Chemistry 7.1
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7.1
Ions
Pyrite (FeS2), a common mineral
that emits sparks when struck
against steel, is often mistaken for
gold—hence its nickname, “fool’s
gold.” Pyrite is an example of a
crystalline solid. In this chapter,
you will learn about crystalline
solids composed of ions that are
bonded together. But first you
need to understand how ions form
from neutral atoms.
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Valence Electrons
Valence Electrons
How do you find the number of valence
electrons in an atom of a representative
element?
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Valence Electrons
Valence electrons are the electrons in the
highest occupied energy level of an element’s
atoms.
The number of valence electrons largely
determines the chemical properties of an
element.
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Valence Electrons
To find the number of valence electrons
in an atom of a representative element,
simply look at its group number.
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Ions
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Valence Electrons
Applications of Group 4A Elements
Carbon
Silicon
Germanium
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Ions
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Valence Electrons
Electron dot structures are diagrams that
show valence electrons as dots.
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Ions
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The Octet Rule
The Octet Rule
Atoms of which elements tend to gain
electrons? Atoms of which elements
tend to lose electrons?
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The Octet Rule
Noble gases, such as neon and argon, are
unreactive in chemical reactions. In 1916,
chemist Gilbert Lewis used this fact to explain
why atoms form certain kinds of ions and
molecules.
He called his explanation the octet rule: In
forming compounds, atoms tend to achieve the
electron configuration of a noble gas.
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The Octet Rule
Atoms of metals tend to lose their
valence electrons, leaving a complete
octet in the next-lowest energy level.
Atoms of some non-metals tend to gain
electrons or to share electrons with
another nonmetal to achieve a complete
octet.
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Ions
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Formation of Cations
Formation of Cations
How are cations formed?
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Ions
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Formation of Cations
An atom’s loss of valence electrons
produces a cation, or a positively
charged ion.
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Ions
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Formation of Cations
The most common cations are those produced
by the loss of valence electrons from metal
atoms.
You can represent the electron loss, or
ionization, of the sodium atom by drawing the
complete electron configuration of the atom and
of the ion formed.
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Ions
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Formation of Cations
The electron configuration of the sodium ion is
the same as that of a neon atom.
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Ions
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Formation of Cations
Using electron dot structures, you can show the
ionization more simply.
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Ions
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Formation of Cations
The sodium atoms in a sodium-vapor lamp
ionize to form sodium cations.
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Ions
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Formation of Cations
A magnesium atom attains the electron
configuration of neon by losing both valence
electrons. The loss of valence electrons produces
a magnesium cation with a charge of 2+.
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Ions
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Formation of Cations
Walnuts are a good
dietary source of
magnesium.
Magnesium ions
(Mg2+) aid in
digestive processes.
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Ions
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Formation of Cations
Cations of Group 1A
elements always have a
charge of 1+. Cations of
group 2A elements
always have a charge of
2+.
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Formation of Cations
A copper atom can ionize to form a 1+ cation
(Cu+). By losing its lone 4s electron, copper attains
a pseudo noble-gas electron configuration.
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Ions
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Formation of Anions
Formation of Anions
How are anions formed?
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Formation of Anions
The gain of negatively charged
electrons by a neutral atom produces
an anion.
• An anion is an atom or a group of atoms with
a negative charge.
• The name of an anion typically ends in -ide.
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Formation of Anions
The figure shows the
symbols of anions formed
by some elements in
Groups 5A, 6A, and 7A.
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Formation of Anions
A gain of one electron gives chlorine an octet
and converts a chlorine atom into a chloride ion.
It has the same electron configuration as the
noble gas argon.
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Formation of Anions
Both a chloride ion and the argon atom have an
octet of electrons in their highest occupied
energy levels.
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Ions
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Formation of Anions
In this equation, each dot in the electron dot
structure represents an electron in the valence
shell in the electron configuration diagram.
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Ions
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Formation of Anions
The negatively charged
ions in seawater—the
anions—are mostly
chloride ions.
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Ions
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Formation of Anions
The ions that are produced when atoms of
chlorine and other halogens gain electrons are
called halide ions.
• All halogen atoms have seven valence
electrons.
• All halogen atoms need to gain only one
electron to achieve the electron configuration
of a noble gas.
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Ions
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Formation of Anions
Oxygen is in Group 6A.
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Formation of Anions
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7.1
Conceptual Problem 7.1
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7.1
Conceptual Problem 7.1
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7.1
Conceptual Problem 7.1
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Practice Problems for Conceptual Problem 7.1
Practice Problems For Conceptual Problem 7.1
Problem Solving 7.1 Solve
Problem 1 with the help of an
interactive guided tutorial.
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7.1 Section Quiz.
Assess students’ understanding
of the concepts in Section 7.1.
Continue to:
-or-
Launch:
Section Quiz
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7.1 Section Quiz.
1. How many valence electrons are there in an
atom of oxygen?
a. 2
b. 4
c. 6
d. 8
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7.1 Section Quiz.
2. Atoms that tend to gain a noble gas
configuration by losing valence electrons are
a. metals.
b. nonmetals.
c. noble gases.
d. representative elements.
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7.1 Section Quiz.
3. When a magnesium atom forms a cation, it
does so by
a. losing two electrons.
b. gaining two electrons.
c. losing one electron.
d. gaining one electron.
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7.1 Section Quiz.
4. When a bromine atom forms an anion, it does
so by
a. losing two electrons.
b. gaining two electrons.
c. losing one electron.
d. gaining one electron
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