01 Ionic Compounds

COMPOUNDS

COMPOUNDS

+

=

Na Cl NaCl

A compound is a pure substance made up of A compound is a pure substance made up of

COMPOUNDS

COMPOUNDS

are chemically combined

are chemically combined

two or more elements in which the elements

There are two types

of compounds:

There are two types

of compounds:

COMPOUNDS

COMPOUNDS

ionic

ionic

molecular

An ion is an atom or group of atoms

that has either a positive charge or

a negative charge

An ion is an atom or group of atoms that has either a positive charge or a negative charge

IONIC COMPOUNDS

IONIC COMPOUNDS

An ionic _{compound is formed from} An ionic _{compound is formed from}

one or more positively charged ions

one or more positively charged ions

and one or more negatively charged ions

IONIC COMPO

UNDS

IONIC COMPO

UNDS

Ions form when atoms of different Ions form when atoms of different

elements combine by transferring electrons

elements combine by transferring electrons

from one atom to another

+

=

Na Cl NaCl

For example, this process occurs when atoms of

sodium metal (Na) combine with atoms of chlorine

(Cl) to form sodium chloride (NaCl), or table salt

For example, this process occurs when atoms of sodium metal (Na) combine with atoms of chlorine (Cl) to form sodium chloride (NaCl), or table salt

During the formation of NaCl, one _electron

During the formation of NaCl, one _electron

is transferred from a sodium atom

is transferred from a sodium atom

to a chlorine atom

to a chlorine atom

Each sodium atom loses one electron and

Each sodium atom loses one electron and

IONIC COMPO

UNDS

IONIC COMPO

UNDS

becomes a positively charged ion Na+

becomes a positively charged ion Na+

The symbol “+” is written as a superscript

The symbol “+” is written as a superscript

IONIC COMPO

UNDS

IONIC COMPO

UNDS

to indicate that the sodium has a charge of 1+

to indicate that the sodium has a charge of 1+

Cl

-Each chlorine atom gains one electron

Each chlorine atom gains one electron

IONIC COMPOUNDS

IONIC COMPOUNDS

to become a negatively charged ion Cl

-The symbol “-” is written as a superscript to

The symbol “-” is written as a superscript to

indicate that the chlorine ion has a charge of 1-

indicate that the chlorine ion has a charge of

1-Cl

Notice that both ions have 8 electrons in

Notice that both ions have 8 electrons in

their outermost shell

their outermost shell

Ions often form so that the outer shell is full,

Ions often form so that the outer shell is full,

or contains the maximum number of electrons

or contains the maximum number of electrons

Metal atoms tend to lose _electrons

Metal atoms tend to lose _electrons

Non-metal atoms tend to gain electrons

Non-metal atoms tend to gain electrons

When an atom gives up one or more

When an atom gives up one or more

electrons it becomes _positive

electrons it becomes _positive

called a

cation

(“cat-eye-on”)

When an atom gains one or more

When an atom gains one or more

electrons it becomes _negative

electrons it becomes _negative

called an

anion

(“an-eye-on”)

Ca+ions are posi+ive

Ca

+

ions are posi

+

ive

Anions are negative

The farther the valence electron is from its

The farther the valence electron is from its

positive nucleus, the more easily it is removed

positive nucleus, the more easily it is removed

and the more reactive the atom is

Reactivity generally increases for cations as

you move down the periodic table

ex.) potassium is more reactive than sodium

Reactivity generally increases for cations as you move down the periodic table

ex.) potassium is more reactive than sodium

CATIONS

CATIONS

Lithium

re

ac

tiv

ity

in

cr

ea

se

s

Reactivity generally decreases for anions as

you move down the periodic table

ex.) fluorine is more reactive than chlorine

Reactivity generally decreases for anions as you move down the periodic table

ex.) fluorine is more reactive than chlorine

Fluorine

Fluorine BromineBromine IodineIodine AstatineAstatine

ANIONS

ANIONS

Chlorine

re

ac

tiv

ity

in

cr

ea

se

s

Ionic compounds have the following properties…

Ionic compounds have the following properties…

At room temperature, most are hard,

At room temperature, most are hard,

IONIC COMPOUNDS

IONIC COMPOUNDS

brittle solids that can be crushed

Ionic compounds form crystals that have an

alternating arrangement of positively charged ions and negatively charged ions, so that when

they break their edges are well-defined

Ionic compounds form crystals that have an

alternating arrangement of positively charged ions and negatively charged ions, so that when they break their edges are well-defined

