PeriodicTableSect3.ppt

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Periodic Trends

Sodium chloride (table salt) produced the geometric

pattern in the photograph. Such a pattern can be used to calculate the position of nuclei in a solid. You will learn how properties such as atomic size are related to the location of elements in the periodic table.

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Periodic Trends >

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Trends in Atomic Size

Trends in Atomic Size

What are the trends among the elements for atomic size?

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Periodic Trends > Trends in Atomic Size

The atomic radius is one half of the distance between the nuclei of two atoms of the same element when the atoms are joined.

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Slide 5 of 31 Periodic Trends > Trends in Atomic Size

Group and Periodic Trends in Atomic Size

In general, atomic size

increases from top to bottom within a group and decreases from left to right across a

period.

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Slide 7 of 31 Periodic Trends > Trends in Atomic Size

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Ions

Ions

How do ions form?

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Slide 9 of 31 Periodic Trends > Ions

Positive and negative ions form when

electrons are transferred between atoms.

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Positive and negative ions form when

electrons are transferred between atoms.

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Some compounds are composed of particles called ions.

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

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A cation is an ion with a positive charge.

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An anion is an ion with a negative charge.

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Animation 7

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Trends in Ionization Energy

Trends in Ionization Energy

What are the trends among the elements for first ionization energy, ionic size, and electronegativity?

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Periodic Trends > Trends in Ionization Energy

The energy required to remove an electron from an atom is called ionization energy.

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The energy required to remove the first electron from an atom is called the first ionization energy.

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The energy required to remove an electron from an ion with a 1+ charge is called the second ionization energy.

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Slide 15 of 31 Periodic Trends > Trends in Ionization Energy

Group and Periodic Trends in Ionization Energy

First ionization energy

tends to decrease from top to bottom within a group and increase from left to right

across a period.

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Slide 19 of 31 Periodic Trends > Trends in Ionic Size

Trends in Ionic Size

During reactions between metals and nonmetals, metal atoms tend to lose

electrons, and nonmetal atoms tend to gain electrons. The transfer has a predictable

effect on the size of the ions that form.

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Periodic Trends > Trends in Ionic Size

Cations are always smaller than the atoms from which they form. Anions are always larger than the atoms

from which they form.

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Relative Sizes of Some Atoms and Ions

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Trends in Ionic Size

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Slide 23 of 31 Periodic Trends > 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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Periodic Trends > Trends in Electronegativity

Representative Elements in Groups 1A through 7A

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Summary of Trends

Summary of Trends

What is the underlying cause of periodic trends?

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Periodic Trends > Summary of Trends

The trends that exist among these properties can be

explained by variations in atomic structure.

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Slide 27 of 31 Periodic Trends > Summary of Trends

6.3

Atomic Size Increases

In cr ea se s Decreases D e cr ea se s

Size of cations Shielding

Nuclear Charge Electronegativity Ionization energy Size of anions

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Section Quiz

-or-Continue to: Launch:

Assess students’ understanding of the concepts in Section

Section Assessment

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1. Which of the following sequences is correct for atomic size?

a. Mg > Al > S

b. Li > Na > K

c. F > N > B

d. F > Cl > Br

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6.3 Section Quiz

2. Metals tend to

a. gain electrons to form cations.

b. gain electrons to form anions.

c. lose electrons to form anions.

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6.3 Section Quiz

3. Which of the following is the most electronegative?

a. Cl

b. Se

c. Na

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