Coulomb’s Law
 Addresses the force of attraction between the positive
nucleus and negative electron
 F = qe qp
r2
qe = charge of electron
qp = charge of nucleus
 INVERSE relationship between attractive force and
distance
 Attractive force is DIRECTLY related to the charge on
the electron and the charge in the nucleus
First Ionization Energy (IE)
 If an electron is given enough energy (in the form of a
photon) to overcome the effective nuclear charge holding
the electron in the cloud, it can leave the atom completely.
 Energy required to remove the outermost electron from an
atom
 Amount of energy needed to remove ONE electron from a
neutral atom
 Energy needed to remove electrons from ground state to
gaseous state in an atom
 Formation of positive ions (cations)
Ionization Energy (cont.)
 Formation of positive ions (cations)
 The larger the atom is, the easier its electrons are to
remove.
 Ionization energy and atomic radius are inversely
proportional.
Ionization Energy Trend
Increases
Decreases
Element
Atomic #
IE (kJ/mol)
Na
11
495.8
Mg
12
737.7
Al
13
577.6
S
16
999.6
Cl
17
1251.1
Ar
18
1520.5
K
19
418.8
Ionization Energy (cont.)
 1st ionization energy
 Energy required to remove 1st electron from atom
 Taken from highest energy level
 Easiest to remove
 Energy increases as more electrons are removed
Can we have 2nd, 3rd, 4th,
etc. Ionization Energies?
 Energy needed to remove additional electrons from an
atom
 Energy increases as more electrons are removed.
 Removing electrons from lower energy levels, close to
nucleus
Na
1st IE
2nd IE
3rd IE
4th IE
495.8
4562.4
6912
9543
Ionization Energy
Example 1:
Place these elements in order of INCREASING 1st ionization energy.
1) Mg, S, Si
2) As, N, P
(p. 321 in text)
What does affinity
mean?
Electron Affinity
 Creating negative ions (anions)
 Energy change with the addition of an electron to an
atom
 energy change that occurs when electrons added to gaseous
atom
 Energy is released when electrons are added,
exothermic process (negative value)
Electron Affinity
 Electron tends to enter partially filled subshell or go to the next energy
level
 Does not follow predictable trend like atomic radii and ionization
energy
 An atom’s “desire/affinity” for more electrons, wants to get more
electrons ! ! !
 Metals—decrease electron affinity.
 Nonmetals—increase electron affinity, more reactive
 Stable atoms—full octet
Electron Affinity Trend
Increases
Decreases
Homework
 Atomic Theory III Worksheet #1-21 due Thursday !!!