Chemical Bonds, Names and Formulas

Unit # 6

Big Ideas

OBJECTIVES:– Distinguish between ionic and

molecular compounds.– Distinguish between ionic, covalent

and metallic bonds– Define cation and anion, and relate

them to metal and nonmetal.– Name molecules and compounds

What is a bond? The valence electron of one atom is

attracted to the nucleus of another atom Reasons Why?

– Mutual attraction– To achieve a full valence shell– To have lower Kinetic Energy

Covalent Bonds When a pair of electrons are “shared”

between two atoms This will occur between atoms that have

similar electronegativity values Non-metal bonded to non-metal

Covalent Bonds Single bond – one pair of electrons are

shared (2 electrons) Double bond – two pairs of electrons

are shared (4 electrons) Triple bond – three pairs of electrons

are shared (6 electrons)

Ionic Bonds An unequal sharing of a pair of

electrons between atoms Between a metal and a non-metal We usually say “ the metal will give up

the electron and the non-metal will take the electron

Atoms that have a electronegativity difference higher than 1.7

Metallic Bonds Bonds between 2 metals Both metals will give up electrons and

then share the “sea of electrons”

Determine the bond typeH2OHClNaClKCrKBr

Determine the bond typeH2O covalentHClcovalentNaCl ionicKCrmetallicKBr Ionic

Let’s Review some old concepts to tie this

together

Atoms and ions Atoms are electrically neutral. Same number of protons and electrons. Ions are atoms, or groups of atoms,

with a charge (positive or negative) Different numbers of protons and

electrons. Only electrons can move. Gain or lose electrons.

Anion A negative ion. Has gained electrons. Nonmetals can gain electrons. Charge is written as a superscript on

the right.

F1-Has gained one electron (-ide is new ending= fluoride)

O2- Gained two electrons (oxide)

Cations Positive ions. Formed by losing electrons. More protons than electrons. Metals can lose electrons

K1+ Has lost one electron (no name change for positive ions)

Ca2+ Has lost two electrons

Back to New Material

Now let’s bond the old material to the new material

Two types of Compounds

Ionic and molecular

Ionic Compounds Ionic compounds- from joining

metal and nonmetal - they are electrically neutral

Metal and polyatomic ion

Ionic Bonds

Ionic Compounds This formula represents not a

molecule, but a formula unit The smallest whole number ratio of

atoms in an ionic compound. Ions surround each other so you

can’t say which is hooked to which.

Molecules and Molecular Compounds

Molecular compounds Made of molecules. Made by joining nonmetal atoms

together into molecules. Covalent bonds

Molecules and Molecular Compounds

Molecule- smallest electrically neutral unit, still has properties of the substance

Made from only nonmetals Can be from one element- O2

Can make a compound- CO2

Two Types of Compounds

Smallest piece

Bond Type

State

Types of elements

Formula Unit Molecule

Metal and Nonmetal

Nonmetals

solidSolid, liquid or gas

Ionic Covalent

Ionic Molecular

Chemical Formulas Shows the kind and number of

atoms in the smallest piece of a substance.

Molecular formula- number and kinds of atoms in a molecule.

CO2

C6H12O6

Chemical Formulas More than one atom? –use a

subscript (H2O) There are 7 diatomic elements Hydrogen (H2), Nitrogen (N2),

Oxygen (O2), Fluorine (F2), Chlorine (Cl2), Bromine (Br2), and Iodine (I2)

Remember: “Br I N Cl H O F”

Charges on ions Elements in the same group have

similar properties. Including the charge when they are

ions Remember Group 1 forms +1 ions

2+

1+

3+ 3- 2- 1-

What about the others? Many transition metals have more

than one common ionic charge We use roman numerals in naming

More Big ideas OBJECTIVES:

– Name ions based on their oxidation state

– Define a polyatomic ion, and give the names and formulas of the most common polyatomic ions.

