ELECTRON CONFIGURATIONS AND PERIODIC PROPERTIES

Chapter 5.3

Objectives:

1. Define atomic radii and ionic radii, ionization energy, electron affinity, and electronegativity.

2. Compare periodic trends for these properties and state reasons for variations.

3. Define valence electrons, and state how many are present in atoms of each main-group element.

4. Compare the these same properties of d-block elements with those of the main-group elements

Atomic Radii Defined as one-half

the distance between the nuclei of identical atoms that are bonded together

Period trends Decrease from left to

right Due to increasing

positive charge

Group trends Increase down a

group Due to occupying

higher energy levels

Atomic Radii

Ionization Energy Defined as energy

required to remove one electron from a neutral atom of an element (IE)

A + energy A+ + e-

Ion – atom or group of bonded atoms that has a positive or negative charge.

Ionization Energy Period trends

Generally increase across a period Due to increasing nuclear

charge Group trends

Generally decrease down a group Due to electron shielding of

outer electrons

Electron Affinity Defined as the

energy change that occurs when an electron is acquired by a neutral atom

A + e- A- + energy

Quantity released represented by a negative number

A + e- + energy A-

Quantity absorbed represented by a positive number

•Forced •Unstable

Ionic radii Cation – positive ion

Formed by loss of one or more electrons Smaller due to removal

of electron & stronger pull by nucleus on remaining electrons

Ionic Radii

Anion– negative ion Formed by gain of one

or more electrons Larger due to addition

of electron & remaining electrons are not pulled as strongly by nucleus

Valence Electrons Defined as the electrons available

to be lost, gained, or shared in the formation of chemical compounds

Sodium atom

Chlorine atom

Valence electron

Valence Electrons

s

s s

s s

s s

s s

s s

s s

1 2 3 4 5 6 7 8

Electronegativity Defined as the measure of

the ability of an atom in a chemical compound to attract electrons Want to gain electrons!!

Noble gases have very low electronegativity

Alkali metals are low as well Halogens have the highest Electronegativi

ty Period trends Tend to increase across a period

Due to wanting to fill outer shell

Group trends Tend to decrease down a

group

Electronegativity

2.1H

1.0Li

1.5Be

2.0B

2.5C

3.0N

3.5O

4.0F

1.0Na

1.2Mg

1.5Al

1.8Si

2.1P

2.5S

3.0Cl

0.9K

1.0Ca

1.3Sc

1.4Ti

1.5V

1.6Cr

1.6Mn

1.7Fe

1.7Co

1.8Ni

1.8Cu

1.6Zn

1.7Ga

1.9Ge

2.1As

2.4Se

2.8Br

0.9Rb

1.0Sr

1.2Y

1.3Zr

1.5Nb

1.6Mo

1.7Tc

1.8Ru

1.8Rh

1.8Pd

1.6Ag

1.6Cd

1.6In

1.8Sn

1.9Sb

2.1Te

2.5I

0.8Cs

1.0Ba

1.1La

1.3Hf

1.4Ta

1.5W

1.7Re

1.9Os

1.9Ir

1.8Pt

1.9Au

1.7Hg

1.6Tl

1.7Pb

1.8Bi

1.9Po

2.1At

0.8Fr

1.0Ra

1.1Ac