chapter07_section01_edit.ppt

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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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Trends in Ionic Size

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Trends in Ionic Size

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Trends in Electronegativity

Trends in Electronegativity

 Electronegativity is the ability of an atom of an

element to attract electrons when the atom is in a compound.

 In general, electronegativity values decrease from top

to bottom within a group. For representative

elements, the values tend to increase from left to right across a period.

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As you move from left to right on the

periodic table, what occurs?

1 2 3 4

0% 3%

94%

3%

1.

The atomic

number

decreases

2.

Atomic mass

decreases

3.

Atomic mass

increases

4.

Radioactivity

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Which element has the highest

electronegativity?

1 2 3 4

82%

18%

0% 0%

1.

Magnesium, Mg

2.

Calcium, Ca

3.

Strontium, Sr

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Which of these elements would have

the greatest electronegativity?

1 2 3 4

0% 0% 0%

100%

1.

Nitrogen, N

2.

Oxygen, O

3.

Phosphorus, P

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Which element has the highest

electronegativity?

1 2 3 4

100%

0% 0%

0%

1.

Fluorine, F

2.

Sodium, Na

3.

Sulfur, S

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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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Ions > 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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Ions >

Valence electrons determine an atom´s

1 2 3 4

0% 0% 0%

100%

1. mass

2. Chemical

properties

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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 >

Cesium (Cs) has how many electrons

available for bonding?

1 2 3 4

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Applications of Group 4A Elements

7.1

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Electron dot structures are diagrams that show valence electrons as dots.

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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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Ions > 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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Ions >

Elements found in group 13 or IIIA of the periodic table have how many electrons available for bonding?

1 2 3 4

0% 6% 0%

94%

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Ions >

All elements in group 15 have a valence electron configuration of?

1 2 3 4

0% 0%

33% 67%

1.ns

2

2.ns

2

np

3

3.ns

2

np

5

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Ions >

Which element has four electrons in its

outermost

p

sublevel at ground state?

1 2 3 4

74%

0% 26%

0%

1. Carbon, C

2. Chromium, Cr

3. Sulfur, S

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Ions > 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 >

Radium (Ra) has how many electrons available for bonding?

1 2 3 4

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Ions >

Oxygen has _______ valence electrons and ______ open electron positions available for bonding.

1 2 3 4

0%

40% 60%

0%

1. 2, 2

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Ions >

Which set of atoms has (1) electron for bonding?

1. H and He

2. Li and F

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Ions >

For the following elements give the number of valence electrons and electron dot diagram.

element Valence Electrons Electron Dot diagram

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Formation of Cations

Formation of Cations

How are cations formed?

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Ions > Formation of Cations

An atom’s loss of valence electrons produces a cation, or a positively charged ion.

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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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The electron configuration of the sodium ion is the same as that of a neon atom.

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Using electron dot structures, you can show the ionization more simply.

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The sodium atoms in a sodium-vapor lamp ionize to form sodium cations.

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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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Walnuts are a good dietary

source of

magnesium.

Magnesium ions (Mg2+) aid in

digestive processes.

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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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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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Formation of Anions

Formation of Anions

How are anions formed?

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Ions > 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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The figure shows the symbols of anions

formed by some

elements in Groups 5A, 6A, and 7A.

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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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Both a chloride ion and the argon atom have an octet of electrons in their highest occupied energy levels.

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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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The negatively charged ions in seawater—the

anions—are mostly chloride ions.

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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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Oxygen is in Group 6A.

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Conceptual Problem 7.1

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Practice Problems

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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Section Quiz

-or-Continue to: Launch:

Assess students’ understanding of the concepts in Section

7.1 Section Quiz.

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1. How many valence electrons are there in an atom of oxygen?

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2. Atoms that tend to gain a noble gas

configuration by losing valence electrons are a. metals.

b. nonmetals. c. noble gases.

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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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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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