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Periodic Trends 6.3

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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.

6.3

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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?

6.3

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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.

6.3

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Periodic Trends >

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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.

6.3

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Periodic Trends > Trends in Atomic Size6.3

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Periodic Trends > Trends in Atomic Size6.3

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Periodic Trends >

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Ions

Ions

How do ions form?

6.3

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Periodic Trends > Ions

Positive and negative ions form when electrons are transferred between atoms.

6.3

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Periodic Trends > Ions

Positive and negative ions form when electrons are transferred between atoms.

6.3

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Periodic Trends > Ions

Some compounds are composed of particles called ions.

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

• A cation is an ion with a positive charge.

• An anion is an ion with a negative charge.

6.3

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Periodic Trends > Ions

Animation 7

Discover the ways that atoms of elements combine to form compounds.

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Periodic Trends >

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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?

6.3

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Periodic Trends > Trends in Ionization Energy

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

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

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

6.3

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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.

6.3

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Periodic Trends > Trends in Ionization Energy6.3

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Periodic Trends > Trends in Ionization Energy6.3

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Periodic Trends > Trends in Ionization Energy6.3

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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.

6.3

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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.

6.3

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Periodic Trends > Trends in Ionic Size

Relative Sizes of Some Atoms and Ions

6.3

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Periodic Trends >

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Periodic Trends > Trends in Ionic Size

Trends in Ionic Size

6.3S

ize

ge

ner

ally

incr

ease

s

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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.

6.3

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Periodic Trends > Trends in Electronegativity

Representative Elements in Groups 1A through 7A

6.3

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Periodic Trends >

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Summary of Trends

Summary of Trends

What is the underlying cause of periodic trends?

6.3

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Periodic Trends > Summary of Trends

The trends that exist among these properties can be explained by variations in atomic structure.

6.3

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Periodic Trends > Summary of Trends6.3

Atomic Size Increases

Incr

ease

s

Decreases

Dec

reas

es

Size of cationsShieldingNuclear ChargeElectronegativityIonization energySize of anionsIonic size Constant

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Periodic Trends >*

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