IONIC COMPOUNDS

IONIC COMPOUNDS

In an ionic crystal, every ion is attracted to

every other ion in the crystal. As a result,

ionic crystals have very high melting points

ex.) NaCl melts at 800oC

In an ionic crystal, every ion is attracted to every other ion in the crystal. As a result, ionic crystals have very high melting points

When an ionic compound

dissolves in water, the crystal structure breaks down and the

ions become free to move.

When an ionic compound

dissolves in water, the crystal structure breaks down and the ions become free to move.

Solutions _{of ionic compounds can}

Solutions _{of ionic compounds can}

IONIC COMPOUNDS

IONIC COMPOUNDS

conduct electricity

A cation will react with an anion in order

A cation will react with an anion in order

to acquire a full valence shell

When a cation reacts with an anion the new

arrangement of valence electrons has less

energy than the previous arrangement

When a cation reacts with an anion the new arrangement of valence electrons has less energy than the previous arrangement

For many atoms, this arrangement resembles the

For many atoms, this arrangement resembles the

noble gas that is closest on the periodic table

A metal cation will have the same number of electrons as an atom of the closest noble gas

with a lower atomic number

A metal cation will have the same number of electrons as an atom of the closest noble gas with a lower atomic number

For example, neon is the closest noble

gas in the periodic table to sodium,

magnesium and aluminum

For example, neon is the closest noble gas in the periodic table to sodium,

magnesium and aluminum

The cations Na+, Mg2+, and Al3+ all have the

same number of electrons as atoms of neon

The cations Na+, Mg2+, and Al3+ all have the

same number of electrons as atoms of neon

CATIONS

CATIONS

+2 Ne_Ne

10p

10p

10n

Things to remember:

• Not all atoms will form ions

• Some atoms can form an ion in more

than one way

• Information on the periodic table will

show you the ion charges for each element

Things to remember:

• Not all atoms will form ions

• Some atoms can form an ion in more than one way

• Information on the periodic table will show you the ion charges for each

element

• To write the symbol for an ion, write the

symbol of the element and show the ion

charge as a superscript

• ex.) the symbol of a calcium ion is Ca2+

• When an ion has a charge of 1+ or 1- the symbol has no number in the

superscript, such as Na+ or F

-• To write the symbol for an ion, write the symbol of the element and show the ion charge as a superscript

• ex.) the symbol of a calcium ion is Ca2+

• When an ion has a charge of 1+ or 1- the symbol has no number in the

superscript, such as Na+ or F

When an element can

form only one type of ion,

the ion has the same

name as the element

ex.) Ca2+ = “calcium”

When an element can

form only one type of ion, the ion has the same

name as the element

ex.) Ca2+ = “calcium”

A multivalent element is an element that can form an ion in more

than one way

ex.) An atom of copper can form two different

ions: Cu+ or Cu2+

A multivalent element is an element that can form an ion in more

than one way

ex.) An atom of copper can form two different ions: Cu+ or Cu2+

The name of an ion of a multivalent element always contains a Roman numeral that

indicates the ion charge

The name of an ion of a multivalent element always contains a Roman numeral that

indicates the ion charge

• For example, Cu+ is named copper(I)

(read as “copper one”)

• Cu2+ is named copper(II) (read as

“copper two”)

• Only multivalent metals have Roman

numerals in their names

• For example, Cu+ is named copper(I)

