I II III

III. Periodic Trends

(p. 140 - 154)

Ch. 6 - The Periodic Table

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A. Periodic Law

When elements are arranged in order of

increasing atomic #, elements with similar

properties appear at regular intervals. Each

interval corresponds to a family.

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Atomic Number

A. Know 6 Trends for TEST

M R E I R O increasing trends

Metallic Character: loosely held electrons

Radius (size of atom)

Electron Affinity (electronegativity)

Ionization Energy (first ionization E only)

Reactivity (bonding) of Metals losing e- or

Nonmetals gaining e-

Oxidation State (ionic charge)

A. Periodic Trends described

Most trends of chemical properties on the periodic table can be explained

by

Radius (size) of atom: effects the nuclear attraction, the

electromagnetic attraction of positive nucleus and negative electrons

Octet Rule: all atoms want to achieve 8 valence electrons, a stable noble

gas configuration and so will react (bond) in ways to do that

Metals will lose electrons to do this and Nonmetals will gain electrons

Metals = loosely held electrons causing properties like being malleable, ductile, luster, and good conductors of electricity and heat

Nonmetals = tightly held electrons making them be brittle, dull, and insulators (bad conductors)

Metalloids = have properties of both in different circumstances

B. Metallic Character M

M

Atomic Radius (size of atom) as # of shells increase the size gets bigger and the nuclear attraction (+ nucleus for –

electrons) for the valence electrons is decreased

© 1998 LOGAL

C. Radius R

Atomic Radius

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C. Atomic Radius

Li

ArNe

KNa

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2

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4 5

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7

Atomic Radius Increases to the LEFT and DOWN

C. Atomic Radius

Why larger atoms going down? Higher energy levels have larger shells further from nucleus

Shielding - core e- block the attraction between the nucleus and the valence e- alonging valence electrons to be lost more easily

Why smaller to the right? Increased nuclear charge within the same shell, without

additional shielding, pulls e- in tighter

C. Atomic Radius

Ionic Radius of

Cations (+)lose e- and become

smaller due to less

shells

Anions (–)gain e- and stay

about the same

size

C. Radius changes as neutral atoms become ions

Measure of the tendency to gain electrons (also called electronegativity)

Electron affinity is low for metals so easy to remove e-

Electron affinity is high for nonmetals due to smaller size and need a just a few more e- to reach the stable octet

D. Electron Affinity E

The Pauli Scale measures electronegativity on a scale of 0 to maximum of 4

D. Also called Electronegativity E

1

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4 5

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7

Increases UP and to the RIGHT

E. Electron Affinity

X

X

X

X

X

X

F

This is the amount of energy required to remove the first outer electron Ionization energy is low for metals so easy to remove electrons

Ionization is high for nonmetals and especially the noble gases because electrons are held tightly

E. Ionization Energy I

First Ionization Energy

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E. Ionization Energy

KNaLi

Ar

NeHe

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2

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4 5

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7

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 higher near the noble gases?

Stable e- configurations (or very close to 8 valence e-) 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

F. Chemical Reactivity R

Alkali Metals = most reactive metals, explosive with water Alkaline Earth Metals = also reactive Transition Metals = less reactive Halogens = most reactive nonmetals Noble Gases = inert, nonreactive

X

X

X

X

X

X

G. Oxidation State O

+3 +/- 4 -3 -2 -1

Families IA to VIIIA correspond to having that number of valence

electrons (remember all want 8 valence e)

Charges are positive when valence electrons are lost; Charges are

negative when valence e-’s are gained+1 +2

1

2

3

4 5

6

7

This is the general trend but…transition metals can have a range of charges from +1 to +7

G. Oxidation State

+ -

C

1

2

3

4 5

6

7

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

H. Melting/Boiling Point

Which atom has the larger radius?

Be or Ba

Ca or Br

Ba

Ca

Examples

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

N or Bi

Ba or Ne

N

Ne

Examples

Which atom can have an oxidation state of +1?

Li or C

S or Kr

Li

S

Examples

Which atom can have an oxidation state of -2?

Which particle has the larger radius?

S or S2-

Al or Al3+

S2-

Al

Examples