic, Covalent, and Metallic Bonds