IIIIII III. Periodic Trends (p. 140 - 154) Ch. 5 - The Periodic Table

I II III

III. Periodic Trends(p. 140 - 154)

Ch. 5 - The Periodic Table

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0 5 10 15 20Atomic Number

Ato

mic

Ra

diu

s (

pm

)

A. Periodic Law

When elements are arranged in order of

increasing atomic #, elements with similar

properties appear at regular intervals.

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Ato

mic

Ra

diu

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Atomic Number

B. Chemical Reactivity

Families Similar valence e- within a group result in

similar chemical properties

B. Chemical Reactivity

Alkali MetalsAlkaline Earth MetalsTransition MetalsHalogensNoble Gases

Atomic Radius size of atom: ½ distance

between nuclei of identicalatoms bonded tog.

© 1998 LOGAL

First Ionization Energy

Energy required to remove one e- from a neutral atom.

© 1998 LOGAL

C. Other Properties

Atomic Radius

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0 5 10 15 20Atomic Number

Ato

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Ra

diu

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D. Atomic Radius

Li

ArNe

KNa

1

2

3

4 5

6

7

Atomic Radius Increases to the LEFT and DOWN

D. Atomic Radius

Why larger going down?

Higher energy levels have larger orbitals

Shielding - core e- block the attraction between the nucleus and the valence e-

Why smaller to the right?

Increased nuclear charge without additional shielding pulls e- in tighter

D. Atomic Radius

First Ionization Energy

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0 5 10 15 20Atomic Number

1st

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y (k

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E. Ionization Energy

KNaLi

ArNeHe ion: atom or

group of atomswith a (+) or (-) charge

ionization: any process that results in theformation of an ion

1

2

3

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First Ionization Energy Increases UP and to the RIGHT

E. Ionization Energy

Why opposite of atomic radius?

In small atoms, e- are close to the nucleus where the attraction is stronger

Why small jumps within each group?

Stable e- configurations don’t want to lose e-

E. Ionization Energy

Successive Ionization Energies

Mg 1st I.E. 736 kJ

2nd I.E. 1,445 kJ

Core e- 3rd I.E. 7,730 kJ

Large jump in I.E. occurs when a CORE e- is removed.

E. Ionization Energy

Al 1st I.E. 577 kJ

2nd I.E. 1,815 kJ

3rd I.E. 2,740 kJ

Core e- 4th I.E. 11,600 kJ

Successive Ionization Energies

Large jump in I.E. occurs when a CORE e- is removed.

E. Ionization Energy

1

2

3

4 5

6

7

Melting/Boiling Point Highest in the middle of a period.

F. Melting/Boiling Point

Ionic Radius

Cations (+)

lose e-

smaller

© 2002 Prentice-Hall, Inc.

Anions (–)

gain e-

larger

G. Ionic Radius

H. ELECTRON AFFINITY

electron affinity: (def) energy change that occurs when an electron is acquired by a neutral atom

A + e- A- + energy Energy released: negative value

Energy gained: positive value

H. ELECTRON AFFINITY

Trends: Among elements of each period, the

halogens gain electrons most readily.

(analogy of buying & selling)

As a general rule, electrons are added with more difficulty down a group.

H. ELECTRON AFFINITY

Adding Electrons to Negative Ions

It is always more difficult to add a 2nd electron to an already charged ion.

This makes all 2nd electron affinity values positive.

I. ELECTRONEGATIVITY

electronegativity: (def) a measure of the ability of an atom in a chemical compound (bonding) to attract electrons

TRENDS: Across a period, tend to increase

Down a group, tend to decrease or stay the same

J. VALENCE ELECTRONS

valence electrons: (def) electrons available to be lost, gained, or shared in the formation of chemical compounds

Which particle has the larger radius?

S or S2-

Al or Al3+

S2-

Al

Examples

Which atom has the higher 1st I.E.?

N or Bi

Ba or Ne

N

Ne

Examples

Which atom has the larger radius?

Be or Ba

Ca or Br

Ba

Ca

Examples

Which atom has the higher melting/boiling point?

Li or C

Cr or Kr

C

Cr

Examples

REVIEW QUESTION

Which of the following is the most reactive metal?

Neon, Boron, Beryllium, Lithium, Silicon

Lithium

REVIEW QUESTION

The element in period 3 with the largest atomic radius is:

Sodium, chlorine, magnesium, argon

Sodium

REVIEW QUESTION

Which of the following elements is most electronegative?

Phosphorus, Carbon, Chlorine, Boron, Iodine

Chlorine

REVIEW QUESTIONS

Which of the following has the most metallic character?

Fluorine, chlorine, Bromine, Iodine

Iodine

REVIEW QUESTIONS

Which ionization energy (1st, 2nd, 3rd, etc) will show a jump in value for an atom of Be?

3rd ionization energy

REVIEW QUESTIONS

Which electron affinity value will be more negative: for F or N?

F – most negative values (will spend the most money)

All second electron affinity values are: positive or negative?

positive