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Chapter 6 Inorganic and Organic Compounds: Names and Formulas

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Covalent Compounds and Their Names

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Forming a H2 Molecule

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A covalent bond forms as H atoms move close together to share electrons.

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H2, A Covalent Molecule

In a hydrogen (H2) molecule,

• two hydrogen atoms share electrons to form a covalent single bond

• each H atom acquires two (2) electrons

• each H becomes stable like helium (He)

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Diatomic Elements

• These elements share electrons to form diatomic, covalent molecules.

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What is the name of each of the following diatomic molecules?

H2 ______________________

N2 _______________

Cl2 _______________

O2 _______________

I2 _______________

Learning Check

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What are the names of each of the following diatomic molecules?

H2 hydrogen

N2 nitrogen

Cl2 chlorine

O2 oxygen

I2 iodine

Solution

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Electron-Dot Formulas

Electron-dot formulas show

• the order of bonded atoms in a covalent compound

• the bonding pairs of electrons between atoms

• the unshared (lone) valence electrons

• a central atom with an octet

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Electron-Dot Formulas and Models of Some Covalent Compounds

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Names of Covalent Compounds

Prefixes are used• in the names of covalent compounds• because two nonmetals can form two or

more different compounds

Examples of compounds of N and O:

NO nitrogen oxide

NO2 nitrogen dioxide

N2O dinitrogen oxide

N2O4 dinitrogen tetroxide

N2O5 dinitrogen pentoxide

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Guide to Naming Covalent Compounds

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To name the covalent compound SO3,

STEP 1 Name the first nonmetal by its element name. The element S is sulfur.

STEP 2 Name the second nonmetal by using the first syllable of its element name followed by ide. O is named oxide.

STEP 3 Add prefixes to indicate the number of atoms (subscripts). The subscript 3 of O is shown as the prefix tri.

SO3 → sulfur trioxide The subscript 1(for S) or mono is

understood.

Naming Covalent Compounds

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What is the name of P4S3?

STEP 1 Name the first nonmetal by its element name. P is named phosphorus.

STEP 2 Name the second nonmetal by using the first syllable of its element name followed by ide. S is named sulfide.

STEP 3 Add prefixes to indicate the number of atoms (subscripts). The subscript 4 of P is written as tetra. The subscript 3 of O is written as tri.

P4S3 → tetraphosphorus trisulfide

Naming Covalent Compounds

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Formulas and Names of Some Covalent Compounds

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Select the correct name for each compound.

A. SiCl4 1) silicon chloride

2) tetrasilicon chloride3) silicon tetrachloride

B. P2O5 1) phosphorus oxide

2) phosphorus pentoxide3) diphosphorus pentoxide

C. Cl2O7 1) dichlorine heptoxide

2) dichlorine oxide3) chlorine heptoxide

Learning Check

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Select the correct name for each compound.

A. SiCl4 3) silicon tetrachloride

B. P2O5 3) diphosphorus pentoxide

C. Cl2O7 1) dichlorine heptoxide

Solution

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Write the name of each covalent compound:

CO _____________________

CO2 _____________________

PCl3 _____________________

CCl4 _____________________

N2O _____________________

Learning Check

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Write the name of each covalent compound:

CO carbon monoxide

CO2 carbon dioxide

PCl3 phosphorus trichloride

CCl4 carbon tetrachloride

N2O dinitrogen oxide

Solution

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Example: Write the formula for carbon disulfide.

STEP 1 Write the symbols in the order of the elements in the name. C S

STEP 2 Write any prefixes as subscripts. No prefix for carbon means one(1) C. The prefix di for sulfur means two(2) S.

formula: CS2

Guide to Writing Formulas

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Write the correct formula for each of the following:

A. phosphorus pentachloride

B. dinitrogen trioxide

C. sulfur hexafluoride

Learning Check

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Write the correct formula for each of the following:

A. phosphorus pentachloride

1 P penta = 5 Cl PCl5

B. dinitrogen trioxide

di = 2 N tri = 3 O N2O3

C. sulfur hexafluoride

1 S hexa = 6 F SF6

Solution

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Learning Check

Identify each compound as ionic or covalent and

give its correct name.

A. SO3

B. MnCl2

C. (NH4)3PO4

D. Cu2CO3

E. N2O4

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SolutionIdentify each compound as ionic or covalent and

give its correct name.

A. SO3 covalent; sulfur trioxide

B. MnCl2 ionic; manganese(II) chloride

C. (NH4)3PO3 ionic; ammonium phosphite

D. Cu2CO3 ionic; copper(I) carbonate

E. N2O4 covalent; dinitrogen tetroxide

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Learning Check

Identify each compound as ionic or covalent and

give its correct name.

A. Ca3(PO4)2

B. FeBr3

C. SCl2

D. Cl2O

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Solution

A. Ca3(PO4)2 ionic Ca2+ PO43− calcium

phosphate

B. FeBr3 ionic Fe3+ Br − iron(III) bromide

C. SCl2 covalent 1S 2Cl sulfur dichloride

D. Cl2O covalent 2Cl 1O dichlorine oxide

Basic Chemistry Copyright © 2011 Pearson Education, Inc.