I II III

Periodic Trends

The Periodic Table

0

50

100

150

200

250

0 5 10 15 20Atomic Number

Ato

mic

Ra

diu

s (

pm

)

Periodic Law

When elements are arranged in order of

increasing atomic #, elements with similar

properties appear at regular intervals.

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50

100

150

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0 5 10 15 20

Ato

mic

Ra

diu

s (

pm

)

Atomic Number

Same number of valence electrons = similar properties

Li 1s2 2s1 Na 1s2 2s2 2p6 3s1

In any group, the element BELOW has one more occupied energy level than does the element ABOVE.

The period that an element is in is the same as the energy level that its valence electrons are in.

Li in 2nd period Na in 3rd period

val. e- in 2nd val e- in 3rd

Metallicity

More Metallic Less Metallic

Mo

re M

etal

lic

Les

s M

etal

lic

Periodic Trends and Factors

There are trends in properties of elements left right AND up down trends

Trends Atomic Radius Ionic Radius Ionization Energy Electronegativity

Factors: Columbic attraction and Sheilding effect

I II III

Periodic Factors

Coulombic attraction depends on…

2– 2+

2+ 2– 1–

2–

1+

2+

amount of charge distance between charges

+ + – –

H

He

+ –

+ – + –

As we go ,

more coulombic

attraction, no new

energy level, more

pull, smaller size

shielding effect: kernel e– “shield” valence e–

from attractive force of the nucleus

Li

v.e–

K

v.e–

-- caused by kernel and valence e–

repelling each other

As we go , shielding effect increases.

tougher to

removeeasier

to remove

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Atomic Radius

Atomic Radius

The size of a neutral atom Increases as we go down

Why?Add a new energy level each time (larger orbitals)

Decreases as we go across Why?

It has do to with coloumbic attraction (attraction between + and -)

Atomic Radius

Li

Na

K

Rb

Cs

ClSPSiAl

BrSeAsGeGa

ITeSbSnIn

Tl Pb Bi

Mg

Ca

Sr

Ba

Be FONCB

1.52 1.11

1.86 1.60

2.31 1.97

2.44 2.15

2.62 2.17

0.88 0.77 0.70 0.66 0.64

1.43 1.17 1.10 1.04 0.99

1.22 1.22 1.21 1.17 1.14

1.62 1.40 1.41 1.37 1.33

1.71 1.75 1.46

IA IIA IIIA IVA VA VIA VIIA

1

2

3

4

5

6

7

Decreases to the LEFT and increases DOWN

Atomic Radius

Which atom has the larger radius?

Be or Ba

Ca or Br

Ba

Ca

Examples

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Ionic Radius

Ionic Radius Cations (+)

lose e-

smaller

© 2002 Prentice-Hall, Inc.

Anions (–)

gain e-

larger

Ionic Radius

Ionic Radius

As you go down, the ionic radius increases due to more energy levels.

As you go across The ionic radius of metals decreases

until middle of periodic table, slight increase, and then decrease.

Due to lose or gain of electron

Which particle has the larger radius?

S or S2-

Al or Al3+

S2-

Al

Examples

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Ionization Energy

Ionization Energy

The energy required to remove an electron from an atom.

Each successive ionization requires more energy than the previous one.

As we go down, the first ionization energy decreases (due to shielding).

As we go across, the first ionization energy increases.

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.

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.

Ionization Energy

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

N or Bi

Ba or Ne

N

Ne

Examples

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Electronegativity

Electronegativity

Tendency of an atom to attract electrons in a chemical bond. Excludes noble gases.

As you go down, electronegativity decreases.

As you go across, the electronegativity increases.

Electronegativity

Why smaller going down? The higher the energy level, the less the

electron attraction of the atom.Why larger going across?

As the number of valence electrons increases, the electron attraction of the atom increases.

Electronegativity

Values Lowest values– metals at the far left

Lose electrons Highest values – nonmetals at the far

rightGain electrons

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Other Periodic Trends

1

2

3

4 5

6

7

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

Melting/Boiling Point

Which atom has the higher melting/boiling point?

Li or C

Cr or Kr

C

Cr

Examples

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Summary

Let’s Recap

Summary of Periodic Trends

Ionic size (cations) Ionic size (anions)

decreases decreases

Shielding is constant

Atomic radius decreases

Ionization energy increases

Electronegativity increases

Sh

ield

ing

in

crea

ses

Ato

mic

rad

ius

incr

ease

s

Ion

ic s

ize

incr

eas

es

Ion

izat

ion

en

erg

y d

ecre

ases

Ele

ctro

neg

ativ

ity

dec

reas

es

1A

2A 3A 4A 5A 6A 7A

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