Wednesday
October 5, 2011
(Ionization Energy;
Electron Affinity)
Announcements
We will have a test next
Tuesday.
Assignment Currently
Open
Summative
or
Formative
Date
Issued
Date
Due
WS – The Electromagnetic
Spectrum
F
9/23
9/27
WS – Average Atomic
Mass
F
9/27
9/29
WS – Periodic Properties
F
10/3
10/6
TEKSCheck #!
F
10/4
10/4
Date
Into
Grade
Book
Last
Day
Bell Ringer
Wednesday, 10-5-11
Ionization energy is the
_______________
energy required to remove
one electron from a neutral
atom of an element.
Bell Ringer
Wednesday, 10-5-11
Ionization energy increases
_______ from left to right across a
period because of:
increasing nuclear charge. An increase in the number
of protons more strongly attracts electrons in the same
energy level.
Ionization energy decreases
______ from top to bottom down
a group because:
electrons removed from atoms of each succeeding
element in a group are in higher energy levels, farther
from the nucleus.
Ionization Energy
Ionization energy may be defined as
the energy required to remove one
electron from a neutral atom of an
element.
This property determines the extent to which an
atom is capable of losing electrons in order to
begin the chemical bonding process.
Ionization Energy
In general, ionization energies of the main-group
elements increase across each period. This increase is
caused by increasing nuclear charge. A higher charge
more strongly attracts electrons in the same energy
level.
Generally
speaking, the
increases
energy required
for an atom to
lose electrons
increases as you
move from left to
right across a
period.
Ionization Energy
Among the main-group elements, ionization energies
generally decrease down the groups. Electrons
removed from atoms of each succeeding element in a
group are in higher energy levels, farther from the
nucleus.
Generally
speaking, the
energy required
to lose electrons
get less as you
move down a
group.
Therefore, they
are removed
more easily.
decrease
Bell Ringer
Wednesday, 10-5-11
Electron affinity is the
__________________
energy change that
occurs when an electron
is acquired by a neutral
atom.
Bell Ringer
Wednesday, 10-5-11
Electron affinity increases
_______ from left to right across a
period because:
adding an electron to an empty sublevel takes less
energy than adding electrons to a half-filled sublevel.
Electron affinity decreases
_______ from top to bottom down a
group because of:
a slight increase in effective nuclear charge down a
group, and an increase in atomic radius down a
group.
Electron Affinity
.
Electron affinity is defined as the energy
change that occurs when an electron is
acquired by a neutral atom.
Most atoms release energy when they acquire an
electron - the quantity of energy released is represented
by a negative number.
Some atoms must be “forced” to gain an electron by the
addition of energy - the quantity of energy absorbed is
represented by a positive number.
Electron Affinity
In general, as electrons add to the same p sublevel of
atoms with increasing nuclear charge, electron
affinities become more negative across each period
within the p block, although there are exceptions.
For example, adding
an electron to a
nitrogen atom gives
a half-filled p
sublevel. This
occurs much more
easily than forcing
an electron to pair
with another
electron in an orbital
of the already halffilled p sublevel of a
oxygen atom.
negativity increases
Electron Affinity
As a general rule, electrons add with greater difficulty down a
group. This pattern is a result of two competing factors.
The first is a slight increase in effective nuclear charge down
a group, which increases electron affinities. The second is
an increase in atomic radius down a group, which decreases
electron affinities.
In general,
the size effect
predominates.
decrease
Complete the worksheet
entitled “Periodic
Properties.”
Begin the worksheet
entitled “The Periodic Law.”