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Section 5.1 Ionic Compounds

Section 5.2 Covalent Compounds

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Section 5.1

Ionic Compounds

• Apply ionic charge to writing formulas for ionic compounds.

• Apply formulas to name ionic compounds.

• Interpret the information in a chemical formula.

Section 5.1

Ionic Compounds

ion: an atom or group of combined atoms that has a charge because of loss or gain of electrons

Section 5.1

Ionic Compounds

binary compound

formula unit

oxidation number

polyatomic ion

hydrate

hygroscopic

deliquescent

anhydrous

The attraction of oppositely charged ions holds atoms in ionic compounds together.

Section 5.1

Binary Ionic Compounds

• Ionic compounds are made up of oppositely charged ions held together strongly in well-organized units.

Section 5.1

Binary Ionic Compounds (cont.)

• A binary compound is a compound that contains only two elements, such as sodium chloride (NaCl).

• In naming a binary ionic compound, the element with the positively charged ion, usually a metal, is named first with the negatively charged ion, usually a nonmetal, named next, modified to end in –ide.

• For example:

oxygen becomes oxide

sulfur becomes sulfide

fluorine becomes fluoride

bromine becomes bromide

•Binary Ionic Compounds (cont.)

Section 5.1

Binary Ionic Compounds (cont.)

• When writing a formula, you add subscripts to the symbols for the ions until the algebraic sum of the ions’ charge is zero.

• If more than one ion of a given element is present in a compound, the subscript indicates how many ions are present.

Section 5.1

Binary Ionic Compounds (cont.)

• The simplest ratio of ions in a compound is called a formula unit.

Section 5.1

Binary Ionic Compounds (cont.)

• Metals tend to lose electrons and become positively charged.

• Nonmetals tend to gain electrons and become negatively charged.

For example:•A sodium ion is written as Na1+ meaning it has one positive charge due to the fact that it loses one electron.

•A chlorine ion is written as Cl1- meaning it has one negative charge due to the fact that it gains one electron.

•When the charges for these two ions are added together, they equal zero. This means a stable compound can be formed by these two elements.

•Binary Ionic Compounds (cont.)

Section 5.1

Binary Ionic Compounds (cont.)

• The charge on the ion is known as the oxidation number of the atom.

Section 5.1

Binary Ionic Compounds (cont.)

• In a polyatomic ion, an ion that has two or more different elements, a group of elements is covalently bonded together when the atoms share electrons.

Section 5.1

Binary Ionic Compounds (cont.)

• In naming a compound with a polyatomic ion, the molecule with the positive charge is named first, followed by the negative ion.

• The ending of the negative polyatomic ion name does not change.

Section 5.1

Binary Ionic Compounds (cont.)

Section 5.1

Compounds of transition elements

• Transition elements can form more than one type of positive ion and have more than one oxidation number.

• To distinguish the names of compounds formed from the different ions of a transition element, scientists use a Roman numeral to indicate the oxidation number of a transition element ion.

Section 5.1

Compounds of transition elements (cont.)

Section 5.1

Compounds of transition elements (cont.)

Section 5.1

Hydrates

• A compound in which there is a specific ratio of water to ionic compound is a hydrate.

• In a hydrate, the water molecules are chemically bonded to the ionic compound.

Section 5.1

Hydrates (cont.)

• A hygroscopic substance is a substance that absorbs water molecules from the air to become a hydrate.

• Compounds that form hydrates often are used as drying agents, also called desiccants, because they absorb so much water from the air when they become hydrated.

Section 5.1

Hydrates (cont.)

• Heating hydrates can result in an anhydrous compound, or a compound in which all the water has been removed.

• To name hydrates, follow the regular name for the compound with the word hydrate, to which a prefix has been added to indicate the number of water molecules present.

Section 5.1

Hydrates (cont.)

Section 5.1

Interpreting Formulas

• A formula summarizes how many atoms of each element are present.

• If more than one formula unit of a compound is present, a coefficient is placed before the formula.

Section 5.1

Section Assessment

The simplest ratio of ions in a compound is called a(n) ___.

A. oxidation unit

B. formula unit

C. binary compound

D. binary ionic compound

Section 5.1

Section Assessment

Which compound is a binary compound?

A. Potassium iodide

B. Lithium copper

C. Iron magneside

D. Sulfur hydrogen

End of Section 5.1

Section 5.2

Covalent Compounds

• Compare the properties of molecular and ionic substances.

• Distinguish among allotropes of an element.

• Apply formulas to name molecular compounds.

Section 5.2

Covalent Compounds

anhydrous: a compound in which all of the water has been removed, usually by heating

Section 5.2

Covalent Compounds

distillation

molecular element

allotrope

organic compound

inorganic compound

hydrocarbon

Covalent bonds hold atoms in covalent compounds together.

Section 5.2

Properties of Covalent Compounds

• The properties of most ionic and covalent compounds are different enough that their differences can be used to classify and separate them from one another.

Section 5.2

Properties of Covalent Compounds (cont.)

• Distillation is the method of separating substances in a mixture by the evaporation of a liquid and subsequent condensation of its vapor.

• Most covalent compounds are not electrolytes because they do not easily form ions.

Section 5.2

• A molecule that forms when atoms of the same element bond together is called a molecular element.