(read as “copper one”)

• Cu2+ is named copper(II) (read as

“copper two”)

• Only multivalent metals have Roman numerals in their names

1. Name the metal ion first

The name of the metal ion is the same as the element name

ex.) in KBr, the name of the K+ ion

is potassium

If the element can form an ion in more than one way, include a

Roman numeral to indicate charge

1. Name the metal ion first

The name of the metal ion is the same as the element name

ex.) in KBr, the name of the K+ ion

is potassium

If the element can form an ion in more than one way, include a

Roman numeral to indicate charge

NAMING IONIC COMPOUNDS

NAMING IONIC COMPOUNDS

2. Name the non-metal ion second

– When a non-metal becomes a negative ion, the ending of its name changes to “ide”

– ex.) a bromine atom (Br)

gains an electron to become

a bromide ion (Br -)

2. Name the non-metal ion second

– When a non-metal becomes a negative ion, the ending of its name changes to “ide”

– ex.) a bromine atom (Br)

gains an electron to become a bromide ion (Br -)

NAMING IONIC COMPOUNDS

NAMING IONIC COMPOUNDS

nitrogen  _nitridenitride

oxygen  oxideoxide

fluorine  _{fluoridefluor}ide

phosphorous  _{phosphidephosph}ide

sulfur  sulfidesulfide

chlorine  _{chloridechlor}ide

bromine  _bromidebromide

3. Name the ionic compound by combining the ion names

The name of KBr is therefore “potassium bromide”

3. Name the ionic compound by combining the ion names

The name of KBr is therefore “potassium bromide”

• The formulas of ionic compounds often contain numbers called

subscripts - ex.) Na₃P

• _{If the metal forms only one type of ion,}

the subscript can be ignored when determining the name

• _{The formulas of ionic compounds} often contain numbers called

subscripts - ex.) Na₃P

• If the metal forms only one type of ion, the subscript can be ignored when

determining the name

• Although ionic compounds are made of charged particles, the compound

itself has no net charge

• All ion charges of an ionic compound

must add up to zero

• Although ionic compounds are made of charged particles, the compound itself has no net charge

• All ion charges of an ionic compound must add up to zero

The positive and negative charges in an

ionic compound must be

equal

The positive and negative charges in an

ionic compound must be

equal

Example Problem 1:

Write the name of the ionic compound ZnF₂ 1. Name the metal ion: Zn forms only one

type of ion (Zn2+), so the name is zinc

2. Name the non-metal ion: The atom is fluorine so the ion is fluoride

3. Combine the names: zinc fluoride

Example Problem 2:

Write the name of the ionic compound PbI₄

• Identify the ions that form the compound: Pb4+ and I

-• Name the metal ion: the ion has a 4+ charge, so the name is lead (IV)

• Name the non-metal ion: the name of the atom is iodine, so the ion is iodide

• Combine the names: lead (IV) iodide

A polyatomic ion is a

group of atoms, usually of different elements, that

act as a single ion

ex.) one atom of sulphur and four atoms of oxygen form the polyatomic ion called sulphate, or SO₄

• Similar polyatomic ions are named using the suffixes “-ate” or “-ite”

• ex.) NO₃- is nitrate; NO

2- is nitrite

• Most common polyatomic ions have a

negative charge

• However, the ammonium

ion NH₄+ has a positive

charge

Name Formula

ammonium NH₄+

carbonate CO₃

2-hydrogen carbonate (bicarbonate)

HCO₃

-hydroxide OH

-nitrate NO₃

-nitrite NO₂

-permanganate MnO₄

-phosphate PO₄

3-phosphite PO₃

3-sulphate SO₄

2-Example Problem 3:

Write the name of the ionic compound LiHCO₃ 1. Name the metal/positive ion:

Li+ = lithium

2. Identify the polyatomic ion (use table): HCO₃- = hydrogen carbonate

3. Combine the names:

lithium hydrogen carbonate