Naming ions Two methods if more than one

charge is possible:

–1. Stock system – uses roman numerals in parenthesis to indicate the numerical value

–2. Classical method – uses root word with suffixes (-ous, -ic)

• Does not give true value

Naming ions We will use the Stock system. Cation- if the charge is always the

same (Group A) just write the name of the metal.

Transition metals can have more than one type of charge.

Indicate the charge with roman numerals in parenthesis

Name these Na1+ Ca2+ Al3+ Fe3+ Fe2+ Pb2+ Li1+

Write Formulas for these Potassium ion Magnesium ion Copper (II) ion Chromium (VI) ion Barium ion Mercury (II) ion

Naming Anions Anions are always the same charge Change the element ending to – ide F1- Fluorine

Naming Anions Anions are always the same charge Change the element ending to – ide F1- Fluorin

Naming Anions Anions are always the same charge Change the element ending to – ide F1- Fluori

Naming Anions Anions are always the same charge Change the element ending to – ide F1- Fluor

Naming Anions Anions are always the same charge Change the element ending to – ide F1- Fluori

Naming Anions Anions are always the same charge Change the element ending to – ide F1- Fluorid

Naming Anions Anions are always the same charge Change the element ending to – ide F1- Fluoride

Name these Cl1- N3- Br1- O2-

Ga3+

Write these Sulfide ion iodide ion phosphide ion Strontium ion

Exceptions: Some of the transition metals have

only one ionic charge:

–Do not use roman numerals for these:

–Silver is always 1+ (Ag1+)

–Cadmium and Zinc are always 2+ (Cd2+ and Zn2+)

Polyatomic ions Groups of atoms that stay together and

have a charge.

Acetate C2H3O21-

Nitrate NO31-

Nitrite NO21-

Hydroxide OH1- and Cyanide CN1- Permanganate MnO4

1-

Polyatomic ions Sulfate SO4

2-

Sulfite SO32-

Carbonate CO32-

Chromate CrO42-

Dichromate Cr2O7

2-

Phosphate PO43-

Phosphite PO33-

Ammonium NH41+

Big Idea

OBJECTIVES:– Apply the rules for naming and writing

formulas for binary ionic and ternary ionic compounds.

Naming Binary Ionic Compounds Binary Compounds - 2 elements. Ionic - a cation and an anion. To write the names, just name the two

ions. Easy with Representative elements

(which are Group A elements) NaCl = Na1+ Cl1- = sodium chloride

MgBr2 = Mg2+ Br1- = magnesium bromide

Naming Binary Ionic Compounds The problem comes with the

transition metals. Need to figure out their charges. The compound must be neutral. same number of + and – charges. Use the anion to determine the

charge on the positive ion.

Naming Binary Ionic Compounds Write the name of CuO Need the charge of Cu O is 2- copper must be 2+ Copper (II) oxide Name CoCl3 Cl is 1- and there are three of them = 3- Co must be 3+ Cobalt (III) chloride

Naming Binary Ionic Compounds Write the name of Cu2S.

Since S is 2-, the Cu2 must be 2+, so each one is 1+.

copper (I) sulfide Fe2O3 Each O is 2- 3 x -2 = -6 2 Fe must = 6+, so each is 3+. iron (III) oxide

Naming Binary Ionic Compounds Write the names of the following KCl Na3N

CrN

Sc3P2

PbO

PbO2

Na2Se

Ternary Ionic Compounds These will have polyatomic ions At least three elements name the ions NaNO3

CaSO4

CuSO3

(NH4)2O

Ternary Ionic Compounds LiCN Fe(OH)3

(NH4)2CO3

NiPO4

Writing Formulas The charges have to add up to

zero. Get charges on pieces. Cations from name on table. Anions from table or polyatomic. Balance the charges by adding

subscripts. Put polyatomics in parenthesis.

