Unit 7: Bonding and Naming

A Quick Review…

Atoms are electrically neutralIons

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 compoundsWrite 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 SharedElectrons Shared

Single 1 2

Double 2 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-OH-ClNa-ClK-CrNa-BrC-H

Types of Compounds - Ionic

Ionic Compounds Contain ionic bonds Electrically Neutral A metal is joined to a non-metal or a

polyatomic ionPolyatomic 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 bondsNon-metals are joined to other non-metalsCalled 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 atomIf they aren’t bonded to another type of atom,

they bond to themselvesThere are 7:

1. Hydrogen (H2)

2. Nitrogen (N2)

3. Oxygen (O2)

4. Fluorine (F2)

5. Chlorine (Cl2)

6. Bromine (Br2)

7. Iodine (I2)

Oxidation State

Remember the trend for the representative elements

Transition Metals don’t always have the same oxidation state

Naming Ions

Two methods1. Classical Method – uses root word (in Latin) +

suffixes (-ous, -ic). Fe2+ = Ferrous Doesn’t give the true value Doesn’t work for everything

2. 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 systemIf 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 cationNa1+

Ca2+

Al3+

Fe3+

Li1+

Pb2+

W6+

Writing Formulas- Cations

Write the formula for each ion.Potassium IonMagnesium IonCopper (II) IonSilver IonMercury (II) IonChromium (VI) IonBarium 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 = FluorineF - = Fluoride Ion

Naming Ions - Anions

Name the following ionsCl 1-

N 3-

Br 1-

O 2-

Ga 3+

Writing Formulas - Anions

Write the formula for each ionSulfide IonIodide IonPhosphide IonStrontium Ion

Polyatomic Ions

Ions containing more than 1 elementAlmost always anionsSee 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 elementsTo 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

KClNa3NCrNSc3P2

PbOPbO2

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

LiCNFe(OH)3

(NH4)2CO3

NiPO4

Writing Formulas for Ionic Compounds

Remember, charges add up to ZEROGet the oxidation state of each pieceBalance charges out by adding subscriptsPolyatomic ions need ( ) if there is more than 1 of

itUse 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 SulfideTin (II) OxideTin (IV) OxideMagnesium FluorideCopper (II) SulfateIron (III) PhosphideGallium NitrateIron (III) SulfideAmmonium 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-metalsElectronegativities are similar, they aren’t

being held together by opposite chargesThis means we can’t use the oxidation state

to see how many of each atom we haveThe name will tell you the amount of each

atom using prefixes

Prefixes

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

COBaCl2

Write the Formulas for Molecular Compounds

Diphosphorous pentoxideTetraiodide nonoxideSulfur hexafluorideNitrogen trioxideCarbon trtrahydridePhosphorous trifluorideAluminum 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