Transcript Ionic Compound


A compound is a pure substance made up of
two or more elements in which the elements
are chemically combined
+
Na
Cl
=
NaCl

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Two types of compounds: Ionic and Molecular
Ionic compounds: composed of positive and
negative ions

An ion is an atom or group of atoms that has
either a positive charge or a negative charge


Ions form when atoms
gain or lose electrons to
become stable
A atom is stable when
the valence shell is full


Sodium loses one electron to become stable
Results in an ion that has a positive charge
x
Na
=

The symbol “+” is written as a superscript to
indicate that the sodium has a charge of 1+
Na+


Chlorine gains one electron to become stable
Results in an ion with a negative charge
=
Cl

The symbol “-” is written as a superscript to
indicate that the chlorine ion has a charge of
1-
Cl-
Both ions have a full valence shell containing the
maximum number of electrons possible
 This new arrangement of valence electrons has less
energy than the previous arrangement and is stable

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When an atom
gives up one or
more electrons
it becomes
positive
Called a cation
“cat-eye-on”

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When an atom
gains one or more
electron it become
negative
Called an anion
(“an-eye-on”)
Ca+ions are
posi+ive
Anions are
negative
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Write the symbol of the element and show
the ion charge as a superscript
Example: 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-

+2
Ca
20p
20n

When an element can
form only one type of
ion, the ion has the
same name as the
element
Eg: Ca2+ = calcium ion


A multivalent element
is an element that can
form an ion in more
than one way
Example: An atom of
copper can form two
different ions: Cu+ or
Cu2+

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The name of an ion of a multivalent element
always contains a Roman numeral that
indicates the ion charge
I=1
II = 2
III = 3
IV = 4
V=5
VI = 6
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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


A nonmetal that has
gained electrons to
become an ion has the
the same name as the
element but with the
ending changed to -ide
Eg: Cl- = chloride ion
nitrogen
oxygen
fluorine
phosphorous
sulfur
chlorine
bromine
iodine








nitride
oxide
fluoride
phosphide
sulfide
chloride
bromide
iodide

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Metal atoms tend to lose electrons
Non-metal atoms tend to gain electrons

The farther the valence electron is from its
positive nucleus, the more easily it is
removed and the more reactive the atom is

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Reactivity generally increases for cations as
you move down the periodic table
Example: potassium is more reactive than
sodium
Sodium
Potassium
Rubidium
Cesium
reactivity increases
Li
Na
K
Li
Na
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Reactivity generally increases
for cations as you move down
the periodic table.
But why?
Electrons that are further away from
the nucleus are more easily lost.
K
Thus atoms with more orbitals will
be more reactive.
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Reactivity generally decreases for anions as you
move down the periodic table
Example: fluorine is more reactive than chlorine
Chlorine
Bromine
Iodine
Astatine
reactivity increases
F
Cl

F

Cl
Reactivity generally decreases for
anions as you move down the
periodic table
But why?
Elements whose valence shell is closer to the
nucleus will gain electrons more readily
because they are closer to the nucleus.
Negative electrons have a stronger attraction
for the positive nucleus when the valence
shell is closer to the nucleus.
A metal atom that has lost electrons (cation)
and a nonmetal atom that has gained electrons
(anion) will have the same number of electrons
as its nearest noble gas.

An metal atom that has lost electrons (cation)
will have the same number of electrons as its
nearest noble gas.

For example, neon is the closest noble gas in the
periodic table to sodium, magnesium and aluminum

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The cations Na+, Mg2+, and Al3+ all have the
same number of electrons as atoms of neon.
This relationship is known as being
isoelectronic (having the same number of
electrons).
+1
Na
11p
12n
Mg +2
12p
12n
Al+3
13p
14n
Ne
10p
10n
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Apply concept to anions
For example, neon is the closest noble gas in the
periodic table to nitrogen, oxygen and fluorine

Prove that these atoms are isoelectronic by drawing the
Bohr diagrams.
Ne
N3-
O2-
F-
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In general, an ionic compound consists of a
metal and nonmetal
It is more accurate to say that ionic
compounds form when atoms of different
elements transfer electrons resulting in ions
of opposite charges.
Thus there is always an electron donor and
acceptor.

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
+
Na
Cl
=
NaCl

During the formation of NaCl, one electron is
transferred from a sodium atom to a chlorine
atom

At room temperature, most are hard, 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
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

When an ionic compound
dissolves in water, the crystal
structure breaks down and
the ions become free to
move.