Writing Formulas Write the formula for calcium

chloride. Calcium is Ca2+ Chloride is Cl1- Ca2+ Cl1- would have a 1+ charge. Need another Cl1- Ca2+ Cl2

1- (use criss-cross method)

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

Write the formulas for these Ammonium chloride ammonium sulfide barium nitrate

Things to look for If cations have ( ), the number in

parenthesis is their charge. If anions end in -ide they are

probably off the periodic table (Monoatomic)

If anion ends in -ate or -ite it is polyatomic

Section 6.5Molecular Compounds and

Acids OBJECTIVES:

– Apply the rules for naming and writing formulas for binary molecular compounds.

Section 6.5Molecular Compounds and

Acids OBJECTIVES:

– Name and write formulas for common acids.

Molecular compounds made of just nonmetals smallest piece is a molecule can’t be held together because of

opposite charges. can’t use charges to figure out how

many of each atom

Molecular are easier! Ionic compounds use charges to

determine how many of each.–Have to figure out charges.–Have to figure out numbers.

Molecular compounds name tells you the number of atoms.

Uses prefixes to tell you the number

Prefixes (Table 6.5, p.159) 1 = mono- 2 = di- 3 = tri- 4 = tetra- 5 = penta- 6 = hexa- 7 = hepta- 8 = octa-

Prefixes 9 = nona- 10 = deca- To write the name, write two words:

Prefixes 9 = nona- 10 = deca- To write the name, write two words:

Prefix name Prefix name -ide

Prefixes 9 = nona- 10 = deca- To write the name, write two words:

One exception is we don’t write mono- if there is only one of the first element.

Prefix name Prefix name -ide

Prefixes 9 = nona- 10 = deca- To write the name, write two words: One exception is we don’t write mono- if

there is only one of the first element. No double vowels when writing names

(oa oo)

Prefix name Prefix name -ide

Name These N2O

NO2

Cl2O7

CBr4

CO2

BaCl2

Write formulas for these diphosphorus pentoxide tetraiodine nonoxide sulfur hexafluoride nitrogen trioxide carbon tetrahydride phosphorus trifluoride aluminum chloride

Acids

Writing names and Formulas

Acids Compounds that give off hydrogen

ions when dissolved in water. Must have H in them. will always be some H next to an

anion. The anion determines the name.

Naming acids If the anion attached to hydrogen

ends in -ide, put the prefix hydro- and change -ide to -ic acid

HCl - hydrogen ion and chloride ion hydrochloric acid H2S hydrogen ion and sulfide ion hydrosulfuric acid

Naming Acids If the anion has oxygen in it, then it

ends in -ate of -ite change the suffix -ate to -ic acid (use no

prefix) HNO3 Hydrogen and nitrate ions Nitric acid change the suffix -ite to -ous acid HNO2 Hydrogen and nitrite ions Nitrous acid

Name these HF H3P

H2SO4

H2SO3 HCN H2CrO4

Writing Acid Formulas Hydrogen will always be first name will tell you the anion make the charges cancel out. Starts with hydro?- no oxygen, -ide no hydro?, -ate comes from -ic, -ite

comes from -ous

Write formulas for these hydroiodic acid acetic acid carbonic acid phosphorous acid hydrobromic acid

Section 6.6Summary of Naming and

Formula Writing OBJECTIVES:

– Use the flowchart in Figure 6.21 to write the name of a compound when given its chemical formula.

Section 6.6Summary of Naming and

Formula Writing OBJECTIVES:

– Use the flowchart in Figure 6.23 to write a chemical formula when given the name of a compound.

Helpful to remember...1. In an ionic compound, the net ionic

charge is zero (criss-cross method)

2. An -ide ending generally indicates a binary compound

3. An -ite or -ate ending means there is a polyatomic ion that has oxygen

4. Prefixes generally mean molecular; they show the number of each atom

Helpful to remember...5. A Roman numeral after the name of

a cation shows the ionic charge of the cation

Use the handout sheets provided by your teacher!

Summary of Naming and Formula Writing

For naming, follow the flowchart- Fig. 6.21, page 161

For writing formulas, follow the flowchart from Fig. 6.23, p. 162