Chapter 4 Compounds and Their Bonds

4.4 Polyatomic Ions

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Polyatomic IonsA polyatomic ion • is a group of atoms. • has an overall ionic charge.

Some examples of polyatomic ions are

NH4+ ammonium OH− hydroxide

NO3−

nitrate NO2−

nitrite

CO32− carbonate PO4

3− phosphateHCO3

− hydrogen carbonate(bicarbonate)

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Some Compounds with Polyatomic Ions

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Some Names of Polyatomic Ions

The names of common polyatomic anions

• end in ate.

NO3− nitrate PO4

3− phosphate

• with one oxygen less end in ite.

NO2− nitrite PO3

3− phosphite

• with hydrogen attached use the prefix hydrogen (or bi).

HCO3− hydrogen carbonate (bicarbonate)

HSO3− hydrogen sulfite (bisulfite)

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Names and Formulas of Common Polyatomic Ions

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Memorize these ions

Naming Compounds with Polyatomic Ions

• The positive ion is named first, followed by the name of the polyatomic ion.

NaNO3 sodium nitrate

K2SO4 potassium sulfate

Fe(HCO3)3 iron(III) bicarbonate

or iron(III) hydrogen carbonate

(NH4)3PO3 ammonium phosphite

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Guide to Naming Compounds with Polyatomic Ions

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Some Compounds with Polyatomic Ions

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Examples

Match each formula with the correct name.

A. MgS 1) magnesium sulfite

MgSO3 2) magnesium sulfate

MgSO4 3) magnesium sulfide

B. Ca(ClO3)2 1) calcium chlorate

CaCl2 2) calcium chlorite

Ca(ClO2)2 3) calcium chloride

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Examples

Name each of the following compounds:

A. Mg(NO3)2

B. Cu(ClO3)2

C. PbO2

D. Fe2(SO4)3

E. Ba3(PO3)2

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Writing Formulas with Polyatomic Ions

The formula of an ionic compound

• containing a polyatomic ion must have a charge balance that equals zero (0).

Na+ and NO3− -> NaNO3

• with two or more polyatomic ions has the polyatomic ions in parentheses.

Mg2+ and 2NO3−

-> Mg(NO3)2

subscript 2 for charge balance

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Examples

Select the correct formula for each.

A. aluminum nitrate

1) AlNO3 2) Al(NO)3 3) Al(NO3)3

B. copper(II) nitrate

1) CuNO3 2) Cu(NO3)2 3) Cu2(NO3)

C. iron(III) hydroxide

1) FeOH 2) Fe3OH 3) Fe(OH)3

D. tin(IV) hydroxide

1) Sn(OH)4 2) Sn(OH)2 3) Sn4(OH)

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ExamplesWrite the correct formula for each.

A. potassium bromateB. calcium carbonateC. sodium phosphateD. iron(II) nitrite

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Flowchart for Naming Ionic Compounds

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ExamplesName the following compounds:

A. Ca3(PO4)2

B. FeBr3

C. Al2S3

D. NaHCO3

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ExamplesWrite the formulas for the following:

A. iron(II) hydroxide

B. aluminum carbonate

C. copper(II) bromide

D. lithium phosphate

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Chapter 4 Compounds and Their Bonds

4.5Covalent Compounds

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Copyright © 2009 by Pearson Education, Inc.

Covalent BondsCovalent bonds form

• when atoms share electrons to complete octets.

• between two nonmetal atoms.

• between nonmetal atoms from Groups 4A (14), 5A (15), 6A (16), and 7A (17).

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Hydrogen Molecule

A hydrogen molecule

• is stable with 2 electrons (helium).

• has a shared pair of electrons.

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Forming Octets in Molecules

In a fluorine, F2,, molecule, each F atom

• shares 1 electron.• attains an octet.

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Carbon Forms 4 Covalent Bonds

In a CH4 (methane) molecule,

• 1 C atom shares electrons with 4 H atoms to attain an octet.

• each H atom shares 1 electron to become stable, like helium.

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Multiple Bonds

In a nitrogen molecule, N2,

• each N atom shares 3 electrons.• each N attains an octet.• the bond is a multiple bond called a triple

bond.• the name is the same as the element.

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Naming Covalent Compounds

In the names of covalent compounds, prefixes are used to indicate the number of atoms (subscript) of each element. (mono is usually omitted)

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Guide to Naming Covalent Compounds

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Naming Covalent Compounds

What is the name of SO3?

1. The first nonmetal is S sulfur.

2. The second nonmetal is O, named oxide.

3. The subscript 3 of O is shown as the prefix tri.

SO3 -> sulfur trioxide

The subscript 1 (for S) or mono is understood.

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Naming Covalent Compounds

Name P4S3.

1. The first nonmetal, P, is phosphorus.

2. The second nonmetal, S, is sulfide.

3. The subscript 4 of P is shown as tetra.

The subscript 3 of O is shown as tri.

P4S3 -> tetraphosphorus trisulfide

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Formulas and Names of Some Covalent Compounds

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ExamplesSelect the correct name for each compound.

A. SiCl4 1) silicon chloride2) tetrasilicon chloride3) silicon tetrachloride

B. P2O5 1) phosphorus oxide2) phosphorus pentoxide3) diphosphorus pentoxide

C. Cl2O7 1) dichlorine heptoxide2) dichlorine oxide3) chlorine heptoxide

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Examples

Write the name of each covalent compound.

CO _____________________

CO2 _____________________

PCl3 _____________________

CCl4 _____________________

N2O _____________________

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Guide to Writing Formulas for Covalent Compounds

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Example: Writing Formulas for Covalent Compounds

Write the formula for carbon disulfide.

STEP 1: Elements are C and S

STEP 2: No prefix for carbon means 1 C

Prefix di = 2

Formula: CS2

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Examples

Write the correct formula for each of the following:

A. phosphorus pentachloride

B. dinitrogen trioxide

C. sulfur hexafluoride

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ExamplesIdentify each compound as ionic or covalent, and

give itscorrect name.

A. SO3

B. BaCl2

C. (NH4)3PO3

D. Cu2CO3

E. N2O4

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ExamplesDetermine if each is ionic (I) or covalent (C ), and

write the formula.

A. calcium nitrate

B. boron trifluoride

C. aluminum carbonate

D. dinitrogen tetroxide

E. copper(I) phosphate34

ExamplesIdentify each compound as ionic or covalent and

give itscorrect name.

A. Ca3(PO4)2

B. FeBr3

C. SCl2

D. Cl2O

E. N2

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