Solutions of ionic compounds can conduct electricity
Univalent Ionic Compounds are
compounds where the metal ion only
has one possible charge.
1. Name the metal ion first
•
•
The name of the metal ion is the same as the element name
Example: in KBr, the name of the K+ ion is potassium
2. Name the non-metal ion second
•
•
When a non-metal becomes a negative ion, the ending of its
name changes to “ide”
Example: a bromine atom become bromide ion (Br -)
3. The formulas of ionic compounds often contain numbers
called subscripts which can be ignored when
determining the name.
•
Example: Na3P is sodium phosphide
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:
• ZnF2 = zinc fluoride
Multivalent Ionic Compounds are
compounds where the metal ion only
has two or more possible charges.
1. Identify all the possible charges of the ions.
•
•
•
Example: FeO
Fe can be Fe2+ or Fe3+
O is O2-
2. Determine which charge on the multivalent ion is
needed to make the compound neutral
•
Example: Need to use Fe2+ to balance O2-
• 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
1. Identify all the possible charges of the ions.
•
•
•
Example: FeO
Fe can be Fe2+ or Fe3+
O is O2-
2. Determine which charge on the multivalent ion is
needed to make the compound neutral
•
Example: Need to use Fe2+ to balance O2-
3. Name the metal ion indicating the charge in brackets
using Roman numerals
•
1 = I, 2 = II, 3 = III, 4 = IV, 5 = V
4. Name the non-metal ion changing the ending to ‘ide’
•
Example: FeO = Iron (II) oxide
Example Problem 2:
Write the name of the ionic compound MnCl4
1. Identify the ions that form the compound: Mn2+ or Mn4+ and Cl2. Determine the charge of the multivalent ion that would make the
compound neutral.
• Cl4 means there are 4 x Cl- = a total charge of 4• Would need to use Mn4+
3. Name the metal ion indicating the charge using Roman numerals in
brackets and adding the nonmetal –ide.
• Manganese (IV) iodide
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Poly = 2 or more
Atomic = atoms
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A polyatomic ion is a group of atoms,
usually of different elements, that act as
a single ion

Example: one atom of sulphur and four
atoms of oxygen form the polyatomic
ion called sulphate, or SO42-
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Similar polyatomic ions are named using the
suffixes “-ate” or “-ite”
Example: NO3- is nitrate; NO2- is nitrite
Most common polyatomic ions have a
negative charge
However, the ammonium
ion NH4+ has a positive
charge
Name
Formula
ammonium
carbonate
bicarbonate
hydroxide
nitrate
nitrite
permanganate
phosphate
phosphite
sulphate
sulphite
NH4+
CO32HCO3OHNO3NO2MnO4PO43PO33SO42SO32-
Example Problem 3:
Write the name of the ionic compound LiHCO3
1. Name the metal/positive ion:
•
Example: Li+ = lithium
2. Identify the polyatomic ion (use table):
•
Example: HCO3- = hydrogen carbonate
3. Combine the names. Do not change the
polyatomic ending.
•
LiHCO3 = lithium hydrogen carbonate
1. Identify the charge of the ions in the compound
•
•
Example: Calcium chloride
Ca2+ and Cl-
2. Determine the number of positive and negative ions
needed to make the compound neutral
•
Need 2 Cl- to balance 1 Ca2+
3. Write the metal atom first. Use subscript to indicate the
number of ions if it is more than 1. Make sure to use on
the lowest common multiple.
•
•
Calcium chloride = CaCl2
Wrong: Ca2Cl4
Example Problem 4:
Write the chemical formula for Bismuth (V) Phosphide.
• Bi5+ and P3• How many of each do we need to make the compound
neutral?
• Write the chemical formula using subscripts as needed.
1. Identify the charge of the ions in the compound
•
•
Example: Calcium chlorate
Ca2+ and ClO4-
2. Determine the number of positive and negative ions
needed to make the compound neutral
•
Need 2 ClO4- to balance 1 Ca2+
3. Write the metal atom first. If subscripts are needed for
the polyatomic ion, place a bracket around it first. Make
sure to use on the lowest common multiple.
•
Calcium chlorate = Ca(ClO4)2
Example Problem 5:
Write the chemical formula for arsenic (III) acetate.
• As3+ and C2H3O2• How many of each do we need to make the compound
neutral?
• Write the chemical formula using subscripts and
brackets as needed.