Molecular Elements

Section 5.2

• Seven nonmetal elements are found naturally as diatomic elements, or molecular elements of two identical atoms.

– hydrogen

– nitrogen

– oxygen

– fluorine

Molecular Elements (cont.)

– chlorine

– bromine

– iodine

Section 5.2

• Molecules of a single element that differ in crystalline or molecular structure are called allotropes.

• The properties of allotropes are usually different even though they contain the same element.

Molecular Elements (cont.)

Section 5.2

• Phosphorous has three common allotropes formed from P4 molecules that are joined in different ways.

– Each allotrope of phosphorous has a unique structure and set of properties.

Molecular Elements (cont.)

Section 5.2

• Carbon occurs as several important allotropes with different properties.

– Diamonds are crystals in which the atoms of carbon are held rigidly in place in a three-dimensional network.

– In graphite, carbon atoms are held together closely in flat layers that can slide over each other.

Molecular Elements (cont.)

Section 5.2

• Allotropes of oxygen

– Ozone consists of three atoms of oxygen, occurs naturally, and is harmful to living things.

Molecular Elements (cont.)

Section 5.2

• Substances are either organic or inorganic.

• Compounds that contain carbon, with a few exceptions, are classified as organic compounds.

Formulas and Names of Covalent Compounds

Section 5.2

• Compounds that do not contain carbon are called inorganic compounds.

• If inorganic compounds contain only two nonmetal elements, they are bonded covalently and are referred to as molecular binary compounds.

Formulas and Names of Covalent Compounds (cont.)

Section 5.2

• Naming the compound

– Name of the first nonmental farthest left on the periodic table is listed first, followed by name of second nonmetal with its ending changed to –ide.

– Add a prefix to the name of each element to indicate how many atoms of each element are present.

Formulas and Names of Covalent Compounds (cont.)

Section 5.2

Formulas and Names of Covalent Compounds (cont.)

Section 5.2

• Some scientists use the more common names for certain compounds, such as water, ammonia, and sulfuric acid.

Formulas and Names of Covalent Compounds (cont.)

Section 5.2

Formulas and Names of Covalent Compounds (cont.)

Section 5.2

• The name of even the most complex organic compound is based on the name of a hydrocarbon, an organic compound that contains only the elements hydrogen and carbon.

Formulas and Names of Covalent Compounds (cont.)

• Compounds containing the noble gases helium, neon, and argon have never been found.

Section 5.2

Formulas and Names of Covalent Compounds (cont.)

Section 5.2

Section Assessment

Which of the following is not a hydrocarbon?

A. hexane

B. nonane

C. heptane

D. lexane

Section 5.2

Section Assessment

What is the correct formula for dinitrogen trioxide?

A. N2O3

B. N2O2

C. N3O2

D. N2O

Study Guide 1

Key Concepts

• The position of an element in the periodic table indicates what charge its ions will have.

• Binary ionic compounds are named by first naming the metal element and then the nonmetal element, with its ending changed to –ide. Subscripts are used in formulas to indicate how many atoms of each element are present in the compound.

• Polyatomic ions can combine with ions of opposite charge to form ionic compounds which are named by writing the name of the positive ion first and then the name of the negative ion.

• Most transition elements can form two or more positively charged ions. The oxidation number of the transition element is indicated by a Roman numeral in parentheses.

• Hydrates are ionic compounds bonded to water molecules.

Study Guide 2

Key Concepts

• Covalent compounds generally have low melting points, low water solubility, and little or no ability to act as electrolytes.

• Seven elements occur naturally as diatomic molecules. They are hydrogen, nitrogen, oxygen, fluorine, chlorine, bromine, and iodine.

• Some elements exist in different structural forms called allotropes.

• Binary covalent compounds are named by writing the two elements in the order they are found in the formula, changing the ending of the second element to –ide, and adding Greek prefixes to the element names to indicate how many atoms of each are present.

Chapter Assessment 1

Which compound is not a polyatomic ion?

A. sulfate

B. potassium chloride

C. ammonium

D. hydrogen carbonate

Chapter Assessment 2

What kind of substance absorbs water molecules from the air to become a hydrate?

A. oxidation compound

B. anhydrous compound

C. desiccant

D. hygroscopic substance

Chapter Assessment 3

A formula summarizes how many ___ are present.

A. electrons

B. atoms

C. elements

D. compounds

Chapter Assessment 4

To create an anhydrous compound, what must be added to the hydrates?

A. water

B. air

C. heat

D. light

Chapter Assessment 5

What is the method of separating substances in a mixture by the evaporation of a liquid and subsequent condensation of its vapor?

A. distillation

B. hydration

C. oxidation

D. molecular division

STP 1

How many nonmetal elements are found naturally as molecular elements of two identical atoms?

A. six

B. seven

C. eight

D. twelve

STP 2

Which of the following is not a diatomic element?

A. nitrogen

B. bromine

C. chlorine

D. sulfur

STP 3

Which is an allotrope of oxygen?

A. graphite

B. diamond

C. fullerene

D. ozone

STP 4

Which is the most versatile element in forming allotropes?

A. phosphorous

B. carbon

C. oxygen

STP 5

What is the chemical name for water?

A. dihydroxide oxygen

B. dioxide monohydride

C. dihydrogen monoxide

D. dioxygen hydroxide

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