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WednesdayOctober 5, 2011
(Ionization Energy; Electron Affinity)
We will have a test next Tuesday.
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Assignment Currently Open
Summative or
Formative
Date Issued
Date Due
Date Into
Grade Book
Last Day
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
Bell RingerWednesday, 10-5-11
_______________ is the energy required to
remove one electron from a neutral atom
of an element.
Ionization energy
Bell RingerWednesday, 10-5-11
Ionization energy _______ from left to right across a period because of:
increases
Ionization energy ______ 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.
decreases
increasing nuclear charge. An increase in the number of protons
more strongly attracts electrons in the same energy level.
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 EnergyIn 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 energy required for an atom to lose electrons
increases as you move from left to
right across a period.
increases
Ionization EnergyAmong 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 RingerWednesday, 10-5-11
__________________ is the energy change that
occurs when an electron is acquired by a neutral
atom.
Electron affinity
Bell RingerWednesday, 10-5-11
Electron affinity _______ from left to right across a period because:
increases
Electron affinity _______ 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.
decreases
adding an electron to an empty sublevel takes less energy than adding electrons to a half-filled
sublevel.
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 AffinityIn 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.
negativity increases
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 half-filled p sublevel of a
oxygen atom.
Electron AffinityAs 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.”